1

MEMORANDUM 

DATE: August 17, 2011 

TO: Andy Steckel 

 Sona Chilingaryan 

 U.S. EPA Region 9, Air Division, Rules Office 

FROM: Samir Sheikh, Director Strategies & Incentives 

 San Joaquin Valley Air Pollution Control District 

RE: District Rule 4565 Composting Mitigation Measures & Associated Costs 

The following information is provided by the San Joaquin Valley Air Pollution Control District 

(District) in response to questions that arose during EPA’s review of District Rule 4565 

(Biosolids, Animal Manure, and Poultry Litter Operations), which was adopted by the District 

Governing Board on March 15, 2007. Specifically, EPA expressed concerns regarding the 

implementation of RACT within the composting mitigation measures. The EPA has afforded the 

District the opportunity to address those concerns before proceeding with any 

approval/disapproval action and associated Technical Support Document. 

Generally, the following information demonstrates that composting mitigation measures in 

Rule 4565, as adopted, implement RACT. Given updated cost, emission factor, and control 

efficiency information, District staff are able to demonstrate that requiring additional mitigation 

measures for small and medium facilities is too costly and the cost effectiveness goes beyond 

RACT. Likewise, requiring all large facilities to implement engineered controls during both the 

active and curing phases of composting (class two mitigation measures) also goes beyond RACT 

based on the high cost and the cost-effectiveness evaluation. 

The following discussion addresses the composting facility throughputs, composting-related 

emissions, control measure efficiencies, emissions reductions, costs of reductions to a facility, 

and compost mitigation measure cost effectiveness assumptions and calculations included in 

District Rule 4565 specific to the composting mitigation measures identified in section 5.3 of 

the rule. The following is an excerpt from Rule 4565 showing the composting facility 

requirements: 

 
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Excerpt from Rule 4565 (Biosolids, animal Manure, and Poultry Litter Operations) 

5.3 Composting/Co-composting Facility Requirements 

5.3.1 Operators of composting/co-composting facilities with throughputs less 

than 20,000 wet tons per year shall meet either 5.3.1.1 or 5.3.1.2. 

5.3.1.1 Implement at least three (3) of the Class One mitigation 

measures listed in Table 2. 

5.3.1.2 Implement at least two (2) Class One mitigation measures in 

addition to one (1) Class Two mitigation measure for active 

composting. 

5.3.2 Operators of composting/co-composting facilities with throughputs at least 

20,000 wet tons per year but less than 100,000 wet tons per year shall 

meet either 5.3.2.1 or 5.3.2.2. 

5.3.2.1 Implement at least four (4) of Class One mitigation measures 

listed in Table 2. 

5.3.2.2 Implement at least three (3) Class One mitigation measures in 

addition to one (1) Class Two mitigation measure on active 

composting processes. 

5.3.3 Operators of composting/co-composting facilities with throughputs at least 

100,000 wet tons per year shall meet either 5.3.3.1 or 5.3.3.2. 

5.3.3.1 Implement at least four (4) Class One mitigation measures in 

addition to one (1) Class Two mitigation measure for active 

composting. 

5.3.3.2 Implement at least two (2) Class One mitigation measures, in 

addition to one (1) Class Two mitigation measure for active 

composting and one (1) Class Two mitigation measure for curing 

composting. 
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Table 2 – Composting/Co-composting Facility Mitigation Measures 

Class One Mitigation Measures 

1. Scrape or sweep, at least once a day, all areas where compostable material is 

mixed, screened, or stored such that no compostable material greater than one inch 

(1”) in height is visible in the areas scraped or swept immediately after scraping or 

sweeping, except for compostable material in process piles or storage piles. 

2. Maintain a minimum oxygen concentration of at least five percent (5%), by 

volume, in the free air space of every active and curing compost pile. 

3. Maintain the moisture content of every active and curing compost pile between 

40% and 70%, by weight. 

4. Manage every active pile such that the initial carbon to nitrogen ratio of every pile 

is at least twenty (20) to one (1). 

5. Cover all active compost piles within 3 hours of each turning with one of the 

following: a waterproof covering; at least six (6) inches of finished compost; or at 

least six (6) inches of soil. 

6. Cover all curing compost piles within 3 hours of each turning with one of the 

following: a waterproof covering; at least six (6) inches of finished compost; or at 

least six (6) inches of soil. 

