# Expansion of RCRA Comparable Fuel Exclusion

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URL: https://www.frixlaw.com/law-library/documents/fr%3AE7-11130

## Record

- **Collection:** Federal Register
- **Document type:** Proposed Rule
- **Published:** June 15, 2007
- **Citation:** 72 FR 33284

## Text

ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 261
[EPA-HQ-RCRA-2005-0017; FRL-8324-2]
RIN 2050-AG24
Expansion of RCRA Comparable Fuel Exclusion

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

EPA is proposing to expand the comparable fuel exclusion under the rules implementing subtitle C of the Resource Conservation and Recovery Act (RCRA) for fuels that are produced from hazardous waste but which generate emissions that are comparable to emissions from burning fuel oil when such fuels are burned in an industrial boiler. Such excluded fuel would be called emission-comparable fuel (ECF). ECF would be subject to the same specifications that currently apply to comparable fuels, except that the specifications for certain hydrocarbons and oxygenates would not apply. The ECF exclusion would be conditioned on requirements including: Design and operating conditions for the ECF boiler to ensure that the ECF is burned under the good combustion conditions typical for oil-fired industrial boilers; and conditions for tanks storing ECF which conditions are typical of those for storage of commercial fuels, and are tailored for the hazards that ECF may pose.

DATES:

Comments must be received on or before August 14, 2007. Under the Paperwork Reduction Act, comments on the information collection provisions must be received by OMB on or before July 16, 2007.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-HQ-RCRA-2005-0017, by one of the following methods:

•
http://www.regulations.gov:
Follow the on-line instructions for submitting comments.

•
E-mail: rcra-docket@epa.gov.

•
Fax:
202-566-9744.

•
Mail:
RCRA Docket, Environmental Protection Agency, Mailcode: 2822T, 1200 Pennsylvania Ave., NW., Washington, DC 20460. Please include a total of two copies. We request that you also send a separate copy of your comments to the contact person listed below (see
FOR FURTHER INFORMATION CONTACT
). In addition, please mail a copy of your comments on the information collection provisions to the Office of Information and Regulatory Affairs, Office of Management and Budget (OMB), Attn: Desk Officer for EPA, 725 17th St., NW., Washington, DC 20503.

•
Hand Delivery:
RCRA Docket, EPA Docket Center (2822T), EPA West, Room 3334, 1301 Constitution Ave., NW., Washington, DC. Such deliveries are only accepted during the Docket's normal hours of operation, and special arrangements should be made for deliveries of boxed information. Please include a total of two copies. We request that you also send a separate copy of each comment to the contact person listed below (see
FOR FURTHER INFORMATION CONTACT
).

Instructions:
Direct your comments to Docket ID No. EPA-HQ-RCRA-2005-0017. EPA's policy is that all comments received will be included in the public docket without change and may be made available online at
http://www.regulations.gov
, including any personal information provided, unless the comments include information claimed to be Confidential Business Information (CBI) or other information the disclosure of which is restricted by statute. Do not submit information that you consider to be CBI or otherwise protected through
http://www.regulations.gov
or e-mail. Send or deliver information identified as CBI to the following address: Ms. LaShan Haynes, RCRA Document Control Officer, EPA (Mail Code 5305P), Attention Docket ID No. EPA-HQ-RCRA-2005-0017, 1200 Pennsylvania Avenue, NW., Washington, DC 20460. Clearly mark the part or all of the information that you claim to be CBI. The
http://www.regulations.gov
Web site is an “anonymous access” system, which means EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an e-mail comment directly to EPA without going through
http://www.regulations.gov
, your e-mail address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD-ROM you submit. If EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, EPA may not be able to consider your comment. Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses. For additional information about EPA's public docket, visit the EPA Docket Center homepage at
http://www.epa.gov/epahome/dockets.htm.
We also request that interested parties who would like information they previously submitted to EPA to be considered as part of this action identify the relevant information by docket entry numbers and page numbers.

Docket:
All documents in the docket are listed in the
http://www.regulations.gov
index. Although listed in the index, some information is not publicly available, e.g., CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy. Publicly available docket materials are available either electronically in
http://www.regulations.gov
or in hard copy at the RCRA Docket, EPA/DC, EPA West, Room 3334, 1301 Constitution Ave., NW., Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Public Reading Room is (202) 566-1744, and the telephone number for the RCRA Docket is (202) 566-0270.

FOR FURTHER INFORMATION CONTACT:

Mary Jackson, Hazardous Waste Minimization and Management Division, Office of Solid Waste, Mailcode: 5302P, Environmental Protection Agency, 1200 Pennsylvania Ave., NW., Washington, DC 20460; telephone number: (703) 308-8453; fax number: (703) 308-8433; e-mail address:
jackson.mary@epa.gov.

SUPPLEMENTARY INFORMATION:

General Information

A. Does This Action Apply to Me?

Categories and entities potentially affected by this action include:

Category
NAICS code
SIC code
Examples of potentially regulated entities

Any industry that generates or combusts hazardous waste as defined in the proposed rule
562
49
Waste Management and Remediation Services.

327
32
Non-metallic Mineral Products Manufacturing.

325
28
Chemical Manufacturing.

324
29
Petroleum and Coal Products Manufacturing.

331
33
Primary Metals Manufacturing.

333
38
Machinery Manufacturing.

326
306
Plastic and Rubber Products Manufacturing.

488, 561
49
Administration and Support Services.

421
50
Scrap and waste materials.

422
51
Wholesale Trade, Non-durable Goods, N.E.C.

512, 541, 812
73
Business Services, N.E.C.

512, 514, 541, 711
89
Services, N.E.C.

924
95
Air, Water and Solid Waste Management.

336
37
Transportation Equipment Manufacturing.

928
97
National Security.

334
35
Computer and Electronic Products Manufacturing.

339
38
Miscellaneous Manufacturing.

This table is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be impacted by this action. This table lists examples of the types of entities EPA is now aware could potentially be regulated by this action. Other types of entities not listed could also be affected. To determine whether your facility, company, business, organization, etc., is affected by this action, you should examine the applicability criteria in this proposed rule. If you have any questions regarding the applicability of this action to a particular entity, consult the person listed in the preceding
FOR FURTHER INFORMATION CONTACT
section.

B. What Should I Consider as I Prepare My Comments for EPA?

1. Submitting CBI. Do not submit this information to EPA through
http://www.regulations.gov
or e-mail. Clearly mark the part or all of the information that you claim to be CBI. For CBI information in a disk or CD ROM that you mail to EPA, mark the outside of the disk or CD ROM as CBI and then identify electronically within the disk or CD ROM the specific information that is claimed as CBI. In addition to one complete version of the comment that includes information claimed as CBI, a copy of the comment that does not contain the information claimed as CBI must be submitted for inclusion in the public docket. Information so marked will not be disclosed except in accordance with procedures set forth in 40 CFR part 2.

2. Tips for Preparing Your Comments. When submitting comments, remember to:

• Identify the rulemaking by docket number and other identifying information (subject heading,
Federal Register
date and page number).

• Follow directions—The agency may ask you to respond to specific questions or organize comments by referencing a Code of Federal Regulations (CFR) part or section number.

• Explain why you agree or disagree; suggest alternatives and substitute language for your requested changes.

• Describe any assumptions and provide any technical information and/or data that you used.

• If you estimate potential costs or burdens, explain how you arrived at your estimate in sufficient detail to allow for it to be reproduced.

• Provide specific examples to illustrate your concerns, and suggest alternatives.

• Explain your views as clearly as possible, avoiding the use of profanity or personal threats.

• Make sure to submit your comments by the comment period deadline identified.

3. Docket Copying Costs:

You may copy a maximum of 100 pages from any regulatory docket at no charge. Additional copies are 15 cents/page.

4. How Do I Obtain a Copy of This Document and Other Related Information?

In addition to being available in the docket, an electronic copy of today's proposed rule will also be available on the Worldwide Web (WWW). Following the Administrator's signature, a copy of this document will be posted on the WWW at
http://www.epa.gov/hwcmact.
This Web site also provides other information related to the NESHAP for hazardous waste combustors.

5. Index of Contents

The information presented in this preamble is organized as follows:

Part One: Background and Summary

I. Statutory Authority

II. Background

A. What Is the Intent of This Proposed Rule?

B. Who Would Be Affected by This Proposed Rule?

C. What Is the Relationship Between the Proposed Rule and the Existing Exclusion for Comparable Fuel?

1. What Modifications to the Comparable Fuel Exclusion May Be Warranted?

2. How Has EPA Involved Stakeholders in Discussions Regarding Potential Revisions to the Comparable Fuel Exclusion?

III. Summary of the Proposed Rule

A. What Are the Conditions for Exclusion of Emission-Comparable Fuel (ECF)?

B. What Changes Is EPA Proposing to the Conditions for Existing Comparable Fuel?

Part Two: Rationale for the Proposed Rule

I. What Is the Rationale for Excluding Emission-Comparable Fuel From the Definition of Solid Waste?

A. Why Would the Specifications Be Waived Only for Hydrocarbons and Oxygenates?

B. Do Available Data and Information Support a Comparable Emissions Finding?

1. Evaluation of Organic Emissions Data for Hazardous Waste Boilers

2. Evaluation of RCRA Risk Assessments

3. Comparative Risk Assessment for Dioxin/Furan

II. What Conditions Would Apply to Burners of Emission-Comparable Fuel?

A. Why Isn't a DRE Performance Test a Critical Requirement To Ensure Good Combustion Conditions?

B. What Is the Rationale for the Proposed Burner Conditions?

1. ECF Must Be Burned in a Watertube Steam Industrial or Utility Boiler That Is Not Stoker-Fired

2. CO Monitoring

3. The Boiler Must Fire at Least 50% Primary Fuel

4. The Boiler Load Must Be 40% or Greater

5. The ECF Must Have an As-Fired Heating Value of 8,000 Btu/lb or Greater

6. ECF Must Be Fired Into the Primary Fuel Flame Zone

7. The ECF Firing System Must Provide Proper Atomization

8. Dioxin/Furan Controls for Boilers Equipped With an ESP or FF

III. What Restrictions Would Apply to Particular Hydrocarbons and Oxygenates?

A. What Is the Rationale for the Relative Hazard Characterization Scheme?

B. What Are the Results of the Relative Hazard Ranking?

C. What Firing Rate Restrictions Would Apply to Benzene and Acrolein?

IV. What Conditions Would Apply to Storage of ECF?

A. What Are the Proposed Storage Conditions?

1. Tank Systems, Tank Cars and Tank Trucks

2. Underground Storage Tank Systems

3. Closure of Tank Systems

4. Waiver of RCRA Closure for RCRA Tanks That Become ECF Tanks

5. Management of Incompatible Waste Fuels and Other Materials

B. What Other Options Did We Consider?

1. Other Options We Considered to Establish Storage Conditions for ECF

2. Consideration of Storage Controls for Currently Excluded Comparable Fuels

V. How Would We Assure That The Conditions Are Being Satisfied?

A. What Recordkeeping, Notification and Certificate Conditions Would Apply to Generators and Burners?

1. Waste Analysis Plans

2. Sampling and Analysis

3. Speculative Accumulation

4. Notifications

5. Burner Certification

6. Recordkeeping

7. Transportation

8. Ineligible RCRA Hazardous Waste Codes

B. What If I Fail To Comply With Conditions of the Exclusion?

C. How Would Spills and Leaks Be Managed?

D. What Would Be the Time-Line for Meeting the Proposed Conditions?

VI. What Clarifications and Revisions Are Proposed for the Existing Conditions for Exclusion of Comparable Fuel?

VII. What Are the Responses to Major Comments of the Peer Review Panel?

A. What Are the Reponses to Major Comments Regarding the Comparable Emissions Rationale?

B. What Are the Reponses to Major Comments Regarding the Application of the WMPT To Rank Comparable Fuel Constituents?

Part Three: State Authority

I. Applicability of the Rule in Authorized States

II. Effect on State Authorization

Part Four: Costs and Benefits of the Proposed Rule

I. Introduction

II. Baseline Specification

III. Analytical Methodology, Primary Data Sources, and Key Assumptions

IV. Key Analytical Limitations

V. Findings

Part Five: Statutory and Executive Order Reviews

I. Executive Order 12866: Regulatory Planning and Review

II. Paperwork Reduction Act

III. Regulatory Flexibility Act

IV. Unfunded Mandates Reform Act of 1995

V. Executive Order 13132: Federalism

VI. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments

VII. EO 13045 “Protection of Children From Environmental Health Risks and Safety Risks”

VIII. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use

IX. National Technology Transfer Advancement Act

X. Executive Order 12898: Federal Actions To Address Environmental Justice in Minority Populations and Low-Income Populations

Part One: Background and Summary

I. Statutory Authority

These regulations are proposed under the authority of sections 2002, 3001, 3002, 3003, and 3004 of the Solid Waste Disposal Act of 1970, as amended by the Resource Conservation and Recovery Act of 1976 (RCRA), as amended by the Hazardous and Solid Waste Amendments of 1984 (HSWA), 42 U.S.C. 6921, 6922, 6923, and 6924.

