United States Environmental Protection Agency, Region 9

Air Division

Technical Support Document

for

EPA’s Notice of Rulemaking

for the

California State Implementation Plan

Placer County Air Pollution Control District’s

Rule 233, Biomass Boilers

Prepared by: Idalia Perez

July 2011
Placer County Air Pollution Control District (PCAPCD)

Submitted Rule

PCAPCD Rule 233, Biomass Boilers:

 Adopted: December 10, 2009

 Submitted: May 17, 2010

 Determined complete: June 8, 2010

Previous Rule Submittals

There are no outstanding submittals of Rule 233. PCAPCD adopted a previous version of Rule 

233 on October 11, 2007 and it was submitted to EPA on March 7, 2008. This rule was officially 

withdrawn on November 5, 2008.

SIP-Approved Rule

 Adopted: October 6, 1994

 Approved by EPA: April 30, 1996 (61 FR 18959)

Rule Summary

Rule 233 regulates emissions of oxides of nitrogen (NOx) and carbon monoxide (CO) from 

biomass boilers and steam generators that have a heat input rating of less than 500 million British 

Thermal Units per hour (MMBtu) and a potential to emit 25 tons or more of NOx per year.

Changes to the rule

The District amended Rule 233 on October 11, 2007 to address concerns from industry.

Regulated facilities were having difficulty meeting the parts per million (ppm) NOx limits during 

start-up and shutdown due to the carbon dioxide (CO2) correction in this form of the standard.

Facilities were able to meet their permitted pounds per hour (lb/hour) NOx limit during the same 

periods of time because this form of the emission limit does not have a CO2 correction. The NOx 

limits in the rule are shown in the following table. 

Type of Boiler Limits during normal 

operations (ppm) 

Approximate limits during 

normal operations (lb/hour)1

Limits during startup 

shutdown (lb/hour)

Circulating Fluidized Bed 115 95.1 35

Stoker 115 59.7 37.6

The main changes to Rule 233 to address the facilities’ concerns were changes in the definitions 

of start-up, shutdown and the replacement of the existing ppm limits with lb/hour limits during 

these periods. Additionally, a 400 ppm or 1000 ppm limit for CO was added (depending on 

boiler type), the option for 50% reduction of NOx emissions from uncontrolled levels as the limit 

for NOx was eliminated and the method for determining the HHV for fuel was changed from 

ASTM D 2015-85 to ASTM E711.

 

1 These values are not in the text of the rule, but were obtained from an email sent by John Finnell to Idalia Perez on 

4/8/2011. They are calculated based on the respective boiler capacities of the two facilities currently regulated under 

Rule 233. 
Other changes to the rule include added definitions and recordkeeping requirements that improve 

rule clarity and enforceability.

Effects on Emissions

The changes made to Rule 233 have no net effect on emissions. The removal of the 115 ppm 

NOx limit during startup and shutdown will not result in a net increase in emissions because the

115 ppm limit will be replaced by lb/hour limits during startup and shutdown. As indicated by 

the table above, the new limits are more stringent on a lb/hour basis than the 115 ppm limit with 

respect to each of the two facilities that is currently regulated under Rule 233. The new limits 

will not result in a net decrease in emissions, since the limits are already in the facilities’ permits.

Rule Evaluation Criteria 

We have primarily used the following three criteria to evaluate Rule 233:

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. CAA § 182(b)(2) & (f); 40 CFR § 51.912(a). The 

PCAPCD regulates an ozone nonattainment area that is classified as Severe-15 

under both the 1-hr ozone and 8-hr ozone standards. 40 C.F.R. § 81.305 (2010).

2

Therefore, submitted Rule 233 must fulfill RACT requirements for NOx.

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).

 

2

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

Standard (NAAQS). 40 C.F.R. § 81.305 (2010). By December 14, 2012, California must submit a revision to the 

State 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.
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).

Final Rule To Implement the 8-Hour Ozone NAAQS – Phase 2, 70 FR 71612 (Nov. 25, 

2005).