7. Implement an alternative Class One mitigation measure(s) not listed above that 

demonstrates at least a 10% reduction, by weight, in VOC emissions. 

Class Two Mitigation Measures 

8. Conduct all active composting in aerated static pile(s) vented to a VOC emission 

control device with a VOC control efficiency of at least 80% by weight. 

9. Conduct all active composting in an in-vessel composting system vented to a VOC 

emission control device with a VOC control efficiency of at least 80% by weight. 

10 Conduct all curing composting in aerated static pile(s) vented to a VOC emission 

control device with a VOC control efficiency of at least 80% by weight. 

11 Conduct all curing composting in an in-vessel composting system vented to a VOC 

emission control device with a VOC control efficiency of at least 80% by weight. 

12. Implement an alternative Class Two mitigation measure(s) not listed above that 

demonstrates at least 80% reduction, by weight, in VOC emissions. 

 Link to complete rule: http://www.valleyair.org/rules/currntrules/r4565.pdf 
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Rule 4565 Composting Facility Throughputs 

Composting facilities subject to Rule 4565 fall into one of three categories based on the tons of 

compost delivered to the facility for processing (throughput): those with throughputs less than 

20,000 tons per year; those with at least 20,000 tons, but not more than 100,000 tons per year; 

and those with throughputs greater than 100,000 tons per year. For ease of discussion, this 

document refers to these facilities as small, medium, and large, respectively. For calculation 

purposes, facility throughputs used for small, medium, and large are 10,000, 50,000, and 

100,000 tons per year, respectively. 

While most of the Valley’s existing large compost facilities have throughputs much greater than 

100,000 tons per year, the scaling of facility size also increase costs, emissions, and therefore 

emissions reductions. The cost-effectiveness calculation accounts for scaling of facilities and 

emissions, thus minimizing the impact on the cost effectiveness when increasing facility size. As 

shown in the following example, the throughput cancels out in the cost effectiveness 

calculation. 

|

$

=

$

× × ×

hh

× hh

|

Rule 4565 Composting-Related Emissions 

To estimate emissions reductions from Rule 4565, the District used estimates of emissions from 

the VOC sources. The composting mitigation measures used in the rule focus on the following 

three primary emission sources at biosolids composting facilities: (a) receiving/mixing areas, (b) 

active-phase compost piles, and (c) curing-phase compost piles. The District calculated 

emissions, based on the most recent data available, as follows: 

Composting Emissions 

Emissions Areas 

Small Facility 

(ton-VOC/yr) 

Medium Facility 

(ton-VOC/yr) 

Large Facility 

(ton-VOC/yr) 

Scraping Areas (Receiving/Mixing Areas) 1.27 6.36 12.72 

Active Piles 8.01 40.05 80.1 

Curing Piles 0.89 4.45 8.9 

Active+Curing Total 8.9 44.5 89.0 

The following discussion identifies the assumptions and calculations associated with the 

identified compost emission sources: 
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a) Receiving and Mixing (Scraping) Area Emissions 

At a composting facility, compostable material is delivered, dumped, mixed, and then 

transferred to the controlled processing piles; either windrows or engineered systems. 

During these steps, the compostable material is emitting VOCs, which can be reduced by 

scraping or sweeping the receiving/mixing area on a regular basis (Class One Mitigation 

Measure #1). The emissions during this process equate to emissions released during the 

active phase of composting, but are limited to the number of hours before the material 

is transferred, and based on the following assumptions: 

1. The VOC emission factor (EF) of 0.000424 lb-VOC/ton-hr, also a conservative value, 

is based on flux chamber source testing results from uncontrolled active-phase cocomposting as determined by Schmidt and Card (2002, 2004).1

 

2. Total emissions are based on the annual throughput of the facility, assuming that all 

compostable material (throughput) sits in the scraping area for 2 hours per day, 6 

days per week, and 50 weeks per year, for a total of 600 hours per year. 

The following example calculates the annual emissions attributable to the scraping area of a 

small facility: 

Example: 

 |

=

− h × hh ( ) × × ×

2000

1.27 =

0.000424 − h × 10,000( ) × 2 × 6 × 50

2000

b) Active-Phase and Curing-Phase Compost Emissions 

The District used South Coast Air Quality Management District’s Rule 1133.2 (Emission 

Reductions from Co-composting Operations) co-composting emission factor of 1.78 lbVOC/ton, which accounts for both the active and curing phases in combination. Based 

on a study prepared for the San Joaquin Valleywide Air Pollution Study Agency (2009),2

the emission factor is split 90%-10%, where 90% is attributed to the active phase and 

 

1 Card, T. and Schmidt, C. (2002). Emissions Evaluation of Aerated Static Pile Composting of Anaerobically Digested Biosolids 

at the Davenport Composting Facility (Draft Report). Prepared for Southern California Alliance of Publicly Owned Treatment 

Works and updated in 2004. 