II. Background

A. What Is the Intent of This Proposed Rule?

Section 40 CFR 261.38 states that secondary materials (
i.e.
, materials that otherwise would be hazardous wastes) which have fuel value and whose hazardous constituent levels are comparable to those found in the fossil fuels which would be burned in their place are not solid wastes, and hence not hazardous wastes. We are proposing to amend the comparable fuel exclusion by expanding the exclusion to include fuels that are produced from a hazardous waste but which generate emissions when burned in an industrial boiler that are comparable to emissions from burning fuel oil. In other words, the fuels would be comparable from an emissions standpoint but not a physical standpoint. The revised rule would establish a new category of excluded waste-derived fuel called emission-comparable fuel (ECF).

The quantity of waste fuels excluded under this approach would increase substantially the amount of hazardous waste fuels that would eligible for exclusion from the RCRA hazardous waste regulations. Specifically, we estimate that approximately 13,000 tons per year of waste fuels are currently excluded under the existing comparable fuel exclusion, while we project that up to an additional 107,000 tons per year may be excluded under the exclusion being proposed today.

These additional hazardous secondary materials could be burned for energy recovery without imposing unnecessary regulatory costs on generators, primarily the manufacturing sector. However, the expanded comparable fuel exclusion may not substantially increase the amount of hazardous waste burned for energy recovery because high Btu wastes, even though not currently excluded from RCRA, are currently burned in industrial furnaces and incinerators for their fuel value. Nonetheless, continuing to regulate these waste-derived fuels as hazardous wastes would treat a potentially valuable fuel commodity (especially considering the increasing value of fuels) as a waste without a compelling basis.

B. Who Would Be Affected by This Proposed Rule?

Entities that generate, burn, and store ECF are potentially affected by this proposal. The basic structure of the proposal is that ECF is no longer a solid (and hazardous) waste, and hence that each of these entities would not be subject to subtitle C regulation when managing ECF. Thus, generators of hazardous waste fuels that meet the conditions of the ECF exclusion could manage these fuels without being subject to subtitle C regulation assuming that the management conditions are satisfied. Burners, which are limited to certain industrial boilers (including utility boilers), could burn ECF provided the boilers meet the design and operating conditions in the proposed rule, as discussed in Part II, Section II. Generators would benefit from lower operating costs because of lower (or eliminated) waste management fees and because these fuels would substitute for fuels which would otherwise be purchased. In addition, entities storing ECF would not be subject to subtitle C standards provided they satisfy the management conditions tailored to ECF, as discussed in Part Two, Section IV.

Commercial hazardous waste combustors that are currently managing waste fuels that qualify as ECF, on the other hand, might find themselves unable to continue to charge hazardous waste management fees for the excluded waste fuels. Consequently, commercial hazardous waste combustors might lose the waste management revenues for those diverted fuels and may need to meet their heat input requirements by using other waste fuels or fossil fuels.

C. What Is the Relationship Between the Proposed Rule and the Existing Exclusion for Comparable Fuel?

On June 19, 1998 (63 FR 33782 and § 261.38), EPA promulgated standards to exclude from the regulatory definition of solid waste certain hazardous waste-derived fuels that meet specification levels for hazardous constituents and physical properties that affect burning which are comparable to the same levels in fossil fuels. EPA's goal was to develop a comparable fuel specification which is useable by the regulated community, but assures that an excluded waste-derived fuel is similar in composition to commercially available fuel and therefore poses no greater risk than burning fossil fuel.

During the eight years that the comparable fuel exclusion has been part of the hazardous waste regulations, several stakeholders have pointed out that many hazardous wastes with fuel value do not satisfy the terms of the exclusion. Independently, in 2003, EPA began examining the effectiveness of the current comparable fuel program as part of an effort to promote the energy conservation component of the Resource Conservation Challenge
1

to determine whether other hazardous wastes could be appropriately excluded as comparable fuel.

1

See http://www.epa.gov/epaoswer/osw/conserve/strat-plan/strat-plan.htm#rccplan
.

As part of this effort, we contacted the American Chemistry Council (ACC) in early 2003 to determine how much waste is currently excluded as comparable fuel and whether there were additional quantities of other high Btu wastes that could potentially be considered comparable fuel. ACC conducted a survey of its members and provided results to EPA in late 2003 indicating that approximately 13,000 tons per year of waste fuels are currently excluded, but that approximately 190,000 tons per year of additional waste fuels could potentially be excluded under revisions to the exclusion.
2

2
Letter from American Chemistry Council (Carter Lee Kelly, Leader, Waste Issues Team, and Robert A. Elam, Director, Regulatory Affairs, Waste Issues Team) to Robert Springer and Matt Hale, USEPA, dated November 24, 2003.

Therefore, ACC recommended that EPA consider approaches to address the following barriers perceived as excluding additional quantities of waste fuels:

•
Analytic Issues:
High analysis cost and matrix interferences hamper meeting the detection limit requirements for nondetected analytes in many waste fuel matrices.

•
Over-Rigid Specifications:
Wastes containing nonhalogenated organics and oxygenates do not result in emissions greater than burning waste fuel meeting the specification if the combustor operates under good combustion conditions.

•
Blending:
The current exclusion bans blending to meet hazard constituent specifications. Flexibility is needed on blending of streams containing low levels of constituents, such as chromium and manganese attributable to corrosion from stainless steel vessels and pipes.

1. What Modifications to the Comparable Fuel Exclusion May Be Warranted?

We are proposing in this action to expand the exclusion for comparable fuel to establish a new category of excluded fuel—emission-comparable fuel (ECF). This proposal would exclude waste fuels that generate emissions, when burned in an industrial boiler, which are comparable to emissions from burning fuel oil. ECF would be subject to the same hazardous constituent and other specifications in Table 1 to § 261.38 that currently apply to comparable fuels, except that the specifications for certain hydrocarbons and oxygenates would not apply. The exclusion would be based on the rationale that ECF has substantial fuel value, that the hydrocarbon and oxygenate constituents no longer subject to a specification add fuel value, and that emissions from burning ECF in an industrial boiler operating under good combustion conditions are likely not to differ from emissions from burning fossil fuels under those same conditions. As a result, the current specifications limiting the hydrocarbons and oxygenates appear to be unnecessary.

The exclusion would be conditioned on the ECF being burned and stored under certain conditions, including: (1) Design and operating conditions for the ECF boiler that ensure that the ECF is burned under the good combustion conditions typical for oil-fired industrial boilers; and (2) conditions for storage in tanks which are comparable to those for storage of fuels and organic liquids and which are tailored for the hazards that ECF may pose given that ECF can have higher concentrations of certain hydrocarbons and oxygenates than fuel oil and gasoline.

We are not proposing revisions to the comparable fuel exclusion to address the analytical and blending recommendations raised by ACC.

a. Why Are We Not Proposing Revisions To Address Analytic Concerns?
The specifications in Table 1 to § 261.38 for volatile organic compounds that were not detected in fuel oil or gasoline were based on the low levels of detection achievable for fuel oil rather than the much higher levels of detection achievable for gasoline. Given that only benzene, toluene, and naphthalene were detected, EPA used this approach for most of the volatile organic compounds. EPA acknowledged this deviation from establishing the specification for nondetected compounds as the highest level of detection in a benchmark fuel and explained that the levels of detection for volatile compounds in gasoline were inflated because of matrix effects. ACC suggested that EPA consider the fact that many waste fuels may pose the same matrix effects as gasoline, such that the fuel oil-based specifications would not be reasonably achievable.

We believe that it would not be appropriate to consider increasing the specifications for all volatile organic compounds and base them on the higher levels of detection in gasoline rather than fuel oil levels of detection because most of the compounds would simply not be expected to be found in fuel oil or gasoline. Rather, only certain hydrocarbons would be expected to be in these fuels. We could potentially also consider oxygenates, however, because they are within a class of compounds that are added to fuels to enhance combustion. It appeared, however, that this revision would not likely result in additional hazardous waste fuel being conditionally excluded. There were very few, if any, waste fuels that meet the specifications for all volatile compounds, except for the enumerated hydrocarbons and oxygenates, and that also could meet revised, higher specifications for the hydrocarbons and oxygenates based on the levels of detection in gasoline. Consequently, we are not pursuing this approach further but, nonetheless, solicit comment on such an approach.

b. Why Are We Not Proposing Revisions To Address Blending Concerns?
A condition of the existing comparable fuel exclusion is that blending to meet the specification (except for viscosity) is prohibited to preclude dilution to avoid treatment.
3

ACC noted that waste fuels often contain incidental contamination of metals, such as chromium and manganese from corrosion of stainless steel vessels and pipes, and that blending to meet the specifications for

low levels of metals appears reasonable. We believe that blending to meet the specifications for metals is explicitly prohibited because it would be inconsistent with the section 3004(m) hazardous waste treatment provisions (which, although not directly applicable, articulate important overall statutory objectives) which require hazardous constituents to be removed or destroyed by treatment, not diluted. See 63 FR at 33795.

3
See 63 FR at 33795, and existing § 261.38(c)(3-4).

We believe, however, that blending to meet the specification for organic compounds that may be present in fuel oil or gasoline—hydrocarbons—or that are within a class of compounds that are added to fuels to enhance combustion—oxygenates—could be considered. These compounds would not be diluted to avoid treatment; they would still be treated by combustion. However, it appears that there were very few, if any, additional waste fuels that would be excluded under such a blending provision. Nonetheless, we solicit comment on such an approach and its applicability to additional waste fuels.

2. How Has EPA Involved Stakeholders in Discussions Regarding Potential Revisions to the Comparable Fuel Exclusion?

On December 15, 2005, EPA convened a public meeting of stakeholders to discuss potential revisions to the comparable fuel exclusion under 40 CFR 261.38.
4

Meeting notes are available in the docket for this rulemaking.
5

Participants in the stakeholder meeting raised several issues during the meeting and our responses are included in the meeting notes. In addition, several participants submitted written comments after the meeting. These comments and our responses are available in the docket to today's proposal.
6

4
See e-mail from Jim Berlow, USEPA, to Jim Pew, Earthjustice; Melvin Keener, Coalition for Responsible Waste Incineration; David Case, Environmental Technology Council; Michael Benoit, Cement Kiln Recycling Coalition; Barbara Simcoe, Association of State and Territorial Solid Waste Management Officials; and Robert Elam, American Chemistry Council, dated November 23, 2005.

5
See memorandum from Bob Holloway, USEPA, to Docket Number RCRA 2005-0017, entitled “Meeting Notes—Comparable Fuel Stakeholder Meeting on Dec. 15, 2005,” dated January 4, 2006.

6
USEPA, “Response to Comments on the December 15, 2005 Stakeholder Meeting Regarding Expanding the Comparable Fuel Exclusion,” May 2007.

III. Summary of the Proposed Rule

Today's proposed rule would expand the comparable fuel exclusion by conditionally waiving the specifications for certain hydrocarbons and oxygenates listed in Table 1 to § 261.38. This excluded waste fuel would be called emission-comparable fuel. We are also proposing to clarify the regulatory status of existing comparable fuel that no longer meets the conditions of the exclusion.

A. What Are the Conditions for Exclusion of Emission-Comparable Fuel (ECF)?

ECF is a fuel derived from hazardous waste but which would be excluded from the RCRA hazardous waste regulations if it meets prescribed specifications and management conditions. The ECF specifications would be the same as those that are applicable to comparable fuel, except the specifications for particular hydrocarbons and oxygenates would not apply. See proposed § 261.38(a)(2). The exclusion would apply from the point that ECF meets the specifications.