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://nepis.epa.gov/EPA/html/Pubs/pubtitleOAR.htm

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

EPA 452/R-93-008 (March 1994). http://nepis.epa.gov/EPA/html/Pubs/pubtitleOAR.htm

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 233 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 

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 233, 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 translates to a range of approximately 18 to 142 ppm at 12% CO2. 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 5 to 328

ppm at 12% CO2. According to the RBLC, the 5 ppm limit has not been verified. The only 

permit found in the RBLC with a limit with a 3-hour averaging period similar to limit in Rule 

233 is a limit of 0.3 lb/MMBtu, or approximately 164 ppm at 12% CO2 (RBLC ID = AL-0250, 

issued 2010).

We also reviewed rules from other air districts in California that regulate biomass boilers. YoloSolano Air Quality Management Districted adopted a Biomass Boiler Rule (Rule 2.43) on 

November 10, 2010 that limits NOx emissions to 90 ppm corrected to 3% O2 on a 24-hour block 

average. This is approximately equal to 68 ppm at 12% CO2. 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, which translates to approximately 87 ppm at 12% CO2. We recently 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.

Finally, we reviewed source test results for the only two currently existing facilities in Placer 

County that are subject to Rule 233. Source test results for both facilities for 2009 are shown in 

the following table. 

Facility Boiler Emission 

Sierra Pacific Industries, Lincoln 289 MMBtu/hr, stoker 51.2 ppm at 12% CO2

Rio Bravo Rocklin 356.8 MMBtu/hr, CFB 37.6 ppm at 12% CO2

The source test results establish the emission levels that the facilities have been able to achieve in 

practice.

The NOx emission limit in submitted Rule 233 is 115 ppm at 12% CO2 for a rolling 3-hour 

averaging period. This limit, which has been in place since the rule was first adopted in 1994, 

falls in the middle to high end of the range of achievable emission levels for biomass-fired 

boilers shown in the 1994 ACT (approximately 18 to 142 ppm at 12% CO2) and near the middle 

of the range of limits in recent permits for this source category (approximately 5 to 328 ppm at 

12% CO2). The limit is less stringent than those found in the analogous rules of other air districts 

in California. In addition, source test data show that the existing biomass-fired boilers in Placer 

County that are subject to Rule 233 are achieving emission levels significantly below 115 ppm at 

12% CO2. EPA is not aware of any information indicating that these lower emission levels are 

not reasonably achievable in Placer County

Thus, although EPA previously approved Rule 233 as RACT for this source category under the 

1-hour ozone NAAQS, 61 FR 18959 (April 30, 1996), new information indicates that the 

previous RACT determination is no longer appropriate. See 70 FR 71652. We therefore propose 

to determine that the PCAPCD has not adequately demonstrated that the NOx limit in Rule 233 

(115 ppm at 12% CO2) represents RACT.
Evaluation of Enforceability and SIP Revision Criteria 

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

adequately enforceable. The amendment of the Rule addresses EPA concern regarding the startup and shutdown provisions and aligns these provisions with EPA guidance on the matter.

The submitted rule eliminates the less stringent NOx emission limit option and adds a more 

stringent emission limit for CO than the version previously approved into the SIP. As shown in 

the “Changes to the Rule” section above, the new limits for start-up and shutdown periods are 

more stringent than the existing limits for each of the facilities currently subject to the rule. 

Therefore, we propose to determine that a limited approval of the submittal would comply with 

CAA section 110(l) 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 rule previously approved into the SIP. We 

also propose to determine that a limited approval of the submittal would comply with CAA 

section 193 because the submitted SIP revision is more stringent than the rule previously 

approved into the SIP and would insure equivalent or greater emission reductions of NOx and 

CO. 

Rule Deficiency

As explained above under Evaluation of Rule Stringency, we believe that PCAPCD has not 

demonstrated that the NOx emission limits for biomass boilers implement RACT and that the 

NOx emission limits should be lowered to ensure implementation of RACT. Alternatively, 

PCAPCD may submit additional information to demonstrate that lower emission limits are not 

reasonably achievable.

Recommendation

EPA staff recommends a limited approval and limited disapproval of PCAPCD Rule 233 under

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

Other References

1. RBLC permit information (AL-0250, GA-0132, NH-0013)

2. Source test results for Sierra Pacific Industries, Lincoln, 2009

3. Source test results for Rio Bravo Rocklin, 2009

4. Email from John Finnell to Idalia Perez on 4/8/2011

5. Submitted Rule 233

6. Staff Report for Rule 233

7. Current SIP-approved version of Rule 233