2

 San Joaquin Valleywide Air Pollution Study Agency [SJVAPSA]. (Draft 2011). Comparison of Mitigation Measures for 

Reduction of Emissions Resulting from Greenwaste Composting. Fresno, CA: San Joaquin Valleywide Air Pollution Study 

Agency. Retrieved from website: 

http://www.valleyair.org/busind/pto/emission_factors/Criteria/Criteria/Composting/Compost%20Study%20Draft%20Report.pdf

(Draft Report) and 

http://www.valleyair.org/busind/pto/emission_factors/Criteria/Criteria/Composting/Compost%20Study%20Appendices.pdf

(Appendices) 
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10% to the curing phase. The following example shows the annual emissions occurring 

during the active phase at a medium compost facility: 

Example Active-Phase: 

 | −h

=

 × % h× hh

2000

40.05 =

1 .78 × 0.90 × 50,000

2000

Rule 4565 Control Measure Efficiencies 

The District based emissions reductions for Rule 4565 on the following control efficiencies for 

each mitigation measure: 

The District used data from the SJVAPSA (2011) study to update overall control efficiency for 

compost cover, but maintained efficiency values for scraping and the Class 2 measures that 

were used in the original 2006 rulemaking process and as used by SCAQMD for their Rule 

1133.2 (Emission Reductions from Co-composting Operations).

Class 1 Measures

Overall Control 

Efficiency

10%

56%

56%

Class 2 Measures

Overall Control 

Efficiency

26%

80%

26%

80%

ASPs + Compost Cover

Overall Control 

Efficiency

Active-Phase ASPs to ≥ 80% control + Compost Cover 64%

Curing-Phase ASPs to ≥ 80% control + Compost Cover 64%

Scrape to ≤ 1"

Cover Active Piles ≥ 6"

Cover Curing Piles ≥ 6"

Active-Phase ASPs to ≥ 80% control

Active-Phase in-vessel to ≥ 80% control

Curing-Phase ASPs to ≥ 80% control

Curing-Phase in-vessel to ≥ 80% control
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a) Control Efficiencies for Class 1 Mitigation Measures 

1) Scraping: The 10% control efficiency assumption for scraping is conservatively 

high since the entire class one category menu of control options was estimated 

to be 10% total if all the measures were combined. 

2) Compost Cover: The District derived an emissions profile from SJVAPSA (2011) 

that indicates 56% control efficiency for the active phase of composting. Given 

the use of the same type of compost cover and the nature of the emissions, the 

District also estimates 56% control efficiency for compost cover during the curing 

phase. 

b) Control Efficiencies for Class 2 Mitigation Measures 

1) Active and curing-phase aerated static pile systems (ASPs) to 80% Control: Rule 

4565 conservatively assumes a 33% capture efficiency for an aerated static pile 

system. Applying an 80% control to the captured emissions results in a 26% 

overall VOC control, as shown below: 

Overall Control: 0.33 x 0.8 x 100 = 26% 

2) In-vessel active- and curing-phase to 80% control: The in-vessel engineered 

systems can be designed for 100% capture of the emissions. Applying 80% 

control to 100% capture results in 80% overall VOC control. 

3) ASPs plus compost cover: Alternatively, a facility may choose to use ASPs to 80% 

control plus a compost cover. As mentioned for ASPs, the overall control is 26%. 