Special conditions of the exclusion specific to ECF would include the following design and operating conditions for the ECF burner: (1) The burner must be a watertube steam boiler other than a stoker-fired boiler; (2) carbon monoxide (CO) must be monitored continuously, must be linked to an automatic ECF feed cutoff system, and must not exceed 100 ppmv on an hourly rolling average (corrected to 7% oxygen); (3) the boiler must fire at least 50% primary fuel on a heating value or volume basis, whichever results in a higher volume of primary fuel, and the primary fuel must be fossil fuel or tall oil with a heating value not less than 8,000 Btu/lb; (4) the boiler load must be 40% or greater; (5) the ECF must have an as-fired heating value of 8,000 Btu/lb or greater; (6) ECF must be fired into the primary fuel flame zone; (7) the ECF firing system must provide proper atomization; and (8) if the boiler is equipped with an electrostatic precipitator (ESP) or fabric filter (FF) and does not fire coal as the primary fuel, the combustion gas temperature at the inlet to the ESP or FF must be continuously monitored, must be linked to the automatic ECF feed cutoff system, and must not exceed 400 °F on an hourly rolling average. See proposed § 261.38(c)(2). (Please note that we specifically request comment on these proposed conditions, as discussed later.) The principal conditions that would apply to ECF boilers—waterwall steam boiler, low CO, burning high Btu primary fuel that is properly atomized, operating at boiler loads above 40%—reflect design and operating conditions typical for oil-fired industrial boilers that operate under good combustion conditions.

In addition, ECF must be stored in tanks, tank cars, or tank trucks. See proposed § 261.38(c)(1). These tank systems, tank cars, and tank trucks would be excluded from regulation if they meet conditions similar to those which apply to fuel oil (the product most analogous to ECF), along with additional conditions necessary to minimize the potential for releases to the environment accounting for the differences between ECF and fuel oil. These include: (1) Certain provisions of the Spill Prevention, Control, and Countermeasures (SPCC) requirements applicable to oil under §§ 112.2, 112.5, 112.7, and 112.8; (2) secondary containment and leak detection requirements for tank systems, including use of liners, vaults, or double-walled tanks; (3) preparedness and prevention, emergency procedures, and response to release provisions adopted from requirements applicable to tank systems that store hazardous waste, and (4) fugitive air emission technical controls adopted from Subpart EEEE, Part 63, for organic liquids distribution (which would apply not only to any hazardous air pollutants among the oxygenates and hydrocarbons, but also would apply to the 11 oxygenates for which there would be no specification in this proposed rule and which are hazardous constituents under RCRA having significant vapor pressure but which are not hazardous air pollutants under the CAA). Underground tanks storing ECF are subject to the applicable requirements of 40 CFR Part 280. A further condition of the exclusion is that the generator must document in the waste analysis plan how precautions will be taken to prevent mixing of ECF and other materials which could result in adverse consequences from incompatible materials. In addition, to be excluded, ECF would need to meet all of the conditions applicable to existing comparable fuel, including: (1) The specifications under Table 1 to 261.38, except for the specifications for certain hydrocarbons and oxygenates; (2) prohibition on blending to meet the specifications, except for viscosity;
7

(3) notifications to state RCRA and Clean Air Act (CAA) Directors and public notification; (4) waste analysis plans; (5) sampling and analysis conditions; (6) prohibition on speculative accumulation; (7) recordkeeping; (8)

burner certification to the generator; and (9) ineligible waste codes.

7
ECF must have a heating value of 5,000 Btu/lb or greater as-generated (or after bona fide treatment), but must have a heating value of 8,000 Btu/lb, as fired. Thus, ECF with an as-generated heating value below 8,000 Btu/lb may be blended with other fuels to achieve a heating value of 8,000 Btu/lb.

ECF that has lost its exclusion because of failure to satisfy a condition of the exclusion must be managed as a hazardous waste from the point of ECF generation.
8

In addition, ECF that is spilled or leaked and cannot be burned under the conditions of the exclusion is a waste (it is a hazardous waste if it exhibits a characteristic of hazardous waste or if the ECF were derived from a listed hazardous waste) and must be managed in accordance with existing federal and state regulations. Furthermore, if an ECF tank system ceases to be operated to store ECF product, but has not been cleaned by removing all liquids and accumulated solids within 90 days of cessation of ECF storage operations, the tank system would become subject to the RCRA subtitle C hazardous waste regulations.
9

(This is the same principle that applies to any product storage unit when it goes out of service. See § 261.4(c).) Liquids and accumulated solids removed from a tank system that ceases to be operated for storage of ECF product are waste (they are hazardous wastes if they exhibit a characteristic of hazardous waste or if the ECF were derived from a listed hazardous waste).

8
Please note that we request comment on whether the final rule should include a “reasonable efforts” provision that would provide that the failure of an off-site, unaffiliated burner to meet the proposed conditions or restrictions of the exclusion would not mean the material was considered waste when handled by the generator, as long as the generator can adequately demonstrate that he has made reasonable efforts to ensure that the material will be managed by the burner under the conditions of the exclusion. See discussion in Part Two, Section V.B of the preamble.

9
If the tank is used to actively accumulate hazardous waste after being taken out of service as an ECF product tank, the tank may be eligible for the provisions under § 262.34 that waive the permit requirements for generator tanks that accumulate hazardous waste for not more than 90 days.

B. What Changes Is EPA Proposing to the Conditions for Existing Comparable Fuel?

The proposed rule would restructure the current conditions for comparable fuel (and syngas fuel) to make the regulatory language more readable given that the regulation must accommodate the proposed exclusion for ECF. Consequently, we are redrafting the entire section for clarity. In addition, we are making technical corrections to several provisions of the rule.
10

We regard these language changes as purely technical, and thus will accept comment only on whether the suggested language change expresses the current meaning of the provision. We are not reexamining, reconsidering, or otherwise reopening these provisions for comment.

10
See memorandum from Bob Holloway, USEPA, to Docket ID No. EPA-HQ-RCRA-2005-0017, dated January 10, 2007.

We are, however, proposing to amend several provisions that apply to comparable fuel for the same reasons that we are proposing to apply the amended provisions to ECF. We specifically request comment on whether these clarifications and conforming amendments are appropriate:

• We are proposing to clarify the consequences of failure to satisfy the conditions of the existing comparable fuel exclusion. The material must be managed as hazardous waste from the point of generation. In addition, we are proposing to clarify that excluded fuel that is spilled or leaked and that no longer meets the conditions of the exclusion must be managed as a hazardous waste if it exhibits a characteristic of hazardous waste or if it was derived from a listed hazardous waste when the exclusion was claimed. See proposed § 261.38(d).

• We are proposing to clarify the status of tanks that cease to be operated as comparable fuel storage tanks. The tank system becomes subject to the RCRA hazardous waste facility standards if not cleaned of liquids and accumulated solids within 90 days of ceasing operations as a comparable fuel tank. In addition, we are proposing to clarify that liquids and accumulated solids removed from the tank after the tank ceases to be operated as a comparable fuel product tank must be managed as hazardous waste if they exhibit a characteristic of hazardous waste or if they were derived from a listed hazardous waste when the exclusion was claimed. See proposed § 261.38(b)(13).

• We are proposing to waive the RCRA closure requirements for tank systems that are used only to store hazardous wastes that are subsequently excluded as comparable fuel. See proposed § 261.38(b)(14).

• We are proposing to clarify the regulatory status of boiler residues, including bottom ash and emission control residue. Burning excluded fuel that was derived from a listed hazardous waste does not subject boiler residues to regulation as derived-from hazardous waste. See § 261.38(b)(12).

• We are proposing that the one-time notice by the generator to regulatory officials include an estimate of the average and maximum monthly and annual quantity of waste for which an exclusion would be claimed.
11

See proposed § 261.38(b)(2)(i)(D).

11
Providing an estimate of excluded quantities would help regulatory officials establish inspection and monitoring priorities. This requirement was an oversight when the exclusion was initially promulgated. We required the burner to issue a public notice that included this information (see existing § 261.38(c)(1)(ii)(D)), but we inadvertently did not require the generator who claims the exclusion to provide this information in his notice to regulatory officials.

Part Two: Rationale for the Proposed Rule

I. What Is the Rationale for Excluding Emission-Comparable Fuel From the Definition of Solid Waste?

Emission-comparable fuel (ECF) is a fuel derived from hazardous waste, but which would be excluded from RCRA hazardous waste regulation if it meets prescribed specifications and management conditions. The ECF specifications would be the same as those that currently apply to existing comparable fuel, except the specifications for particular hydrocarbons and oxygenates would not apply. See proposed § 261.38(a)(2).
12

12
Table 1 to § 261.38 provides specifications for 37 hydrocarbons and oxygenates. For ECF, the specifications would not apply for those compounds, except for PAHs and naphthalene, as discussed in Part Two, Section III, of the text. In addition, there would be firing rate restrictions for ECF that contained more than 2% benzene or acrolein.

The exclusion would be based on the rationale that ECF has fuel value, that the hydrocarbon and oxygenate constituents no longer subject to a specification themselves have fuel value, and that emissions from burning ECF in an industrial boiler operating under good combustion conditions are likely not to differ from emissions from burning fossil fuels under those same conditions. Emissions from burning ECF in an industrial boiler operating under good combustion conditions would be comparable to emissions from burning fuel oil in an industrial boiler operating under the same good combustion conditions because operating a boiler under good combustion conditions, evidenced by carbon monoxide (CO) emissions below 100 ppmv (on an hourly rolling average), assures the destruction of organic compounds generally to trace levels, irrespective of the type or concentration of the organic compound in the feed.
13

As

hydrocarbons are oxidized during combustion, eventually (ideally) to carbon dioxide and water, CO is formed just prior to complete oxidation to carbon dioxide. Because CO is difficult to oxidize, it is the rate-limiting step in the oxidation process. Thus, low CO levels indicate good combustion and low levels of organic compounds.

13
This assumes that fuels are fired into the flame zone, thus avoiding total ignition failure. If a waste fuel were inadvertently fired out of the flame zone, the fuel may not even partially combust. If this were to happen, CO levels could be low even though organic emissions could be high. ECF boilers would be required to fire ECF into the primary fuel flame zone. Also see USEPA, “Draft Technical Support

Document for Expansion of the Comparable Fuel Exclusion,” May 2007, Section 5.

EPA has discretion to classify such material as a fuel product, and not as a waste. See generally
Safe Foods and Fertilizer
v.
EPA
, 350 F. 3d 1263, 1269-71 (D.C. Cir. 2004) (secondary materials physically comparable to virgin products which would be used in their place, or which pose similar or otherwise low risks when used in the same manner as the virgin product, need not be considered “discarded” and hence need not be classified as solid wastes). Given that ECF (including the hydrocarbon and oxygenate portion) would have legitimate energy value and that emissions from burning ECF are comparable to fuel oil when burned in an industrial boiler under the good combustion conditions typical of such boilers, classifying such material as a fuel product and not as a waste promotes RCRA's resource recovery goals without creating a risk from burning greater than those posed by fossil fuel. Under these circumstances, EPA can permissibly classify ECF as a non-waste.

The conditional exclusion would be an exclusion only from the RCRA subtitle C regulations, and not from the emergency, remediation and information-gathering sections of the RCRA statute [sections 3007, 3013, and 7003]. This is consistent with the principle already codified for other excluded hazardous secondary materials—that the exclusion is only from the RCRA regulatory provisions, and not from these statutory authorities. See § 261.1(b). We are restating this principle here in the interest of clarity, not to reopen the issue. The legal basis for the distinction of the Agency's authority under these provisions is that they use the broader statutory definition of solid waste (and hazardous waste, as well) and so need not (and should not) be read as being limited by the regulatory definition. See, for example, 50 FR at 627. See also
Connecticut Coastal Fishermen's Assn.
v.
Remington Arms
, 989 F. 2d 1305, 1313-15 (2d Cir. 1993) (EPA may permissibly ascribe different definitions to the term ”solid waste” for regulatory and statutory purposes).

Although ECF could have higher concentrations of particular hydrocarbons and oxygenates than the benchmark fossil fuels—fuel oil and gasoline—that EPA used to establish the specifications in Table 1 to § 261.38, higher levels of hydrocarbons and oxygenates in ECF do not imply that burning ECF for energy recovery constitutes waste management because: (1) Hydrocarbons naturally occur in virgin fuels
14

and oxygenates are a class of compounds that are added to virgin fuels to enhance combustion;
15

(2) the hydrocarbons and oxygenates have a heating value of 10,000 Btu/lb to 18,500 Btu/lb,
16

which is comparable to the range for virgin fuels (e.g., coal and fuel oil); and (3) the hydrocarbons and oxygenates produce emissions comparable to virgin fuels when burned under conditions typical of those under which virgin fuels are burned.

14
We explained in the final comparable fuel rule that it is reasonable to assume that the Table 1 hydrocarbons that we did not detect in fuel oil or gasoline could in fact be present at levels up to the detection limit. See 63 FR at 33791.

