Materials Characterization Paper 

In Support of the 

Proposed Rulemaking – 

Identification of Nonhazardous Secondary Materials That Are Solid Waste 

Biomass - Animal Manure and Gaseous Fuels

March 18, 2010 

===================================================================== 

1. Definitions of Animal Manure and Gaseous Fuels 

In this context, we are defining animal manure as the excrement of livestock reared in 

agricultural operations as well as straw, sawdust, and other residues used as animal bedding. 

Gaseous fuels may be derived from municipal and industrial landfills (landfill gas) or from 

animal manure and solid biomass such as crop silage or the organic fraction of MSW (biogas). 

Both landfill gas and biogas are generated via anaerobic digestion, a multi-stage process whereby 

bacteria convert carbohydrates, fats, and proteins to methane (Evans 2001). EPA does not 

consider these materials to be wastes in themselves, when used as fuel, but rather materials 

derived from wastes. 

2. Annual Quantities of Animal Manure and Gaseous Fuels Generated and Used 

(1) Sectors that Generate Animal Manure and Gaseous Fuels: 

• NAICS 1121: Cattle Ranching and Farming 

• NAICS 1122: Hog and Pig Farming 

• NAICS 1123: Poultry and Egg Production 

• NAICS 1124: Sheep and Goat Farming 

• NAICS 112920: Horses and Other Equine Production 

• NAICS 562212: Solid Waste Landfill 

• NAICS 221320: Sewage Treatment Facilities 

(2) Quantities and Prices of Animal Manure and Gaseous Fuels Generated: 

• Domestic livestock production generates over a billion tons of manure annually. 

If all of this were used to produce biogas, it would yield approximately 19.4 

million tons of methane (Cuéllar and Webber 2008).1

• Anaerobic digestion of current manure production managed in ponds, anaerobic 

lagoons, and holding tanks would yield 2.4 million tons of methane. Current 

production is 0.07 million tons from 111 operating digesters (EPA 2008a). 

• Around 35 million dry tons of current manure production could be used for 

bioenergy purposes once sustainability concerns are met (e.g., this manure is 

available after primary use of manure on soils to maintain fertility) (Perlack et al. 

2005). 

 1

 Biomass production estimates are presented on an annual basis. 
Biomass - Animal Manure and Gaseous Fuels 

• In 2006, 11.4 million tons of landfill gas (3.0 million tons of methane) provided 

the equivalent of 150 trillion Btus for heat and electicity generation (EIA 2008). 

• Current landfill gas production from 455 operational projects is 3.6 million tons 

of methane (EPA 2008b). 

• A 2007 survey of anaerobic digestion systems at livestock facilities found an 

average biogas production cost of $6.60 per million btu (NRCS 2007). 

• Poultry litter sold for electricity generation at the Fibrominn LLC plant in Benson, 

MN, is purchased by contract with farmers at $3 to $5 per ton. The power helps 

meet a Minnesota legislative mandate for power generation from biomass, 

although it is not competitive with fossil fuels (Karnowski 2007). 

(3) Trends in Generation of Animal Manure and Gaseous Fuels:

• Livestock production has become increasingly concentrated in recent years 

(Kellogg et al. 2000). This facilitates the collection of secondary materials for 

bioenergy purposes. 

• Opportunities for utilizing animal byproducts for bioenergy production may 

increase in coming years with higher fossil fuel prices and improved conversion 

technologies including both biochemical and thermochemical platforms (Cantrell 

et al. 2008). 

3. Uses of Animal Manure and Gaseous Fuels 

(1) Combustion Uses of Animal Manure and Gaseous Fuels: 

• Biogas produced on farms is typically used to heat water for purposes of cleaning 

and sanitizing milking pipelines and equipment in dairy operations (NRCS 2007). 

Note that this biogas is derived from animal products, and is not an animal 

product itself. 

• An emerging market for animal manure is direct production of heat and power 

(e.g., the 55 megawatt Fibrominn LLC plant). 

• In 2006, landfill gas was used by the following sectors (energy basis): commercial 

(2.7 percent), industrial (49.3 percent), electric utilities (5.3 percent), and 

independent power producers (42.7 percent) (EIA 2008). 

