United States Environmental Protection Agency, Region 9 

Air Division 

Technical Support Document 

for 

EPA’s Notice of Rulemaking 

for the 

California State Implementation Plan 

Yolo-Solano Air Quality Management District’s 

Rule 2.43, Biomass Boilers 

Prepared by: Idalia Perez 

January 2012 
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Yolo-Solano Air Quality Management District (YSAQMD) 

Submitted Rule 

YSAQMD Rule 2.43, Biomass Boilers: 

§ Adopted: November 10, 2010 

§ Submitted: April 5, 2011 

§ Determined complete: May 6, 2011 

Previous Rule Submittals 

There are no outstanding submittals of Rule 2.43. 

SIP-Approved Rule 

There is currently no SIP-approved version of Rule 2.43. 

Rule Summary 

Rule 2.43 regulates emissions of oxides of nitrogen (NOx) and carbon monoxide (CO) from 

boilers and steam generators that use biomass as fuel and that have a heat input rating of greater 

than 5 MMBtu/hour. 

The emission limits in the rule are (Section 301): 

§ 90 ppm of NOx at 3% O2, 24-hour block average 

§ 400 ppm of CO at 3% O2, 24-hour block average 

The rule language includes exemptions (Section 110), definitions (Section 200) and startup and 

shutdown provisions (Section 302). Monitoring and recordkeeping requirements are contained in 

various provisions in Sections 303, 304, 400, 500 and 600.

Effects on Emissions 

The District does not expect emissions reductions due to the implementation of the rule because 

the only existing facility that is subject to the rule already meets the emission requirements. 

Rule Evaluation Criteria 

We have primarily used the following three criteria to evaluate Rule 2.43: 

1. Rule Stringency – Section 172(c)(1) of the Clean Air Act (CAA) requires 

nonattainment areas to implement all reasonably available control measures 

(RACM), including such reductions in emissions from existing sources in the area 

as may be obtained through the adoption, at a minimum, of reasonably available 

control technology (RACT), as expeditiously as practicable. In addition, ozone 

nonattainment areas classified as moderate or above must require RACT for all 

major sources of NOx and VOCs. CAA § 182(b)(2) & (f); 40 CFR § 51.912(a). 

The YSAQMD regulates an ozone nonattainment area that is classified as Severe15 under both the 1-hour ozone and 8-hour ozone standards. 40 C.F.R. § 81.305 

(2010).1 Therefore, submitted Rule 2.43 must fulfill RACT requirements for NOx.

 

1 YSAQMD also regulates a nonattainment area under the 2006 24-Hour PM2.5 National Ambient Air Quality 

Standard. 40 C.F.R. § 81.305 (2010). By December 14, 2012, California must submit a revision to the State 
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2. Enforceability – CAA section 110(a)(2)(A) requires that regulations submitted to 

EPA for approval into a State Implementation Plan (SIP) must be clear and 

legally enforceable. 

3. SIP Revisions - CAA section 110(l) prohibits EPA from approving any SIP 

revision that would interfere with any applicable requirement concerning 

attainment and reasonable further progress (RFP) or any other applicable 

requirement of the CAA. In addition, CAA section 193 prohibits the modification 

of any SIP-approved control requirement in effect before November 15, 1990, in a 

nonattainment area.

Guidance and policy documents that we used to define specific enforceability, RACT and 

RACM requirements include the following: 

• Issues Relating to VOC Regulation, Cutpoints, Deficiencies, and Deviations (the “Blue 

Book”), US EPA, OAQPS (May 25, 1988). 

• Guidance Document for Correcting Common VOC and Other Rule Deficiencies, EPA 

Region IX (August 21, 2001, the “Little Bluebook”). 

• State Implementation Plans; General Preamble for the Implementation of Title I of the 

Clean Air Act Amendments of 1990, 57 FR 13498 (April 16, 1992); 57 FR 18070 (April 

28, 1992). 

• State Implementation Plans; Nitrogen Oxides Supplement to the General Preamble; 

Clean Air Act Amendments of 1990 Implementation of Title I; Proposed Rule, 57 FR 

55620 (Nov. 25, 1992). 

• Determination of Reasonably Available Control Technology and Best Available Retrofit 

Control Technology for Industrial, Institutional, and Commercial Boilers, Steam 

Generators, and Process Heaters, CARB (July 18, 1991). 

http://www.arb.ca.gov/ractbarc/boilers.pdf

• Alternative Control Techniques Document-- NOx Emissions from 

Industrial/Commercial/Institutional (ICI) Boilers, US EPA 453/R-94-022 (March 1994). 

http://www.epa.gov/ttn/catc/dir1/icboiler.pdf

• Alternative Control Techniques Document-- NOx Emissions from Utility Boilers, US 

EPA 452/R-93-008 (March 1994). http://www.epa.gov/ttn/catc/dir1/utboiler.pdf

• State Implementation Plans (SIPs): Policy Regarding Excess Emissions During 

Malfunctions, Startup and Shutdown from Steven A. Herman, Assistant Administrator for 

Enforcement and Compliance Assurance, and Robert Perciasepe, Assistant Administrator 

for Air and Radiation, September 20, 1999. 