15
Examples of fuel oxygenates are: Ethanol; methyl tert-butyl ether (MTBE), tert-amyl methyl ether (TAME); diisopropyl ether (DIPE); ethyl tert-butyl ether (ETBE); tert-amyl alcohol (TAA); and tert-butyl alcohol (TBA). For further discussion, see USEPA, “Draft Technical Support Document for Expansion of the Comparable Fuel Exclusion,” May 2007, Section 3.1.

16
USEPA, “Draft Technical Support Document for Expansion of the Comparable Fuel Exclusion,” May 2007, Section 2.2.

We note, however, that ECF can pose a greater hazard during storage than fuel oil given that ECF can contain higher concentrations of certain hazardous, volatile hydrocarbons and oxygenates. We are consequently proposing to condition the exclusion on certain storage conditions similar to those applicable to commercial products and commodities analogous to ECF, namely fuel oil and other commercial organic liquids. See discussion below in Part Two, Section IV.

In addition, we are proposing to condition the exclusion on requirements for the design and operation of the ECF burner to ensure that ECF is burned under the good combustion conditions typical of most fossil fuel boilers. See discussion below in Part Two, Section II. These conditions should ensure that emissions from burning ECF remain comparable to emissions from burning fossil fuels.

A. Why Would the Specifications Be Waived Only for Hydrocarbons and Oxygenates?

We are proposing not to apply the specifications for certain hydrocarbons and oxygenates, but are proposing to retain the specifications for metals and the other categories of organic compounds for which specifications are provided under § 261.38. We would not apply the specifications for these hydrocarbons
17

because: (1) It is reasonable to assume that these compounds may be present in fossil fuels (see 63 FR at 33791); and (2) when they are burned under the good combustion conditions typical for fossil fuel-fired boilers, emissions from burning these compounds would be comparable to emissions from burning fuel oil.

17
Please note, however, that we are proposing to retain the specifications for certain hydrocarbons: PAHs (polycyclic aromatic hydrocarbons) and naphthalene. See discussion in the text in Part Two, Section III.

We also would not apply the specifications for the listed oxygenates because they are a class of organic compounds that are added to fuels to enhance combustion.
18

These compounds would burn cleanly under the good combustion conditions typical of a fuel oil-fired industrial boiler and would generate only trace or comparable levels of emissions.

18
We acknowledge that oxygenates are added to fuels burned in internal combustion engines rather than fuels burned in industrial boilers. However, oxygenates burn cleanly—they do not contain halogens, sulfur, or nitrogen that would result in emissions of halogen acids and sulfur and nitrogen oxides.

It is appropriate to retain the specifications for metals since they do not contribute energy and are not destroyed during the combustion process. Given that the metal specifications in Table 1 to § 261.38 reflect levels that can be present in fuel oil, excess, noncontributing metals are “along for the ride,” suggesting discarding. Moreover, metals emissions would necessarily be higher than emissions from fuel oil if the metals specifications do not apply because oil-fired boilers typically lack optimized particulate control due to low metal content of commercially available fuel oils.

Also, it is appropriate to retain the specifications for the other categories of organic compounds listed under Table 1 to § 261.38—sulfonated organics, nitrogenated organics, and halogenated organic compounds. These organic compounds, for the most part, are not likely to be found in the benchmark fuels—fuel oil and gasoline—we used to establish the specifications. And, unlike oxygenates, these organic compounds are not within a class of compounds that are added to fossil fuels to enhance combustion. These hazardous compounds also would appear to be along for the ride when present at concentrations higher than benchmark

fuels, and consequently their destruction via combustion can be viewed as waste management.

B. Do Available Data and Information Support a Comparable Emissions Finding?

We investigated whether emissions from burning ECF in an industrial boiler operating under prescribed good combustion conditions would be comparable to emissions from burning fuel oil in an industrial boiler operating under good combustion conditions. We evaluated organic emissions data from watertube steam boilers (other than stoker-fired boilers) burning hazardous waste and compared those emissions against emissions from oil-fired industrial boilers. In addition, we conducted two qualitative analyses of the risk that ECF emissions may pose: (1) Evaluation of RCRA risk assessments for watertube steam boilers burning hazardous waste to determine if organic emissions had been found to pose a hazard to human health and the environment; and (2) a limited comparative risk assessment for dioxin/furan emissions.

As discussed below, we believe that available data and information indicate that emissions from burning ECF under the proposed, prescribed conditions would be comparable to emissions from an oil-fired industrial watertube steam boiler operating under good combustion conditions.

1. Evaluation of Organic Emissions Data for Hazardous Waste Boilers

In the absence of emissions data from boilers burning ECF, we evaluated organic emissions data from watertube steam boilers burning hazardous waste and compared those emissions against emissions from oil-fired industrial boilers. Using hazardous waste boiler emissions as a surrogate for ECF boiler emissions is a reasonable worst-case because the exclusion would be conditioned on the ECF boiler operating under conditions relating to assuring good combustion conditions that are at least as stringent as those required of boilers burning hazardous waste.
19

19
See discussion in Part Two, Section II, of the text describing the ECF boiler conditions. The CO controls for ECF boilers plus the requirement to fire ECF into the primary fuel flame zone are equivalent to the controls on organic emissions for hazardous waste boilers—CO controls and compliance with the 99.99% destruction and removal efficiency (DRE) standard. The other ECF boiler controls are more restrictive than controls that apply to hazardous waste boilers, but are appropriate to help assure that an ECF boiler operates under good combustion conditions given that ECF would be burned under a conditional exclusion absent a RCRA permit and the regulatory oversight typical for a RCRA hazardous waste combustor, and absent the extensive operating limits (e.g., combustion chamber temperature, maximum load) that are established subsequent to emissions testing to demonstrate compliance with a destruction and removal efficiency (DRE) standard.

We obtained organic emissions data for 26 hazardous waste watertube steam boilers which data were generated during risk-burn testing required under RCRA omnibus authority codified at § 270.32(b)(2). EPA requires this testing as necessary on a site-specific basis to ensure that emissions are protective of human health and the environment. We have data for 28 test conditions for the 26 boilers that provide 175 detected measurements of organic compounds, where a measurement is a three-run set.
20

We also have data for hazardous organic compounds emitted from oil-fired industrial boilers. Those data were compiled in support of the NESHAP for Industrial, Commercial, and Institutional Boilers and Process Heaters promulgated under Part 63, Subpart DDDDD. See 69 FR 55218 (Sept. 13, 2004). We use oil-fired industrial boiler emissions data for comparison because fuel oil is the closest analogous fuel to ECF, and ECF could be burned only in industrial or utility boilers. See discussion below in Section II.B.1.

20
A test condition is normally comprised of three test runs conducted under identical (controllable) operating conditions.

We have emissions data for both hazardous waste boilers and oil-fired industrial boilers for 26 hazardous organic compounds. We also have hazardous waste boiler emissions data for another 33 hazardous organic compounds for which we do not have oil-fired boiler emissions data for comparison. We discuss our investigation of these data below.

a. Hazardous Organic Compounds for Which We Have Both Hazardous Waste Boiler and Fuel Oil Boiler Emissions Data
. We have both hazardous waste boiler and fuel-oil boiler emissions data for 26 hazardous organic compounds. The great majority of the hazardous waste boiler test condition averages for these compounds (150, or greater than 85%) were unequivocally comparable to fuel oil emissions—the hazardous waste emissions were below the oil emissions 95th percentile level. There were 24 test condition averages, however, that exceeded the oil emissions 95th percentile level for 10 compounds.
21

Nonetheless, we do not believe that these exceedances indicate that ECF emissions would be higher than oil-fired boiler emissions, as discussed below.

21
Please note that we have reanalyzed the oil-fired boiler emissions data to identify the 95th percentile benchmarks based on test condition averages, rather than test runs, based on comments submitted by one of the peer reviewers. As discussed in Part Two, Section VII, although the reanalysis resulted in several additional exceedances of the oil emissions benchmarks, our conclusion remains unchanged. It is reasonable to conclude that ECF emissions will be either generally comparable to oil emissions or at
de minimis
levels.

For 12 of the 24 exceedances, laboratory contamination of the sample was known or suspected. Specifically, for nine exceedances—six for dichloromethane, two for benzene, and one for toluene—the constituent being measured was found in the blank, while there were three additional exceedances for dichloromethane, a common lab contaminant that is frequently found in laboratory samples and in the environment. For one of these test conditions, the report indicated that dichloromethane is a common laboratory contaminant, implying that the data may be suspect. For the other two test conditions, laboratory contamination was not discussed in the test reports. Even if laboratory contamination were not an issue for these two tests, however, we note that these hazardous waste boilers were not operating under the conditions that are proposed for an ECF boiler. Both boilers were burning waste fuels with a heating value below the 8,000 Btu/lb minimum heating value that is proposed for ECF. In addition, it is unclear if one boiler was burning vent gas or natural gas as the primary fuel. ECF must be burned with at least 50% primary fuel that is fossil fuel. Operating under conditions less stringent than proposed for ECF boilers could result in higher emissions of organic compounds.

For seven exceedances, hazardous waste boiler emissions were at trace levels
22

—there was a
de minimis
increase in emissions. Test condition averages were below 8 μg/dscm for the exceedances for anthracene, benzo[a]pyrene, ethylbenzene, fluorine, 2-methlynaphthalene, and phenanthrene.

22
Emissions of 8 μg/dscm for high molecular weight compounds such as these are equivalent to approximately 0.005 ppmv expressed as propane equivalents. Thus, these are
de minimis
concentrations considering that the hydrocarbon emission limit for boilers burning hazardous waste is 10 ppmv, expressed as propane equivalents. See § 63.1217(a)(5)(ii).

In addition, an exceedance for acetaldehyde was at an emissions level of 100 μg/dscm, while oil emission levels for acetaldehyde are virtually comparable at 70 μg/dscm. However, the hazardous waste boiler emissions for acetaldehyde were well below the 95th percentile emissions for natural gas boilers, 635 μg/dscm. This is relevant because ECF may be burned with natural gas as the primary fuel. Further,

we note that the hazardous waste boiler was operating under conditions less stringent than proposed for ECF boilers—it was burning only 20% natural gas as the primary fuel, while it is proposed that ECF boilers fire at least 50% primary fuel. Thus, acetaldehyde emissions may be higher than they would have been if the boiler had the hot, stable flame that burning 50% natural gas (or fuel oil) would provide.

Finally, there were four exceedances for benzene that we nonetheless believe are comparable to fuel oil emissions. Three of the exceedances were below the highest fuel oil emission test run level of 200 μg/dscm, while the fourth exceedance was at a level of 260 μg/dscm, just somewhat higher. More importantly, for all four exceedances, the hazardous waste boiler was not operating under the conditions proposed for an ECF boiler. For all four exceedances, the hazardous waste fuel had a heating value below 2,000 Btu/lb compared to 8,000 Btu/lb that is proposed for ECF. And, for one of the exceedances, the hazardous waste fuel had a viscosity of 165 cSt, while the maximum viscosity for ECF would be 50 cSt. To reiterate, operating under conditions less stringent than proposed for ECF boilers could result in higher emissions of organic compounds.

Notwithstanding this analysis of available emissions data, we acknowledge that, when ECF with higher concentrations of certain hydrocarbons and oxygenates than fuel oil is burned even under good combustion conditions, emissions of hazardous organics may be somewhat higher than those from burning fossil fuel. This is because combustion is generally a percent-reduction process. Thus, even though good combustion conditions may ensure a very high destruction efficiency (e.g., 99.9999% reduction), emission concentrations may nonetheless increase as the feedrate of an organic compound increases. We believe, however, that these increases would be
de minimis
because operating under the good combustion conditions proposed for ECF boilers ensures that emissions of hazardous organic compounds would generally be at trace levels, and, as discussed below, protective of human health and the environment.
23

23
Please note that a peer reviewer questioned whether ECF emissions could, in fact, be expected to be comparable to oil-fired boiler emissions given the unlimited concentrations of the listed hazardous compounds (i.e., benzene, toluene, and the oxygenates) that may be present in ECF. We respond to this comment in Part Two, Section VII of the preamble.

b. Compounds for Which We Only Have Hazardous Waste Boiler Emissions Data
. We have hazardous waste boiler emissions data for 33 hazardous organic compounds for which we do not have oil-fired boiler emissions data for comparison. Average hazardous waste boiler emissions for each of these compounds are at trace levels—below 11 μg/dscm
24

—except for bis(2-ethylhexyl)phthalate and chloroform.