• The combustor survey database developed by EPA for the 2009 proposal of the 

Commercial and Industrial Solid Waste Incinerator (CISWI) standards and the 

Industrial Boilers Maximum Achievable Control Technology (MACT) standards 

includes one combustion unit that reported using approximately 416,000 tons of 

manure as fuel (EPA 2009).2,3 The information in the database also indicates that 

units affected by these standards annually combust approximately 193,000 tons of 

 2

 Although we report mature quantities from the combustion database as a tonnage, the database includes 

material quantities expressed in terms of heating values (Btu). To express this information as a tonnage, we 

assumed that manure has a heating value of 6,187 Btu per pound, which is the thermal value for chicken litter 

reported by Wright (Wright et al. 2006). 

3

 The categories of material in the combustion database that we assume are manure are (1) poultry litter 

and (2) manure. 

2
Biomass - Animal Manure and Gaseous Fuels 

biogas and 3.4 million tons of material described in general terms as biomass or 

bio-liquids.4

 

(2) Non-Combustion Uses of Animal Manure and Gaseous Fuels:

• Animal manure is spread on cropland and pastureland as a fertilizer to replenish 

nutrients and as a soil treatment to improve soil quality by enhancing soil 

structure and increasing the soil’s ability to hold water and resist compaction 

(Kellogg et al. 2000). Other uses are uncommon in the US (e.g., home heating, 

cooking, and paper production). 

(3) Quantities of Animal Manure and Gaseous Fuels Landfilled: 

• The amount of animal manure landfilled has not been identified. 

• An additional 535 candidate landfills have been identified with the potential to 

provide 2.4 million tons of methane (EPA 2008b). Milbrandt (2005) estimated 

total domestic production from landfills and domestic wastewater treatment sites 

at 13.6 and 0.5 million tons of methane, respectively. 

(4) Quantities of Animal Manure and Gaseous Fuels Stockpiled/Stored:

• Information about quantities of animal manure stockpiled are unknown. While 

the quantity of animal manure undergoing short-term storage is significant, decay 

rates and issues associated with storage (leaks and odor), along with technical 

limitations associated with storage of gases likely place some limits on 

stockpiling activity, particularly because the value of these materials is not likely 

to appreciate as the result of long-term stockpiling. 

Exhibit 1: Overview of Generation and Use of Animal Manure and Gaseous Fuels 

Annual Quantity Used 

as Fuel Annual 

Quantity 

Generated 

Cement 

Kilns Other 

Additional 

Annual 

Quantity 

Annual 

Quantity in 

Other Uses 

Total 

Quantity 

Stockpiled as 

of 2008 

Commodity 

----------- million tons of methane per year -----------

Biogas from 

Agricultural 

Anaerobic 

Digesters 0.07 N/I 0.07 N/I N/I N/I 

Landfill Gas 3.60 N/I 3.60 2.4 – 10.0 N/I N/I 

N/I = not identified 

 4 To convert the total Btu values reported for biogas to a tonnage, we assumed a thermal value of 11,820 

Btu/lb (EIA 2008). To convert the total Btu values reported for general biomass and bio-liquids to tonnages, we 

assumed a thermal value of 6,000 Btu/lb for this material, based on the range of thermal values reported for biomass 

materials in this paper, the food scraps and agricultural residue materials characterization paper, and the materials 

characterization paper for forest derived biomass and pulp and paper residues.

3
Biomass - Animal Manure and Gaseous Fuels 

4. Management and Combustion Processes for Animal Manure and Gaseous Fuels 

(1) Types of Units Using Animal Manure and Gaseous Fuels:

• Biogas generated on farms is typically combusted directly in boilers and to a 

lesser extent is burned for space heating (NRCS 2007). 

• Landfill gas is used to generate electricity in internal combustion engines, gas 

turbines, and microturbines. It also has direct use applications in boilers, 

combined heat and power systems, dryers, kilns, and greenhouses (EPA 2008d). 