When the compost cover control of 56% is attributed to the un-captured ASP 

emissions, the result is 64% overall control, as shown below: 

Overall Control: 0.26 + [(1 - 0.33) x (0.56)] x 100 = 64% 

Rule 4565 Emissions Reductions 

Using the calculated emissions, as shown in “Rule 4565 Composting-Related Emissions” 

(above), and the control efficiency shown in “Rule 4565 Control Measure Efficiencies” (in the 

previous section), the District calculated the emissions reductions for each mitigation measure 

and each size facility. 
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 Emissions Reductions 

Class 1 Measures 

Overall 

Control 

Efficiency 

Small Facility 

(ton-VOC/yr) 

Medium Facility 

(ton-VOC/yr) 

Large Facility 

(ton-VOC/yr) 

Scrape to ≤ 1" 10% 0.1 0.6 1.3 

Cover Active Piles ≥ 6" 56% 4.5 22.4 44.9 

Cover Curing Piles ≥ 6" 56% 0.5 2.5 5.0 

Class 2 Measures 

Overall 

Control 

Efficiency 

Small Facility 

(ton-VOC/yr) 

Medium Facility 

(ton-VOC/yr) 

Large Facility 

(ton-VOC/yr) 

Active-Phase ASPs to ≥ 80% control 26% 2.1 10.6 21.1 

Active-Phase in-vessel to ≥ 80% control 80% 6.4 32.0 64.1 

Curing-Phase ASPs to ≥ 80% control 26% 0.2 1.2 2.3 

Curing-Phase in-vessel to ≥ 80% control 80% 0.7 3.6 7.1 

ASPs + Compost Cover 

Overall 

Control 

Efficiency 

Small Facility 

(ton-VOC/yr) 

Medium Facility 

(ton-VOC/yr) 

Large Facility 

(ton-VOC/yr) 

Active-Phase ASPs to ≥ 80% control + Compost 

Cover 

64% 5.1 25.6 51.2 

Curing-Phase ASPs to ≥ 80% control + Compost 

Cover 

64% 0.6 2.8 5.7 

The following examples demonstrate the emissions reduction calculation for a small and 

medium facility: 

Examples: 

( | )

= ( | ) × (%)

0.127 = 1.27 × 0.10

( | )

= ( | ) × 

 

(%)

22.4 = 40.05 × 0.56

Rule 4565 Cost of Reductions to a Facility 

The table below summarizes the cost of Class One and Class Two compost mitigation measures, 

except for the those Class One mitigation measures deemed as best management practices 

(Oxygen content, moisture content, and C:N ratio; class one mitigation measure 2, 3, and 4, 

respectively), which are inherent to producing compost. The District has updated the costs 

since the 2006 rulemaking to account for information, data, and estimates acquired during 

2010 and 2011 in preparation for Rule 4566 (Organic Material Composting Operations), and as 

referenced previously in this document. 
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a) Cost of Class One Measures 

1) Scraping: The scraping cost conservatively includes labor and maintenance only. 

The District assumed that the facility would use existing equipment, such as 

existing front-end loaders, to perform the scraping. The analysis assumes a $100 

per hour labor cost plus equipment overhead and maintenance, based on 

conversation with a Valley greenwaste facility operator in 2011. The analysis 

also assumes it takes approximately 1 to 2 hours to completely scrape and move 

the material from the scraping area to the controlled locations for compost 

processing. Additionally, costs for the medium and large facilities assume that 

operators must scrape and travel twice and four times, respectively, as much 

compared to small facilities. The dollars-per-year cost was then divided by the 

annual throughput to result in a dollars-per-ton cost to the facility, as shown in 

the following example: 

Example:

 |

$

=

 |

$

× × ×

hh

3.00

$

=

100.00 $× 1 × 6 × 50

10,000

2) Compost Cover: The District based the cost of the compost cover on extensive 

research from the greenwaste industry during the development of District Rule 

4566 (Organic Material Composting Operations). During 2010 and 2011, the 

District obtained estimates from SJV greenwaste facility operators on the costs 

to implement the compost cover at their existing greenwaste windrow 

composting facilities. The cost includes capital costs, annualized at 10% over 10 

years, plus ongoing annual costs. The capital investments include additional 

front-end loaders and dump trucks. The ongoing costs included additional labor, 

overhead, and heavy equipment operation and maintenance. The costs were 

Class 1 Measures

3.00 6.00 1.20 2.40 1.20 2.40

7.88 10.81 7.88 8.85 3.33 3.53

7.88 10.81 7.88 8.85 3.33 3.53

Class 2 Measures

Active-Phase in-vessel to ≥ 80% control 

Curing-Phase in-vessel to ≥ 80% control

Active-Phase ASPs to ≥ 80% control 

Curing-Phase ASPs to ≥ 80% control 

Large Facility Cost Range 

($/ton-compost)

Cost to Facility

Small Facility Cost Range 

($/ton-compost)

Medium Facility Cost Range 

($/ton-compost)

Large Facility Cost Range 

($/ton-compost)