24
As discussed in footnote 22, emissions at this low concentration are in the
de minimis
range.

We have bis(2-ethylhexyl)phthalate emissions data for 15 test conditions (generally comprised of three runs) representing 15 different boilers. Test condition average emissions ranged from 0.34 μg/dscm to 600 μg/dscm for the boilers, with an average of 69 μg/dscm. Although the highest test condition average—600 μg/dscm—appeared to be an outlier given that the second highest average was 130 μg/dscm and 12 test conditions were below 42 μg/dscm, we determined that it is not a statistical outlier.
25

Nonetheless, we note that: (1) The boiler with the highest emissions—600 μg/dscm—was not operating under the conditions that are proposed for an ECF boiler (which could result in higher emissions)—the primary fuel firing rate was approximately 30% rather than a minimum of 50%, and boiler load was approximately 30% rather than a minimum of 40%; and (2) bis(2-ethylhexyl)phthalate is known to be a common lab contaminant, and thus the reported emissions levels may be suspect.

25
USEPA, “Draft Technical Support Document for Expansion of the Comparable Fuel Exclusion,” May 2007, Appendix C.

For chloroform, we have emissions data for 9 test conditions (generally comprised of three runs) representing 9 different boilers. Test condition average emissions ranged from 0.28 μg/dscm to 270 μg/dscm for the boilers, with an average of 45 μg/dscm. Although the highest test condition average—270 μg/dscm—appeared to be an outlier given that the second highest average was 85 μg/dscm and the remaining test conditions did not exceed 16 μg/dscm, we determined that it is not a statistical outlier. We note, however, that the boiler with the highest emissions—270 μg/dscm—was not operating under the conditions that are proposed for an ECF boiler—it burned a waste fuel with a heating value below 8,000 Btu/lb and it is not clear whether the boiler burned process vent gas or natural gas as primary fuel.

2. Evaluation of RCRA Risk Assessments

In addition to the analysis of emission concentrations discussed above, we reviewed the RCRA risk assessments
26

that had been completed by June 2006 for hazardous waste watertube steam boilers other than stoker-fired boilers to determine if organic emissions under the good combustion conditions required by the standards under Part 266, Subpart H, may result in unacceptable risk to human health and the environment. We determined that such risk assessments had been conducted at 13 facilities and decisions on whether omnibus/additional permit conditions are needed to ensure emissions are protective have been made for nine of those facilities. A decision to include an omnibus permit condition to address organic emissions has been made for only two of the nine facilities, however.

26
See § 270.32(b)(2).

The first facility operated several boilers equipped with a common electrostatic precipitator. Risk-based dioxin emission limitations and associated testing and temperature monitoring requirements were established in the permit based upon a finding that dioxin/furan emissions during an isolated test event exceeded risk levels of concern. During that test event, artificial chlorine spiking into the waste feed was conducted. During subsequent testing under the permit terms, chlorine spiking did not take place and compliance with the risk-based dioxin/furan emission limitations was demonstrated. Electrostatic precipitator operating temperatures during the subsequent tests ranged from 396 °F to 418 °F. We note, however, that the chlorine specification proposed for ECF would prohibit chlorine concentrations from approaching the levels present during the instances of chlorine spiking at this facility. In addition, we also note that today's proposal would require that ECF boilers (other than coal-fired boilers) equipped with an ESP or FF maintain a gas temperature below 400 °F as a condition of the exclusion. See discussion in Section II below.

For the second facility where omnibus permit conditions were imposed, there was no finding of excess risk associated with any organic constituents. Rather, the omnibus permit conditions serve as a trigger for a reassessment of risk if emissions levels higher than those considered in the initial risk assessment were measured.

This analysis confirms our view that organic emissions from hazardous waste

boilers operating under good combustion conditions required under §§ 266.104 and 63.1217 are generally protective. It also confirms our view that organic emissions from ECF boilers operating under the good combustion conditions discussed in Section II below should be protective.

3. Comparative Risk Assessment for Dioxin/Furan

Finally, we also conducted an abbreviated comparative risk assessment for dioxin/furan emissions from boilers burning hazardous waste and that meet the design conditions for an ECF boiler discussed below in Section II—a watertube steam boiler that is not stoker-fired. The abbreviated evaluation used one component of the comparative risk evaluation used to support the Phase II hazardous waste combustor MACT for boilers
27

—the Margin of Exposure (MOE) analysis.
28

The emission-adjusted MOE analysis uses the risk “safety margins” (i.e., modeled MOEs) determined from the MACT Phase I comprehensive risk assessment for hazardous waste incinerators
29

to determine whether, considering emissions alone, risks for a second universe, here, the ECF boilers, could rise to a level of concern.
30

Smaller MOEs correspond to a greater potential for risk beyond the level of concern (i.e., 1E-05 lifetime cancer risk). In this analysis, we: (1) Revised the dioxin/furan emissions data base for Phase II hazardous waste boilers to establish a data base of boilers that meet the ECF boiler design conditions (i.e., by eliminating boilers other than watertube steam boilers that are not stoker-fired) and by adding dioxin/furan emissions data obtained during the evaluation of risk burns for hazardous waste boilers, as discussed above; (2) calculated point estimates and confidence intervals for the revised emissions data base; (3) combined the Phase I incinerator data base with the revised (i.e., ECF) boiler data base and conducted tests for common generalized percentiles; and (4) adjusted the MOE, if appropriate.

31
The analysis indicates that the emissions-adjusted MOEs representing the ECF boilers are higher than the MOEs for the Phase I incinerators. This suggests a lower potential for risk for the ECF boilers compared to hazardous waste incinerators. This means that, within the limitations of the analyses, dioxin/furan emissions from ECF boilers pose no greater hazard than the emissions from hazardous waste incinerators, and therefore, should remain within levels that are protective.

27
See 70 FR at 59536-37 (October 12, 2005).

28
USEPA, “Assessment of the Potential Costs, Benefits, & Other Impacts of the Hazardous Waste Combustion MACT Final Rule Standards,” September 2005, Chapter 6.

29
RTI International, “Inferential Risk Analysis in Support of Standards for Hazardous Air Pollutant Emissions from Hazardous Waste Combustion,” June 2005, Section 1.

30
It must be emphasized that emission-adjusted MOEs should not be construed as predictions of the level of risk. Instead, they are only intended to provide an indication of whether risks could exceed a level of concern based on simplifying assumptions and as such, are subject to some level of uncertainty.

31
See USEPA, USEPA, “Draft Technical Support Document for Expansion of the Comparable Fuel Exclusion,” May 2007, Section 5.3.4.

Based on this information—comparison of emissions concentrations from hazardous waste boilers and oil-fired boilers; evaluation of omnibus risk assessments; and evaluation of dioxin/furan risk—we conclude that emissions from burning ECF in a boiler under the conditions proposed today would be comparable to fuel oil emissions and would be generally protective of human health and the environment. We specifically request additional data and comment on our analyses and conclusions.

II. What Conditions Would Apply to Burners of Emission-Comparable Fuel?

The ECF exclusion proposed today would be conditioned on burning ECF under conditions typical of a fuel oil-fired industrial boiler operating under good combustion conditions. The ECF conditions would ensure that the boiler maintains a hot, stable flame, and that ECF is properly atomized and fired into that flame. In addition, post-combustion conditions would minimize the potential for dioxin/furan formation by controlling the combustion gas temperature at the inlet to a dry particulate matter control device for boilers so-equipped. Accordingly, we propose the following conditions: (1) The burner must be a watertube steam boiler other than a stoker-fired boiler; (2) carbon monoxide (CO) must be monitored continuously, must be linked to an automatic ECF feed cutoff system, and must not exceed 100 ppmv on an hourly rolling average (corrected to 7% oxygen); (3) the boiler must fire at least 50% primary fuel on a heat input or volume basis, whichever results in a higher volume of primary fuel, and the primary fuel must be fossil fuel or tall oil with a heating value not less than 8,000 Btu/lb; (4) the boiler load must be 40% or greater; (5) the ECF must have an as-fired heating value of 8,000 Btu/lb or greater; (6) ECF must be fired into the primary fuel flame zone; (7) the ECF firing system must provide proper atomization; and (8) if the boiler is equipped with an electrostatic precipitator (ESP) or fabric filter (FF) and does not fire coal as the primary fuel, the combustion gas temperature at the inlet to the ESP or FF must be continuously monitored, must be linked to the automatic ECF feed cutoff system, and must not exceed 400 °F on an hourly rolling average. These conditions are consistent with oil-fired industrial boiler design and operating conditions that ensure good combustion (and post-combustion control of dioxin/furan) and ensure that emissions from burning ECF are comparable to fuel oil emissions.
32

In addition, as discussed in the previous section, such emissions would be at levels which are protective of human health and the environment.

32
Given that burning ECF under the proposed conditions will destroy toxic organic compounds in the ECF generally to trace levels, we are proposing that burning excluded fuel that was derived from a hazardous waste listed under §§ 261.31-261.33 does not subject boiler residues, including bottom ash and emission control residues, to regulation as derived-from hazardous waste. See proposed § 261.38(b)(12).

The boiler design and operating conditions that ensure a hot, stable flame and good combustion of ECF (i.e., all of the conditions, except the condition to minimize post-combustion formation of dioxin/furan by limiting the gas temperature at the inlet to the ESP or FF) derive from extensive testing that EPA conducted in the mid-1980's to identify design and operating parameters that affect the combustion of hazardous organic compounds in waste fuels fired as supplementary fuel in boilers. See 52 FR at 16995-96 (May 6, 1987). EPA used the results of that testing to identify design and operating conditions that would ensure that waste fuel is properly atomized and fired into a hot, stable flame to ensure destruction of hazardous organics in the waste fuel to trace levels and to minimize formation of products of incomplete combustion (PICs) to levels that would not pose a hazard to human health or the environment.

Those operating conditions also reflect typical operations for an oil-fired industrial boiler operating under good combustion conditions: (1) As discussed below, CO levels below 100 ppmv are typically achieved by oil-fired industrial boilers; (2) the oil fuel provides a hot, stable flame; and (3) boilers generally operate at loads greater than 40% and can experience poor combustion conditions at lower loads. The design conditions—the boiler must be a watertube steam boiler that is not stoker-fired—also reflect industrial

boiler designs that help ensure optimum combustion efficiency. See discussion below in Section B.1.

A. Why Isn't a DRE Performance Test a Critical Requirement To Ensure Good Combustion Conditions?

EPA concluded from the boiler testing discussed above that: (1) Boilers cofiring hazardous waste fuels with fossil fuels where the hazardous waste provides less than 50 percent of the boiler's fuel requirements can achieve 99.99 percent destruction and removal efficiency (DRE) of POHCs (principal organic hazardous constituents) under a wide range of operating conditions (e.g., load changes, waste feed rate changes, excess air rate changes); (2) when boilers are operated at high combustion efficiency, as evidenced by flue gas carbon monoxide (CO) levels of less than 100 ppmv, DRE exceeds 99.99 percent; (3) boilers clearly operating under poor combustion conditions, as evidenced, for example, by smoke emissions, still achieved 99.99 percent DRE: (4) emissions of PICs appeared generally to increase as combustion efficiency decreased as evidenced by increased flue gas CO levels; and (5) emission of total unburned hydrocarbons (i.e., quantified Part 261, Appendix VIII pollutants, as well as unburned POHCs and other unburned organic compounds) may increase as combustion efficiency decreases as evidenced by an increase in flue gas CO levels. See 52 FR at 16995.

These results confirm that a 99.99% DRE regulatory requirement (coupled with compliance with limits on operating conditions established during the DRE performance test) has limited utility for ensuring that a combustor operates under the good combustion conditions necessary to destroy both hazardous organics in the fuel feed and PICs to levels that are protective of human health.
33

EPA has explained, however, why a limit on carbon monoxide emissions (i.e., 100 ppmv, hourly rolling average) is a conservative indicator of good combustion conditions for boilers (and other combustors) that will result in destruction of both POHCs and PICs. See 52 FR at 16998; 70 FR at 59461-463. Of the four combustion failure modes that EPA has identified—total ignition failure, partial ignition failure, combustion air failure, and rapid quench failure—only a total ignition failure could result in low CO and poor combustion of POHCs and PICs.
34

Total ignition failure could potentially occur in a boiler if the fuel firing gun inadvertently directed the fuel to a location in the combustion chamber away from the flame zone—i.e., if the fuel were not fired into the flame zone. The other combustion failure modes result in high CO and potentially high unburned organics:
35

partial ignition failure; combustion air failure; and rapid quench failure. Thus, it is important to ensure that waste fuels are fired into the flame zone of a boiler when relying on CO emission levels to ensure good combustion conditions (and that 99.99% DRE is achieved), as proposed for ECF boilers.

33
We note that, for this reason, hazardous waste boilers are currently exempt from the requirement to demonstrate 99.99% DRE if the boiler complies with specific design and operating conditions, including the principal organic emission control requirement of continuously monitoring CO and compliance with a limit of 100 ppmv. See § 266.110. We note further that the ECF boiler conditions proposed today are at least as stringent as the conditions provided by § 266.110.