Evaluation of Rule Stringency 

As noted above, submitted Rule 2.43 must fulfill RACT requirements for NOx. See CAA § 

182(b)(2) and (f); 40 CFR 51.912(a). EPA issues two types of guidance to assist states in 

 

Implementation Plan (SIP) for this nonattainment area that provides for, among other things, implementation of all 

RACM as expeditiously as practicable (including RACT for existing sources). CAA § 172(a)(2)(A), (b) & (c)(1), 74 

FR 58689 (Nov. 13, 2009). EPA will take action on this RACM demonstration in a separate rulemaking. 
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determining what control techniques meet the RACT requirement: control techniques guidelines 

(CTGs) and alternative control techniques (ACTs). CTGs establish the presumptive level of 

control meeting RACT, whereas ACTs describe available control techniques and their cost 

effectiveness, but do not define presumptive RACT levels. 70 FR 71654 (Nov. 25, 2005). 

EPA has not issued a CTG for NOx for boilers, but in 1994 EPA issued an ACT Document for 

NOx emissions from Industrial/Commercial/Institutional Boilers (1994 ACT). 

As part of our evaluation of Rule 2.43, we reviewed the 1994 ACT, which identifies NOx 

emission levels for biomass-fueled boilers ranging from 24 ppm to 187 ppm at 3% O2, based on 

the use of SNCR controls with ammonia or urea injection. (1994 ACT at Appendix B, pages 

B20-B21) This wide range of emission levels reflects the broad technical diversity among the 

types of boilers that fire biomass as fuel, including stokers, circulating fluidized bed boilers and 

bubbling fluidized bed boilers. It also reflects the variety of fuels that the term “biomass” covers, 

including various kinds of plant materials, wood materials and agricultural wastes. 

In addition to reviewing the 1994 ACT, we obtained information about NOx emission limits in 

permits for biomass-fueled boilers from the RACT/BACT/LAER Clearinghouse (RBLC, 

http://cfpub.epa.gov/RBLC/). We searched the RBLC for permits dated between 2001 and 2011 

with process utility code 11.120 (Utility and Large Industrial Size Boilers/Furnaces (>250 

MMBtu/hr), Biomass). The NOx emission limits in these permits range between 0.01 lb/MMBtu 

(RBLC ID = GA-0132, issued 2008) to 0.6 lb/MMBtu (RBLC ID = NH-0013, issued 2004), both 

for a 30 day rolling averaging period. These limits translate to a range of approximately 8 to 466 

ppm at 3% O2. According to the RBLC, the 8 ppm limit has not been verified. 

We also reviewed rules from other air districts in California that regulate biomass boilers. San 

Joaquin Valley Unified Air Pollution Control District’s (SJVUAPCD) Solid Fuel Fired Boiler 

Rule (Rule 4352, adopted May 18, 2006) has a NOx emission limit for biomass boilers of 115 

ppm at 3% O2 on a 24-hour block average. On October 1, 2010, EPA finalized a limited 

disapproval of SJVUAPCD rule because we determined that SJVUAPCD had not adequately 

demonstrated that the NOx limits in the rule satisfied RACT. (75 FR 60623) SJVUAPCD has 

since revised Rule 4352 (adopted on December 15, 2011) and included a NOx limit for biomass 

fired boilers of 90 ppm at 3% O2 on a 24-hour block average. On September 6, 2011, we 

proposed a limited approval, limited disapproval of Placer County Air Pollution Control 

District’s (PCAPCD) Rule 233, Biomass Boilers, because we determined that PCAPCD had not 

adequately demonstrated that the NOx limits in the rule satisfied RACT. (76 FR 54993) The rule 

has a NOx limit of 115 ppm at 12% CO2 on a 3-hour block average, which is approximately 148 

ppm at 3% O2. Sacramento Metro Air Quality Management District’s (SMAQMD) Rule 411 

(adopted on August 23, 2007) has a NOx limit of 70 ppm at 12% CO2, which is approximately 

100 ppm at 3% O2. There are no facilities in SMAQMD that are subject to this limit thus this 

limit has not been shown to be achievable. 

According to the Staff Report for Rule 2.43, there is one existing source in YSAQMD, 

Woodland Biomass Power Ltd. Similar to other biomass burning facilities, this facility has a 

diverse fuel supply which has differing heating values and nitrogen content and can lead to 

variable NOx emissions. These short term spikes caused by fuel variability necessitate a 24-hour 

averaging period to ensure that compliance can be achieved. 
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The NOx emission limit in Rule 2.43 is 90 ppm at 3% O2 on a 24-hour block average. This limit 

is as stringent as the most stringent limits in other prohibitory rules in California that have been 

demonstrated to be achieved in practice. The limits in Rule 2.43 are consistent with the low end 

of ranges found in the 1994 ACT and of permit limits found in the RBLC. Since no CTG has 

been issued recently for this activity, we do not have clear national guidance defining 

presumptive RACT. However, we believe the analysis summarized above sufficiently 

demonstrates that Rule 2.43 implements RACT. 

Evaluation of Enforceability and SIP Revision Criteria 

Recordkeeping and other compliance provisions in the rule ensure that the requirements are 

adequately enforceable. 

The submitted is a new addition to the SIP, strengthening the requirements of the SIP. Therefore, 

we propose to determine that an approval of the submittal would comply with CAA sections 

110(l) and 193 because (1) the proposed SIP revision would not interfere with the on-going 

process for ensuring that requirements for RFP and attainment of the NAAQS are met, and (2) 

the submitted SIP revision is more stringent than the existing SIP requirements. 

Suggested Rule Improvements 

Although not currently basis for rule disapproval, EPA recommends that the YSAQMD include 

PM2.5 and SOx emission limits in the next revision of Rule 2.43. 

Recommendation 

EPA staff recommends a limited approval and limited disapproval of YSAQMD Rule 2.43 under 

CAA sections 110(k)(3) and 301(a). 

Other References 

1. RBLC permit information (GA-0132, NH-0013) 

2. Submitted Rule 2.43 

3. Staff Report for Rule 2.43