(2) Sourcing of Animal Manure and Gaseous Fuels:

• Manure is generated in all livestock operations. Anaerobic digesters for biogas 

production accommodate manure handled as a liquid, slurry, or semi-solid (i.e., 

total solids up to approximately 12 percent) (EPA 2002). 

• Landfill gas forms as a by-product of manure decomposition. 

(3) Processing of Animal Manure and Gaseous Fuels: 

• Biogas generated on farms is typically combusted on-site with little upgrading 

other than hydrogen sulfide and moisture removal. Carbon dioxide may also be 

removed for applications where high thermal values are needed (NRCS 2007). 

• Landfill gas also needs to undergo minimal upgrading when used in most 

applications (EPA 2000). Substantial upgrading is needed, however, should 

landfill gas be introduced into natural gas distribution networks. Here a series of 

membrane separation processes, molecular sieves, and absorption processes are 

employed (CCTP 2005). 

• Public comments submitted to EPA in response to the Advanced Notice of 

Proposed Rulemaking (ANPRM) suggest that manure is not typically treated to 

eliminate potentially harmful components before being applied to crop fields or 

stored (Werber 2009). 

(4) State Status of Animal Manure and Gaseous Fuels: 

• At this stage, we have not identified any states that have specifically granted a 

beneficial use designation for the use of animal manure as fuel, but we have not 

performed an exhaustive investigation of state activities and regulations. For 

example, it is possible that equivalent designations are made by states as part of 

agricultural regulation.5

• As of September 2006, approximately 50 percent of states had renewable fuels 

portfolio standards requiring that varying percentages of power generated within 

the individual states come from alternative fuels (including biomass) by a 

designated future date; several more states have enacted such regulations since 

 5

 Although we identified no states with a beneficial use designation for the use of animal manure as a fuel, 

public comments submitted in response to the ANPRM indicate that there are ongoing studies to determine the 

feasibility of using animal waste product, specifically chicken manure or “chicken litter” as a fuel for cement kilns 

(Elliott 2009). 

4
Biomass - Animal Manure and Gaseous Fuels 

then (DOE 2006).6 For instance, in August 2007, North Carolina enacted a law to 

“promote the development or renewable energy...through implementation of a 

renewable energy and energy efficiency portfolio standard (REPS)” (Session Law 

2007-397. This law specifically calls for the following: 

Sec. 62-133.7 (e). Compliance with REPS requirement through 

use of swine waste resources. -- For calendar year 2018 and for 

each calendar year thereafter, at least two-tenths of one percent 

(0.2%) of the total electric power in kilowatt hours sold to retail 

electric customers in the State shall be supplied, or contracted for 

supply in each year, by swine waste. [Interim percentages are 

mandated for 2012 and 2015.] 

Sec 62.133.7(f). Compliance with REPS requirement through use 

of poultry waste resources. -- For calendar year 2014 and for each 

calendar year thereafter, at least 900,000 megawatt hours of the 

total electric power sold to retail electric customers in the State 

shall be supplied, or contracted for supply in each year, by poultry 

waste combined with wood shavings, rice hulls, or other bedding 

material. [Interim megawatt hour values are mandated for 2012 

and 2013.] 

5. Animal Manure and Gaseous Fuels Composition and Impacts 

(1) Composition of Animal Manure and Gaseous Fuels:

• Biogas from on-farm anaerobic digesters typically contains 60 to 70 percent 

methane and 30 to 40 percent carbon dioxide by volume (NRCS 2007). Landfill 

gas tends to contain between 45 to 55 percent methane and 45 to 55 percent 

carbon dioxide (Messics 2001). Average low heat values of gaseous fuels are 

approximately 19,840 btu/lb for methane, 11,820 for biogas, and 6,500 for landfill 

gas (EIA 2008). 

• Poultry litter has a high heat value of 6,187 btu/lb (Wright et al. 2006). 

• Public comments submitted by the Environmental Integrity Project in response to 

the ANPRM maintain that all concentrated animal feeding operations (CAFO) 

waste contains heavy metals, halogens, dioxins, and other hazardous compounds 

(Werber 2009). 