34
See USEPA, USEPA, “Draft Technical Support Document for Expansion of the Comparable Fuel Exclusion,” May 2007, Appendix A.

35
Because CO is more thermally stable than other intermediate combustion products, high CO emissions may or may not be indicative of high PIC emissions. If CO is low, however, combustion has progressed to the point that PIC emissions will be low (assuming total ignition failure is avoided). Thus, CO is considered a conservative indicator of good combustion. See 52 FR at 16998.

B. What Is the Rationale for the Proposed Burner Conditions?

From the discussion above, it could be argued that the only controls needed to ensure good combustion conditions and destruction of hazardous organics in ECF would be continuous monitoring of carbon monoxide and a requirement to fire ECF into the flame zone to avoid total ignition failure. Notwithstanding this view, we believe it is appropriate to apply additional controls to help ensure that an ECF boiler operates under the good combustion conditions typical of an oil-fired industrial boiler given that ECF would be burned under a conditional exclusion absent a RCRA permit and the regulatory oversight typical for a RCRA hazardous waste combustor. The proposed conditions would help ensure good combustion conditions by requiring that ECF has substantial heating value and that it is fired into a hot, stable flame. There are many industrial boilers that meet the design criteria (i.e., watertube steam boiler that is not stoker-fired) and the operating conditions generally reflect standard operating practice. The proposed conditions consequently are analogous to conditions under which fuel oil, the commercial product for which ECF substitutes, are burned. Furthermore, more than 90% of the candidate waste fuel streams identified by generators had heating values greater than 8,000 Btu/lb.
36

36
Letter from American Chemistry Council (Carter Lee Kelly, Leader, Waste Issues Team, and Robert A. Elam, Director, Regulatory Affairs, Waste Issues Team) to Robert Springer and Matt Hale, USEPA, dated November 24, 2003.

The rationale for each of the proposed burner conditions is discussed below. We specifically request comment on each of these proposed conditions.

1. ECF Must Be Burned in a Watertube Steam Industrial or Utility Boiler That Is Not Stoker-Fired

A condition of the proposed exclusion would require the ECF burner to be a watertube steam boiler that does not fire fuels using a stoker or spreader-stoker feed system.
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ECF also must be burned in a boiler rather than in an industrial furnace, such as a cement kiln, because the Agency conducted nonsteady-state emissions tests (as part of the boiler testing program discussed above) to identify the parameters that affect combustion efficiency only for boilers. Industrial furnaces have a primary purpose other than burning fuels most efficiently and we have not determined the operating conditions that would ensure good combustion conditions absent the regulatory oversight provided by the RCRA hazardous waste permit program.

37
Stoker-fired boilers are designed to burn solid fuels (including coal, wood, municipal wastes, etc.) on a bed. Stokers are mechanical or pneumatic devices that feed solid fuels onto a grate at the bottom of the furnace and remove the ash residue after combustion. See USEPA, USEPA, “Draft Technical Support Document for Expansion of the Comparable Fuel Exclusion,” May 2007, Section 3.3.2.

The boiler must be a watertube, nonstoker boiler because there is a greater potential for poor distribution of combustion gases and localized cold spots in firetube and stoker boilers that can result in poor combustion conditions. In particular, stoker and spreader-stoker boilers generally burn solid fuels with a relatively large particle size on a bed, thus making even distribution of combustion air difficult. See 56 FR at 7148.

The boiler must be a steam boiler rather than a process heater because process heaters can have a primary purpose other than to burn fuels under optimum combustion conditions. An example is a process heater that quenches combustion gases to reduce gas temperatures to avoid overheating a process fluid. Such operating conditions could adversely affect combustion efficiency by interrupting the complete combustion of organic compounds.

Finally, the boiler must be an industrial or utility boiler as currently

required under the comparable fuel exclusion. See proposed § 261.38(c)(2)(i). This would ensure that ECF is burned in boilers that are capable of handling this type of fuel (e.g., rather than boilers at schools, apartments, or hospitals) and that would be subject to Federal, state, or local air emission requirements.

We request comment on whether there are other types of combustors (e.g., thermal oxidizer) that may be able to burn ECF under the good combustion conditions comparable to an industrial watertube steam boiler (that is not of stoker design). Any suggestions for other types of combustors must include supporting information in order for the Agency to be able to consider it for final action.

2. CO Monitoring

A condition of the proposed exclusion would require that combustion gas CO be monitored continuously, that the CO recordings be linked to an automatic ECF feed cutoff system, and that CO emissions not exceed 100 ppmv on an hourly rolling average (corrected to 7% oxygen). As discussed above, low CO emissions, coupled with firing ECF in the primary fuel flame zone, are the primary controls for ensuring that the boiler is operating under good combustion conditions.

EPA has used continuous CO monitoring as an indicator of good combustion for various types of combustors, including boilers that burn hazardous waste and boilers that do not burn hazardous waste. See 70 FR at 59463-64 for a discussion of using CO to control organic HAP under the NESHAP for hazardous waste boilers,
38

and 68 FR at 1671 for a similar discussion in the context of the NESHAP for boilers that do not burn hazardous waste. We note that the NESHAP for boilers that do not burn hazardous waste (i.e., Industrial Boiler NESHAP) requires continuous CO monitoring only for new solid, liquid, or gas boilers with a capacity greater than 100 MM Btu/hr. The CO limit is 400 ppmv corrected to 3% oxygen for oil and gas boilers and 400 ppmv corrected to 7% oxygen for solid fuel boilers, and is based on a 30-day average. Boilers with a capacity in the range of 10 MM Btu/hr to 100 MM Btu/hr comply with the CO limit based on a 3-run average during periodic performance testing. See Table 1 to Subpart DDDDD, Part 63. EPA did not establish a CO limit for existing boilers that do not burn hazardous waste because: (1) CO monitoring was not floor control given that inadequate information was available to conclude that 6% of the sources were equipped with CO monitors or that 6% of the sources were subject to state standards for CO monitoring; and (2) CO monitoring did not appear to be cost-effective as a beyond-the-floor control technique. For new sources where MACT floor is based on the performance of the single best performing source within a category or subcategory, EPA established CO monitoring requirements based on the most stringent state standards for CO monitoring that applied to all large boilers (i.e., greater than 10 MM Btu/hr) in a subcategory (i.e., solid fuel, liquid, and gas boilers) and to all fuel types burned by boilers within the subcategory (e.g., for solid fuel boilers, coal, wood, and other biomass).
39

38
The NESHAP for hazardous waste boilers allow sources to continuously monitor total hydrocarbons and comply with a limit of 10 ppmv in lieu of continuously monitoring CO and complying with a limit of 100 ppmv. See §§ 63.1216(a)(5) and 63.1217(a)(5). We are not proposing a total hydrocarbon alternative for ECF boilers, however, because very few, if any, hazardous waste boilers elect that alternative given the complexity of maintaining a continuous hydrocarbon monitor. In addition, boilers that are designed to rapidly quench the combustion gas temperature and thus cannot achieve CO levels below 100 ppmv have no choice other than to monitor hydrocarbons if they burn hazardous waste fuels. But, these boilers may not be appropriate candidates for burning ECF even if they achieve hydrocarbon levels below 10 ppmv absent the regulatory oversight of a RCRA or Title V permit given that they are not designed to achieve optimum combustion efficiency. Nonetheless, we request comment on whether the rule, if finalized, should allow ECF boilers the option of continuously monitoring hydrocarbons and complying with a limit of 10 ppmv as an alternative to CO monitoring.

39
See 68 FR at 1673 and the memorandum from Jim Eddinger, EPA, to Docket No. OAR-2002-0058 entitled, “Revised MACT Floor Analysis for the Industrial, Commercial, and Institutional Boilers and Process Heaters National Emission Standards for Hazardous Air Pollutants Based on Public Comments,” dated February 2004, pp. 18-19.

Notwithstanding the 400 ppmv CO limit (based on a 30-day average or periodic performance testing
40

) applicable to new industrial boilers that do not burn hazardous waste, a 100 ppmv limit (based on an hourly rolling average) is appropriate for ECF burners because: (1) The limited CO data in the Industrial Boiler NESHAP data base indicate that oil-fired boilers, the boiler subcategory most analogous to a boiler burning ECF, are achieving CO levels below 100 ppmv;
41

(2) hazardous waste fuels that are proposed to be excluded as ECF are currently burned in boilers subject to a 100 ppmv (hourly rolling average) CO standard under RCRA § 266.104, also indicating that a CO limit of 100 ppmv is readily achievable; and (3) a tighter CO limit for ECF than the CO limit that applies to industrial boilers burning fossil fuels and nonhazardous waste fuels is appropriate given the greater potential for ECF emissions to pose a hazard to human health and the environment (i.e., it is reasonable and appropriate to tailor the management controls that apply to the most analogous product, fuel oil, to address the greater hazards posed by potentially high concentrations of hazardous organic compounds in ECF).
42

40
The 30-day averaging period for the Industrial Boiler NESHAP was adopted because boilers burning biomass under certain conditions (e.g., wet wood after a rain event) could not achieve the CO limit over a shorter averaging period. This situation is not relevant here. ECF boilers that burn fuel oil or natural gas as primary fuel can readily achieve a 100 ppmv CO limit over an hourly rolling average.

41
See USEPA, USEPA, “Draft Technical Support Document for Expansion of the Comparable Fuel Exclusion,” May 2007, Section 3.4. Also, we note that EPA adopted the 400 ppmv CO limit for boilers that do not burn hazardous waste to accommodate the higher CO levels that can result from burning solids, particularly wet biomass after rain events. That scenario would not be applicable to a boiler burning ECF. ECF boilers can readily achieve CO levels below 100 ppmv.

42
The hazardous waste boiler emissions data we analyzed as a surrogate for ECF emissions data to determine if emission concentrations were comparable to fuel oil emissions were derived from hazardous waste boilers operating under a CO limit of 100 ppmv. If those boilers operated at higher CO levels and thus at lower combustion efficiency, emissions of toxic organic compounds may have been higher.

We similarly do not believe that periodic rather than continuous CO monitoring would be appropriate for ECF boilers, even though periodic CO monitoring is allowed under the Industrial Boiler NESHAP to boilers in the size range of 10 MM Btu/hr to 100 MM Btu/hr. As discussed above, low CO emissions, combined with the requirement to fire ECF into the primary fuel flame zone, is the principal indicator of good combustion conditions. Periodic CO monitoring would ensure good combustion conditions only periodically—combustion conditions could deteriorate an hour, day, or week after the periodic performance test. Given the potential hazards that burning ECF under poor combustion conditions can pose compared to fossil fuels and nonhazardous waste fuels, and given the variability in combustion characteristics that ECF may have over time relative to the primary fuel, it is reasonable to condition the exclusion on continuous CO monitoring.
43

Nonetheless, we specifically request comment on whether periodic rather than continuous

CO monitoring should be allowed for ECF boilers in the size range of 10 MM Btu/hr to 100 MM Btu/hr, consistent with the Industrial Boiler NESHAP CO monitoring provisions for new boilers. Commenters must explain and provide supporting information why periodic monitoring is sufficient, including how the owner or operator would ensure that the boiler is operating under “good combustion conditions” during those times that the boiler is not being monitored for CO in order for the Agency to be able to consider it for final action.

43
The Industrial Boiler NESHAP requires CO monitoring, albeit periodic monitoring, for all new boilers in the size range of 10 MM Btu/hr to 100 MM Btu/hr. The proposed continuous CO monitoring conditions for ECF boilers, irrespective of size, would apply only to those boilers that elect to burn ECF.

Finally, we propose to specify that the CO monitor must be linked to an automatic ECF feed cutoff system to ensure that ECF is fired only when the boiler is operating under good combustion conditions—when CO levels are below 100 ppmv on an hourly rolling average. Linking the CO monitor to an automatic ECF feed cutoff system is appropriate given that emissions may be neither comparable to fuel oil nor protective if the boiler is not operating under good combustion conditions. An automatic feed cutoff system does not appear to be cost-prohibitive and would help assure effective combustion. We propose to adopt the provisions for automatic feed cutoff systems that apply to boilers that burn hazardous waste—§ 63.1206(c)(3)—and for the same reasons. See USEPA, “Technical Support Document for HWC MACT Standards, Volume IV: Compliance with the HWC MACT Standards,” July 1999, Chapter 11.

