Document ID: EPA-HQ-RCRA-2008-0329-0238
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2009-01-02T05:00Z

Materials Characterization Paper

In Support of the 

Advanced Notice of Proposed Rulemaking – 

Identification of Nonhazardous Materials That Are Solid Waste

Biomass - Animal Manure and Gaseous Fuels

December 16, 2008

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

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

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

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).

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).

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).

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

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).

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).

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.

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 

Commodity	Annual Quantity Generated 	Annual Quantity Used as Fuel
Additional Annual Quantity 	Annual Quantity in Other Uses	Total Quantity
Stockpiled as of 2008

Cement Kilns	Other

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

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).

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.

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).

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.

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 then (DOE 2006).  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

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).

Impacts of Animal Manure and Gaseous Fuels Use:

Benefits include 1) energy use of methane, otherwise released to the
atmosphere (EPA 2008e), 2) displacement of fossil fuel, 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 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). 

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.

Exhibit 2:  Comparative Emissions of Biogas and Natural Gas Combustion 

Pollutant	Biogas	Natural Gas

	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

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

	

References

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 Biomass production estimates are presented on an annual basis.

 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”.

Biomass - Animal Manure and Gaseous Fuels

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