 6 The summary table in the reference does not always specify which types of biomass are included, 

however, some examples specific to animal manure and gaseous fuels include: Maryland specifies “poultry litter 

incineration”; Nevada specifies “biomass (includes...animal waste...)”; and New Mexico specifies “animal waste” in 

the definition of “biomass resources”. Other states use the term “sustainable biomass” which could include animal 

manure/gaseous fuels, while others may include animal manure/gaseous fuels in the generic term “biomass”.

5
Biomass - Animal Manure and Gaseous Fuels 

(2) Impacts of Animal Manure and Gaseous Fuels Use:

• Benefits include 1) energy use of methane, a greenhouse gas, otherwise released 

to the atmosphere (EPA 2008e), 2) displacement of fossil fuels, primarily natural 

gas, and, 3) potential reduction of pollutants harmful to human health (NRC 

2003). 

• Landfill gas emissions vary considerably depending on the composition of the 

waste in the landfill, the efficiency with which gas is captured, and the pollution 

control technologies used in combustion. Combustion of landfill gas for energy 

leads to reductions in greenhouse gases, VOCs, and organic mercury compounds 

relative to uncontrolled emissions from landfills (EPA 2008f). In addition, 

combustion of landfill gas avoids the impacts associated with extraction, 

processing, and transportation of typical primary fuels like natural gas. The 

emissions and upstream impacts associated with natural gas combustion are 

identified in Exhibit 2. 

• Fermentation of pig manure to create biogas has been shown to reduce nitrous 

oxide by 14 grams per ton of manure compared to typical storage and fertilizer 

applications (Nielsen 2002). 

• In addition to the avoided GHG emissions, combustion of biogas as a replacement 

for natural gas avoids the emissions associated with the extraction and processing 

of natural gas. Exhibit 2 lists the emissions from combustion of biogas from a 

typical pig farm and combustion and pre-combustion processing of natural gas at 

a typical industrial boiler in the U.S. in the late 1990s. Note that the emissions of 

many of the criteria pollutants are similar to natural gas combustion, but 

significant reductions are achieved by avoiding the impacts associated with 

extraction and processing of natural gas. 

6
Biomass - Animal Manure and Gaseous Fuels 

Exhibit 2: Comparative Emissions of Biogas and Natural Gas Combustion 

Biogas Natural Gas 

Pollutant Combustion Combustion Combustion plus Upstream 

----- Lb./MMBtu -----

Criteria Pollutants 

PM2.5 0.003 - - 

PM10 0.003 0.009 0.009 

PM, unspecified - - 0.004 

NOx 0.072 0.301 0.417 

VOCs 0.009 0.009 0.524 

SOx 0.026 0.073 1.985 

CO 0.084 0.058 0.282 

Pb - - 2.72x10-7

Hg - - 7.18x10-8

Greenhouse Gases

CO2 194.5 114.6 129.8 

CH4 0.009 0.003 0.372 

N2O 0.005 - 1.17x10-5

MTCO2E/MMBtu 0.089 0.052 0.062

Sources:

Franklin Associates 1998; Nielson 2002. 

Notes:

“-” signifies data not available; may equal zero. Emissions of biogas reflect combustion 

process only and do not include upstream, downstream, or avoided impacts. 

The emission information presented in this table is derived from Life Cycle Inventory 

(LCI) data, as compiled by Franklin Associates. LCI data identifies and quantifies 

resource inputs, energy requirements, and releases to the air, water, and land for each step 

in the manufacture of a product or process, from the extraction of the raw materials to 

ultimate disposal. The LCI can be used to identify those system components or life cycle 

steps that are the main contributors to environmental burdens such as energy use, solid 

waste, and atmospheric and waterborne emissions. Uncertainty in an LCI is due to the 

cumulative effects of input uncertainties and data variability. 

There are several life cycle inventory databases available in the U.S. and Europe. For this 

paper, we applied the most readily available LCI database that was most consistent with 

the materials and uses examined. These LCI data rely on system boundaries as defined by 

Franklin Associates, as described in the documentation for this database, available at: 

http://www.pre.nl/download/manuals/DatabaseManualFranklinUS98.pdf. 

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Biomass - Animal Manure and Gaseous Fuels 

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