3. The Boiler Must Fire at Least 50% Primary Fuel

A condition of the proposed exclusion would require an ECF boiler to fire at least 50% primary fuel on a heat input or volume basis, whichever results in a higher volume of primary fuel, and the primary fuel must be fossil fuel or tall oil with a heating value not less than 8,000 Btu/lb. These conditions would ensure that a hot, stable flame is provided to help ensure optimum combustion conditions. Although a primary fuel firing rate of 50% is at the lower end of the range of reasonable values—50% to 75% primary fuel—that could have been selected, we believe it is a reasonable condition because it would ensure that the boiler is burning primarily fossil fuel (or equivalent) and so ensures a hot, stable flame.
44

We also note that this condition would be consistent with the primary fuel requirement for hazardous waste boilers under § 266.110 that elect to waive the DRE performance standard under operating conditions that ensure optimum combustion efficiency.

44
ECF could be cofired with other fuels, including waste fuels, that may not have combustion characteristics comparable to fuel oil, natural gas, or ECF. Thus, absent a condition that at least 50% of the fuel must have a heating value of 8,000 Btu/lb or greater, a hot, stable flame into which ECF would be fired could not be assured.

The primary fuel would be required to have a minimum heating value of 8,000 Btu/lb to reflect the low end of the range of heating values for fossil fuels normally fired in industrial boilers. Most coal-fired industrial boilers burn either subbituminous coal (with heating values ranging from 8,300-11,500 Btu/lb) or bituminous coal (with heating values ranging from 10,500 to 14,000 Btu/lb). Lignite, a low-rank coal that typically has a heating value below 8,000 Btu/lb, is not commonly burned in industrial boilers.

Although we believe that the primary fuel would generally be fossil fuel—oil, natural gas, or coal (i.e., pulverized coal burned in suspension)—it is reasonable to allow other high-quality fuels as the primary fuel. Consequently, tall oil would also be allowed as a primary fuel. Tall oil is fuel derived from vegetable and rosin fatty acids and has a heating value comparable to fuel oil.

We specifically request comment on whether a condition to require a minimum of 50% primary (generally fossil) fuel is appropriate to maintain a hot, stable flame to ensure good combustion of ECF. Any comments recommending an alternative minimum limit for the primary fuel firing rate must include supporting information in order for the Agency to be able to consider it for final action.

4. The Boiler Load Must Be 40% or Greater

A condition of the proposed exclusion would require the ECF boiler to operate at 40% load (i.e., the heat input at any time when ECF is fired must be at least 40% of the maximum rated boiler heat input) or greater to ensure a hot, stable flame. At low loads, higher excess air rates are used to improve fuel/air mixing. The increased excess air rates, however, can also cool the flame zone and even make the flame unstable (e.g., as a candle flame flickers in a breeze), thereby increasing the likelihood of flameout. These conditions can result in reduced combustion efficiency. Although a lower boiler load could have been selected within the reasonable range of 25% to 40% of maximum load, we believe it is appropriate to adopt a value at the high end of the range to be conservative given that ECF can contain concentrations of certain hydrocarbons and oxygenates higher than the specifications listed in Table 1 to § 261.38. We also note that a minimum load requirement of 40% would be consistent with the requirement for hazardous waste boilers under § 266.110 that elect to waive the DRE performance standard under operating conditions that ensure optimum combustion efficiency.

We specifically request comment on whether a condition on minimum boiler load of 40 percent is appropriate to maintain a hot, stable flame and thus ensure good combustion conditions. Any comments recommending an alternative minimum boiler load must include supporting information in order for the Agency to be able to consider it for final action.

5. The ECF Must Have an As-Fired Heating Value of 8,000 Btu/lb or Greater

A condition of the proposed exclusion would require the ECF to have an as-fired heating value of 8,000 Btu/lb or greater. This is a reasonable minimum heating value that could have been selected within the range of 5,000 Btu/lb to 10,000 Btu/lb because: (1) It is the minimum heating value of fossil fuels normally fired in industrial boilers (i.e., subbituminous coal); and (2) it would help ensure that a hot, stable primary fuel flame is maintained. We also note that more than 90% of the candidate waste fuel streams identified by generators had heating values greater than 8,000 Btu/lb.
45

45
Letter from American Chemistry Council (Carter Lee Kelly, Leader, Waste Issues Team, and Robert A. Elam, Director, Regulatory Affairs, Waste Issues Team) to Robert Springer and Matt Hale, USEPA, dated November 24, 2003.

Although ECF, like comparable fuel, would need to have a heating value of 5,000 Btu/lb as-generated (or after bona fide treatment as a hazardous waste), it must have a minimum heating value of 8,000 Btu/lb as-fired. Accordingly, ECF may be blended with fuels (including comparable fuel) other than hazardous waste to achieve an as-fired heating value of at least 8,000 Btu/lb. However, any fossil fuel used to blend ECF to achieve the minimum 8,000 Btu/lb heating value requirement could not be counted to achieve the proposed condition that the boiler must have a minimum firing rate of 50% primary fuel.

We specifically request comment on whether a condition to require that ECF have an as-fired heating value of 8,000 Btu/lb or greater is appropriate to help ensure that the hazardous compounds that may be present in the ECF at high concentrations are destroyed to levels comparable to oil-fired boiler emissions. Any such comments on alternative ECF heating values must include supporting

information in order for the Agency to be able to consider it for final action.

6. ECF Must Be Fired Into the Primary Fuel Flame Zone

As a condition of the proposed exclusion, ECF must be fired into the primary fuel flame zone to avoid, potentially, total ignition failure—a combustion failure mode characterized by poor combustion, high emissions of unburned organic compounds, but potentially low CO emissions. Under this combustion failure mode, organic compounds in ECF would not be exposed to the hot flame zone and may be simply volatilized absent combustion. Thus, under this failure mode, low CO emissions may not be indicative of good combustion conditions.

As a practical matter, firing waste fuels (or any fuels) directly into the flame zone of the boiler is standard operating practice. Directing the fuel burner in a direction that avoided the flame zone would normally occur only inadvertently. Nonetheless, we believe it is prudent to propose this condition to highlight its importance in achieving good combustion conditions.

We specifically request comment on whether a condition to require that ECF be fired into the primary fuel flame zone is appropriate to help ensure that the hazardous compounds that may be present in the ECF at high concentrations are destroyed to levels comparable to oil-fired boiler emissions. Any such comments must include supporting information in order for the Agency to be able to consider it for final action.
46

46
Please note that we also request comment on conditions (other than proper atomization) that may be appropriate for the ECF firing system in Part Two, Section VII, in response to comments from a peer reviewer.

7. The ECF Firing System Must Provide Proper Atomization

As a condition of the proposed exclusion, the ECF firing system must provide proper atomization to ensure that the ECF droplets are not too large for optimum volatilization. An organic compound must be vaporized and mixed with air before combustion can occur. The quicker ECF and its constituents are vaporized and the more completely the volatilized compounds are mixed with air, the more rapid and efficient the combustion and destruction of organic constituents. Firing systems that atomize liquid fuels to form small droplets increase the rate of vaporization by providing a larger surface area per volume of fuel to absorb heat from the flame.

We are proposing to allow the use of virtually all atomization systems commonly used to fire liquid fuels.
47

We are, however, proposing to restrict the maximum size of solids that may be present in liquid fuels that meet the viscosity specification of 50 cSt—the as-fired ECF must pass through a 200 mesh screen. This would ensure that the appropriate droplet size is achieved (to ensure volatilization and destruction of organic compounds) and minimize plugging of the firing nozzle. The acceptable atomization systems are air, steam, mechanical, or rotary cup atomization systems.
48

47
A simple lance (essentially an open pipe without any means of atomization), however, could not be used to fire ECF.

48
Engineering Science, “Background Information Document for the Development of Regulations to Control the Burning of Hazardous Waste in Boilers and Industrial Furnaces, Volume I: Industrial Boilers,” January 1987, pp. 4-89 to 4-96.

a. Air or steam atomization.
Air or steam atomization systems use air or steam to break up the fuel into small droplets. Under ordinary operations, high pressure steam or air provided at 30 to 150 psig produces much smaller droplets than other atomization systems. Because of the cost of providing high pressure air and where steam is not readily available, low pressure (1-5 psig) burners are sometimes used.

b. Mechanical atomization.
Mechanical atomizers break up the fuel into small droplets by forcing it through a small, fixed orifice. A strong cyclonic or whirling velocity is imparted to the fuel before it is released through the orifice. Combustion air is provided around the periphery of the conical spray of fuel. The combination of combustion air introduced tangentially into the burner and the action of the swirling fuel produces effective atomization.

The size of the droplets produced by mechanical atomization is a function principally of the fuel viscosity and the fuel pressure at the atomizing nozzle. The pressure required to produce a droplet size conducive to optimum combustion efficiency depends on the volatility of the fuel. Highly volatile materials can volatilize rapidly, even from larger droplets, and, thus, can be fired at pressures of 75 to 150 psig. Less volatile fuels may require an atomization pressure as high as 1,000 psig to form droplets small enough to rapidly volatilize.

Given that fuel pressure is an important factor in determining droplet size, we considered whether it would be appropriate to propose to limit the minimum fuel pressure as a condition of the exclusion.
49

Optimum fuel pressure to produce an optimum droplet size, however, is a function of fuel volatility and fuel/air mixing. Thus, it is not practicable to propose specific limits on minimum fuel pressure. Rather, we are proposing that the boiler owner or operator be required to maintain fuel pressure within the atomization system design range considering the viscosity and volatility of the waste fuel, the fuel/air mixing system, and other appropriate parameters. This approach would allow the atomization system manufacturer or designer (e.g., if designed and fabricated on-site) the necessary flexibility to determine an acceptable fuel pressure considering the specifics of the situation. If fuel pressure is not maintained at appropriate levels to ensure small droplet size and optimum combustion efficiency or, if for any other reason the boiler does not achieve maximum combustion efficiency, the boiler may not be able to achieve CO levels below 100 ppmv.

49
Mechanical atomizers are susceptible to erosion of the orifices in the firing nozzle. Erosion can increase the size of the orifice resulting in decreased fuel pressure and increased droplet size. Limits on minimum fuel pressure, thus, would ensure that droplet size remains optimized during the course of operations by either increasing fuel pressure as the nozzle erodes and, more likely, replacing an eroded firing nozzle.

c. Rotary cup atomization.
The rotary cup atomizer uses centrifugal force to break up the fuel into droplets. It consists of an open cup mounted on a hollow shaft. The fuel is pumped at low pressure through the hollow shaft to the cup which is rotating at several thousand revolutions per minute. A thin film of the fuel is centrifugally torn from the tip of the cup. As centrifugal force drives the fuel off the cup, combustion air is admitted in a rotation counter to the direction of the cup. This counter motion of the air breaks up the conical sheets of fuel into droplets and provides turbulence for mixing the droplets with air.

Rotary cup atomizers are typically used on smaller boilers (e.g., less than 30 MM Btu/hr heat input) because the maximum capacity of the largest unit is about 1,400 pounds of fuel per hour. In addition, rotary cup atomizers are not often installed on new boilers because it is difficult to achieve optimum fuel/air mixing over a wide range of fuel flow rates. Rotary cup atomizers are used because they are relatively inexpensive, they can handle fuels with relative high viscosities ranging up to 40 to 72 cSt,
50

and they are relatively insensitive to solid impurities in the fuel and can handle waste fuels with solids that can pass through a 34 to 100 mesh screen.
51

50
ECF could not have a viscosity exceeding 50 cSt given that it would be subject to the same specifications that apply to existing comparable fuel, except that the specifications for certain hydrocarbons and oxygenates would not apply.

51
We propose that ECF must be able to pass through a 200 mesh (74 micron) sieve to ensure that particles are small enough to ensure volatilization and destruction of organic compounds.

Droplet size is related primarily to the viscosity and flow rate of the fuel and rotational speed of the cup. Resulting combustion efficiency is related to volatility of the fuel and fuel/air mixing. Although it is impracticable to control these variables in a regulatory context, manufacturers and boiler owners and operators have ample experience with rotary cup atomizers to design units that achieve efficient combustion. Thus, we are proposing that owners and operators demonstrate that the as-fired fuel has a volatility within the design parameters of the firing system and limit fuel flow rates consistent with the design parameters of the firing system. As discussed above, relative to mechanical atomization systems, if, in fact, the device does not produce droplet sizes and fuel/air ratios conducive to maintaining high combustion efficiency, the boiler may not be able to achieve CO levels below 100 ppmv.

We specifically request comment on whether these conditions for atomization of ECF are appropriate to help ensure that the hazardous compounds that may be present in the ECF at high concentrations are destroyed to levels comparable to oil-fired boiler emissions. Any such comments must include supporting information in order for the Agency to be able to consider it for final action.
52

52
Please note that we also request comment on conditions that may be appropriate for the ECF firing system in Part Two, Section VII, in response to comments from a peer reviewer.