Small Facility Cost Range 

($/ton-compost)

Medium Facility Cost Range 

($/ton-compost)

Scrape to ≤ 1"

Cover Active Piles ≥ 6" 

Cover Curing Piles ≥ 6"

15.25

10.80 13.58 9.60 10.50 7.40 9.15

18.00 22.63 16.00 17.50 12.34
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obtained for the active phase only; however, the same costs are applied to the 

curing phase for this analysis. The same cost for the curing phase is considered 

conservative since there is typically twice as many curing piles than active piles 

at a compost facility. The dollar-per-year cost was then divided by the annual 

throughput to result in a dollars-per-ton cost to the facility. 

b) Cost of Class Two Measures 

1) In-vessel active and curing phase to 80% control: The costs for engineered invessel controls reflect extensive research done by the District during the 

development of District Rule 4566 during 2010 and 2011. These costs are all 

proprietary vendor quotes for hypothetical SJV greenwaste sites of various sizes. 

The vendors who provided data are Engineered Compost Systems (ECS), W.L. 

Gore & Associates (GORE), and Managed Organic Recycling (MOR). The 

engineered in-vessel systems include ASPs with covers on each pile. The vendors 

estimated costs based on the concept of converting an existing facility to an invessel facility and included capital and installation costs annualized at 10% over 

10 years, plus ongoing annual costs. Capital costs primarily include aerated grid, 

ducting, cover, associated blowers, biofilters, and cover winders. A primary 

conservative assumption is that the sites are ready, buildable dirt slabs. Primary 

ongoing costs include operations labor, electric power, cover-winder fuel, and 

general maintenance 

The vendors provided cost ranges based on options available to operators; one 

site may be able to use less equipment while another may need or want more, 

such as concrete slabs and push walls. It is important to note that in-vessel 

systems involve ASPs with covers, so no turning of the windrows is required. As 

such, the cost of windrow turners and the associated O&M are not included 

here. 

2) Active- and curing-phase ASPs to 80% control: The difference between the invessel systems and the ASPs is the use of a cover for the in-vessel systems. The 

analysis assumes that the cover and associated equipment, e.g. cover winder, 

conservatively consist of 50% of the initial and ongoing costs. As such, the ASP 

costs are half the in-vessel costs. By overstating the cover costs, the ASP option 

becomes more cost-effective. 
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Rule 4565 Compost Mitigation Measure Cost Effectiveness 

The tables below summarize the cost effectiveness of the class one and class two mitigation 

measures, except for the BMPs, which are inherent to producing compost. Note that the costeffectiveness results reflect recent information on emissions, controls, and new and more 

accurate cost data, which are different than the original 2006 rulemaking values. 

The following example demonstrates the cost effective calculation: 

Example: 

 |

$

= 

 |

$

× hh

 |

235,849 

$

= 

3.00 $

× 10,000 

. 1272 

Class 1 Measures

 235,849 471,698 94,340 188,679 94,340 188,679

 17,567 24,099 17,567 19,730

 158,106 216,894 158,106 177,568

Scrape to ≤ 1"

Cover Active Piles ≥ 6"

Cover Curing Piles ≥ 6" 

See Alt. Scenario Tables Below

Cost Effectiveness - Class 1 Measures

Small Facility Cost Range ($/tonVOCreduced)Medium Facility Cost Range 

($/ton-VOCreduced)

Large Facility Cost Range 

($/ton-VOCreduced)

Class 2 Measures

Active-Phase in-vessel to ≥ 80% control 

Curing-Phase in-vessel to ≥ 80% control

Active-Phase ASPs to ≥ 80% control 

Curing-Phase ASPs to ≥ 80% control 

Cost Effectiveness - Class 2 Measures

Large Facility Cost Range 

($/ton-VOCreduced)

 21,419

 31,512 38,943

 17,331

Alternative Scenario

Curing-Phase Compost Cover + ASPs to ≥

80% control

Cost Effectiveness - Compost Cover Both Phases + ASPs

Large Facility Cost Range 

($/ton-VOCreduced)

Active-Phase Compost Cover + ASPs to ≥

80% control

 24,722 28,494

Alternative Scenario

Cost Effectiveness - Compost Cover Active-Phase Only + ASPs

Large Facility Cost Range 

($/ton-VOCreduced)

Active-Phase Compost Cover + ASPs to ≥

80% control 20,045 23,679

Curing-Phase ASPs to ≥ 80% control