8. Dioxin/Furan Controls for Boilers Equipped With an ESP or FF

If a boiler is equipped with an electrostatic precipitator (ESP) or fabric filter (FF) and does not fire coal as the primary fuel,
53

we are proposing that the combustion gas temperature at the inlet to the ESP or FF be continuously monitored, be linked to the automatic ECF feed cutoff system, and not exceed 400 °F on an hourly rolling average. These proposed conditions would ensure that the post-combustion, heterogeneous surface-catalyzed formation of dioxin/furan in an ESP or FF is minimized so that emissions from burning ECF remain at least comparable to those from burning fossil fuels and remain at levels that are protective of human health and the environment.

53
Note that oil-fired boilers are generally not equipped with a particulate matter control device and that the fraction that are so-equipped are typically equipped with wet scrubbers rather than an ESP or FF. Thus, we would expect that this condition would only apply to a small percentage of boilers that choose to burn ECF. See the memorandum from Jim Eddinger, EPA, to EPA Docket No. OAR-2002-0058, entitled, “Revised MACT Floor Analysis for the Industrial, Commercial, and Institutional Boilers and Process Heaters National Emission Standards for Hazardous Air Pollutants Based on Public Comments,” dated February 2004, Section 6.4.2.

We are basing these proposed conditions on information and data gathered from the recently promulgated NESHAP standards for hazardous waste combustors. See 70 FR 59402. Specifically, we have determined that the surface-catalyzed formation of dioxins/furans across an ESP or FF can be significant when gas temperatures exceed 400 °F.
54

When gas temperatures are below 400 °F (and the combustor is operating under good combustion conditions as evidenced by CO below 100 ppmv), however, dioxin/furan emissions are generally below 0.40 ng TEQ/dscm, the emission standard for most hazardous waste combustors.
55

54
USEPA, “Technical Support Document for HWC MACT Standards, Volume III: Selection of MACT Standards and Technologies,” July 1999, Section 3.0; USEPA, “Technical Support Document for HWC MACT Standards, Volume IV: Compliance with the HWC MACT Standards,” September 2005, Section 3.2, and USEPA, “Technical Support Document for HWC MACT Standards, Volume III: Selection of MACT Standards,” September 2005, Section 13.3.1.1.

55
See §§ 63.1217, 63.1219, and 63.1220. See also USEPA, USEPA, “Draft Technical Support Document for Expansion of the Comparable Fuel Exclusion,” May 2007, Section 5.

Boilers burning coal as the primary fuel would not be required to monitor combustion gas temperature at the inlet to an ESP or FF as a condition of the exclusion, however. We determined during development of the NESHAP for coal-fired boilers that burn hazardous waste that sulfur contributed by the coal is a dominant control mechanism because the sulfur inhibits formation of dioxins/furans.
56

Please note, however, that a peer reviewer questioned whether the low sulfur coal that some ECF boilers may burn would also inhibit formation of dioxins/furans. We believe that low sulfur coals would also inhibit formation of dioxins/furans (and, thus, a condition to limit the gas temperature at the inlet to the ESP or FF would not be needed), but request comment and supporting information on opposing views. See discussion in Section VII below.

56
USEPA, “Technical Support Document for HWC MACT Standards, Volume III: Selection of MACT Standards,” September 2005, Section 14.1.1.

We are further proposing an hourly averaging period for the temperature limit, rather than a longer averaging period, because there is a nonlinear relationship between gas temperature at the ESP or FF and dioxin/furan emissions. Consequently, a longer averaging period would allow higher temperatures to be offset by lower temperatures, even though dioxin/furan emissions at the higher temperatures could be exponentially higher than emissions at the lower temperatures, and, thus, average dioxin/furan emissions would be substantially higher than if temperatures had been maintained at the average temperature.
57

57
USEPA, “Technical Support Document for HWC MACT Standards, Volume IV: Compliance with the HWC MACT Standards,” September 2005, Section 2.2.3.

We also believe that there are factors other than high gas temperature at the inlet to an ESP or FF that may contribute to the post-combustion formation of dioxin/furan in boilers, but these situations would not occur for boilers burning ECF under the proposed conditions. For example, we have dioxin/furan emissions data for nine three-run test conditions for eight boilers burning liquid hazardous waste fuel and equipped with wet scrubbers, and two of the boilers have emissions exceeding 0.40 ng TEQ/dscm.
58

Although the wet scrubbers on these boilers preclude surface-catalyzed dioxin/furan formation across the emission control device, the boilers nonetheless have high dioxin/furan emissions—1.4 ng TEQ/dscm and 0.44 ng TEQ/dscm. We note, however, that both of these boilers are firetube boilers and one burns waste fuel containing 60% by weight chlorine. Firetube boilers would not be allowed to burn ECF under the conditions proposed today for reasons discussed above and, in addition, the chlorine level in the waste fuel for one of the boilers is orders of magnitude higher than the specification for chlorine in Table 1 to § 261.38.
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It is speculated that the higher tube surface to combustion gas

volume ratio for a firetube boiler compared to a watertube boiler may increase the possibility of combustion gas flow over particulate matter that has adhered to the tubes within the 400-750 °F temperature window, which is conducive to surface-catalyzed formation of dioxins/furans.

58
USEPA, “Draft Technical Support Document for Expansion of the Comparable Fuel Exclusion, May 2007, Section 5.

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Although chlorine content of the feed is generally not considered a primary factor in formation of dioxin/furan (especially when other factors may predominate, such as high gas temperature at the inlet to the ESP or FF) because extremely small amounts of chlorine are sufficient to provide the chlorine for dioxin/furan formation, we are nonetheless concerned enough about chlorine content in the feed to require that hazardous waste combustors operate within the range of normal chlorine federate levels during performance testing to document compliance with the dioxin/furan emission standard. Thus, chlorine content of the feed may be a significant factor that could affect dioxin/furan formation. See USEPA, “Technical Support Document for HWC MACT Standards, Volume IV: Compliance with the HWC MACT Standards,” September 2005, Section 3.3.

We also have dioxin/furan emissions data for 11 three-run test conditions for six different boilers that burn hazardous waste and that are equipped with an ESP or FF. Gas temperatures at the ESP or FF were generally below 400 °F.
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Only two test conditions (from two boilers) were above 0.4 ng TEQ/dscm. One boiler (which would be ineligible to burn ECF because it is a firetube boiler) had emissions of 0.66 ngTEQ/dscm during one test condition. This unit burns mixed waste with levels of chlorine and metals above the specifications in Table 1 to § 261.38. The second boiler (a watertube boiler), however, had average emissions of 2.4 ng TEQ/dscm. Although the FF for this boiler was operated slightly above 400 °F, we note that this boiler burned waste fuel containing nickel at levels orders of magnitude higher than the specification identified in Table 1 to § 261.38. Nickel, as well as copper and iron, have been suggested to be responsible for the catalytic reactions that lead to post-combustion formation of dioxins/furans.
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USEPA, “Draft Technical Support Document for Expansion of the Comparable Fuel Exclusion, May 2007, Section 5.3.3.

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USEPA, “Technical Support Document for HWC MACT Standards, Volume IV: Compliance with the HWC MACT Standards,” September 2005, p. 3-17.

Therefore, based on the data described above, we believe that the scenarios that resulted in high dioxin/furan emissions when burning hazardous waste fuels would not occur for ECF boilers and that a proposed condition that would limit the gas temperatures at the inlet to a dry particulate matter control device to 400 °F should control dioxin/furan emissions generally to below 0.40 ng TEQ/dscm.
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Moreover, we note that we have dioxin/furan emissions data for 38 three-run test conditions representing 32 different boilers burning hazardous waste fuel and not equipped with an emissions control device where the test condition average emissions were quite low—below 0.10 ng TEQ/dscm. In addition, we have dioxin/furan emissions data for 15 runs for oil-fired industrial boilers (i.e., not burning hazardous waste), and the average emissions were 0.013 ng TEQ/dscm and the maximum emissions were 0.042 ng TEQ/dscm.
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This is further confirmation indicating that dioxin/furan emissions from boilers burning ECF under the proposed conditions should be quite low.

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We discussed previously in the text in Part Two, Section I.B, that an abbreviated comparative risk assessment for dioxin/furan emissions from hazardous waste boilers that meet the design conditions (i.e., watertube steam boiler that is not stoker-fired) for an ECF boiler indicates that dioxin/furan emissions from such a boiler are not likely to pose a hazard to human health or the environment.

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USEPA, “Draft Technical Support Document for Expansion of the Comparable Fuel Exclusion, May 2007, Section 3.4.

III. What Restrictions Would Apply to Particular Hydrocarbons and Oxygenates?

The toxicity, persistence and bioaccumulation potential for the 37 hydrocarbons and oxygenates for which specifications have been established in Table 1 to § 261.38 varies over a wide range. In addition, we acknowledge that when ECF with potentially higher concentrations of certain hydrocarbons and oxygenates than fuel oil is burned, even under good combustion conditions, emissions of hazardous organics maybe somewhat higher than those from burning fossil fuel because combustion is generally a percent-reduction process. Therefore, to ensure that the emissions from burning ECF as a fuel under the conditions proposed today remain protective, we propose to retain the specifications for compounds that can pose a high hazard—naphthalene and PAHs—and to restrict the firing rate of ECF containing concentrations of compounds that can pose a lower, but substantial hazard—benzene and acrolein. See
Safe Food and Fertilizers
, 353 F. 3d at 1271 (exclusion from the definition of solid waste can be justified by low risk posed by the recycling practice).

We explain below the rationale for the approach we use to categorize the 37 hydrocarbons and oxygenates for which specifications are established in Table 1 to § 261.38, according to their relative hazard to human health and the environment.

A. What Is the Rationale for the Relative Hazard Characterization Scheme?

We categorized the 37 hydrocarbons and oxygenates for which specifications have been established in Table 1 to § 261.38 as to their relative hazard.
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We assigned the highest hazard constituents to Category A, the constituents that pose intermediate hazard to Category B, and the other constituents to Category C. As mentioned above, we are proposing to retain the specifications for the Category A constituents, restrict the feedrate of the Category B constituents, and not apply the specifications in Table 1 to the Category C constituents. We discuss below the procedure for categorizing the constituents.

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Please note that we have conducted an independent peer review of our ranking procedures. See discussion in Part Two, Section VII, of the preamble.

First, we used the Waste Minimization Prioritization Tool (WMPT)
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to rank the 37 hydrocarbons and oxygenates. The WMPT is a peer-reviewed methodology which provides a screening-level assessment of potential chronic (i.e., long-term) risks to human health and the environment, considering the chemicals' toxicity, persistence and bioaccumulation potential.
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USEPA, “Waste Minimization Prioritization Tool Background Document for the Tier III PBT Chemical List,” 2000.

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After several rounds of internal expert and public comments, EPA used the current version of the WMPT as the initial step in the process of identifying the initial pool of priority chemicals that are national priorities for voluntary pollution prevention activities across the agency. EPA determined the initial pool of priority chemical candidates based on their rank. The rankings are based on the higher of available scores for human health concern (i.e., the sum of the scores for persistence, bioaccumulation, and human toxicity) and ecological concern (i.e., the sum of the scores for persistence, bioaccumulation, and ecological toxicity). The priority chemical candidate pool was limited to those chemicals with WMPT scores of 8 or 9 (on a scale of 3 to 9). For a more detailed description of the WMPT development process, see USEPA, “Waste Minimization Prioritization Tool Background Document for the Tier III PBT Chemical List,” 2000. The specific use of the current version of the WMPT rankings in developing the RCRA Prioirity Chemicals List is documented in the Tier III Chemical List Docket.

The WMPT scoring method produces chemical-specific scores for a screening-level risk-based ranking of chemicals.
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The scoring method was designed to generate an overall chemical score that reflects the potential of a chemical to pose risk to either human health or ecological systems. A measure of human health concern is derived, consistent with the risk assessment paradigm, by jointly assessing the chemical's human toxicity and potential for exposure. Similarly, a measure of the ecological concern is derived by jointly assessing the chemical's ecological toxicity and potential for exposure. The WMPT uses a small number of relatively simple measures to represent the toxicity (e.g., oral Cancer Slope Factor) and exposure potential (e.g., Bioaccumulation Factor) of each chemical, consistent with a screening-level approach and with other systems of this type.

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USEPA, “Draft Technical Support Document for Expansion of the Comp

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3AE7-11130. Public record. Not legal advice.