United States

Department 

of Agriculture

Economic 

Research 

Service

June 2009

Manure Use for Fertilizer

and for Energy

Report to Congress
The report was prepared by James M. MacDonald, Marc O. 

Ribaudo, Michael J. Livingston, Jayson Beckman, and Wen Huang, 

Economic Research Service, U.S. Department of Agriculture.
United States 

Department 

of Agriculture 

Abstract

The Food, Conservation, and Energy Act of 2008 directed the U.S. Department of 

Agriculture to evaluate the role of animal manure as a source of fertilizer, and its other 

uses. About 5 percent of all U.S. cropland is currently fertilized with livestock manure, 

and corn accounts for over half of the acreage to which manure is applied. Expanded 

environmental regulation through nutrient management plans will likely lead to wider 

use of manure on cropland, at higher production costs, but with only modest impacts on 

production costs, commodity demand, or farm structure. There is widespread interest in 

using manure as a feedstock for energy production. While current use is quite limited, 

expanded government support, either direct or indirectly, could lead to a substantial 

increase in manure use as a feedstock. However, current energy processes are unlikely to 

compete with fertilizer uses of manure, because they leave fertilizer nutrients as residues, 

in more marketable form, and because manure-to-energy projects will be most profi table 

in regions where raw manure is in excess supply, with the least value as fertilizer.

Acknowledgments

We received helpful comments and advice from Carolyn Leibrand and Tony Crooks from 

USDA Rural Development; Mark Peters, Noel Gollehon, Glenn Carpenter, and William 

Boyd from the USDA Natural Resources Conservation Service; Bill McBride from the 

USDA Economic Research Service; Ray Massey from the University of Missouri; Wendy 

Powers and Dale Rozeboom from Michigan State University; and Roselina Angel from 

the University of Maryland.

Report to Congress

Manure Use for Fertilizer 

and for Energy

June 2009
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Manure Use for Fertilizer and for Energy / Report to Congress

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Table of Contents

Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

 Data Sources for this Study. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

 Linkages Among Livestock, Manure Production, and Crop Needs . . . . 3

 Dairy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

 Hogs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

 Broilers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

 Fed Cattle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Use of Manure as a Crop Fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

 Manure Use in the Aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

 Which Farmers Use Manure? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

 Manure Transport Among Farms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

 Substitution Between Manure and Commercial Nitrogen Applications 15

 Methods of Manure Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Impacts on Animal Operations of Restricting Manure Applications . . 18

 Hogs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

 Dairy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Competition from Energy Uses of Manure . . . . . . . . . . . . . . . . . . . . . . 32

 Manure to Energy Systems in Current Commercial Use . . . . . . . . . . . 32

 Extent of Current Adoption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

 Drivers of Adoption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

 Impacts on Fertilizer Uses for Manure . . . . . . . . . . . . . . . . . . . . . . . . . 39

Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

 Extent to which Animal Manure is Used as a Fertilizer. . . . . . . . . . . . . 41

 Potential Impact from Limitations Placed on Use of Animal Manure . . 41

 Effects on Agricultural Production due to Increased Competition 

 for Manure for Energy Production . . . . . . . . . . . . . . . . . . . . . . . . . . 42

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Glossary of Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
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Summary

Animal manure can be used as a fertilizer, and it can improve soil quality. 

Manure can also be used as a feedstock for energy production. But excessive 

concentrations of manure, either in storage or in land application, can create 

environmental risks, and farmers are facing increased regulation of their 

manure management practices. 

What Is the Issue?

The Food, Conservation, and Energy Act of 2008 directed the Department of 

Agriculture (USDA) to prepare a study that would evaluate the role of animal 

manure as a source of fertilizer, and its other uses. The study was to provide: 

1. a determination of the extent to which animal manure is utilized as 

fertilizer in agricultural operations by type (including species and 

agronomic practices employed) and size;

2. an evaluation of the potential impact on consumers and on 

agricultural operations (by size) resulting from limitations being 

placed on the utilization of animal manure as fertilizer; 

and

3. an evaluation of the effects on agriculture production contributable 

to the increased competition for animal manure use due to 

bioenergy production, including as a feedstock or a replacement for 

fossil fuels.

Animal manure is used as a crop fertilizer and soil amendment, but it can 

pose environmental risks when stockpiled or applied in excessive amounts. 

Federal, State, and local governments have responded to the environmental 

risks with regulations and conservation programs, and some State and 

local governments have also initiated lawsuits against livestock operations, 

claiming damages to water resources from manure. Efforts to comply with 

regulations impose costs on certain livestock operations and will likely lead 

to changes in manure use on those operations. 

There is also increasing interest in using manure for energy production. 

Methane can be captured from the biogas in manure and burned for 

electricity generation, while manure can also be burned directly as a 

feedstock in combustion processes. This report assesses current patterns 

of use of manure as fertilizer and evaluates the likely impacts of emerging 

environmental regulations on manure use. The report also assesses current 

efforts to use manure for energy production and evaluates the impact of 

bioenergy investments on manure’s use as fertilizer.

What Did the Study Find?

About 15.8 million acres of cropland, equivalent to about 5 percent of all 

U.S. cropland, are fertilized with livestock manure. Corn, which is planted 

on about one-quarter of U.S. cropland, accounts for over half of the land 

receiving manure. Patterns of manure use are driven by the agronomic needs 

of crops and by transport costs, which limit the distance that manure can be 
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moved and create close links between types of livestock and certain crop 

commodities. Each favors the application of manure to corn.

Most manure applied to corn comes from dairy and hog operations. Manure 

from poultry and cattle feedlot operations is drier and less costly to transport, 

and is therefore often removed from the farm and shipped to other operations. 

Because broiler production is concentrated in the southern United States, 

crops like peanuts and cotton rely heavily on broiler manure when they use 

manure fertilizers.

Large livestock operations are increasingly required to have nutrient 

management plans, which require balancing nutrient applications with the 

nutrient utilization of crops. Compliance with the plans can raise farm 

costs. Estimated costs vary sharply with the degree to which excess manure 

needs to be disposed of and the willingness of nearby farmers to accept 

manure for application to their cropland. A low willingness to accept among 

nearby farmers means that livestock producers will need to transport excess 

manure much farther for crop application. With a limited willingness to 

accept manure (defi ned as 20 percent of nearby farmers), we estimated that 

production costs, including those for manure management, would likely rise 

by 2.5-3.5 percent for large operations. 

Such increases are unlikely to alter the emerging structure of livestock 

production, where large operations have substantial cost advantages over 

small operations. They are also unlikely to lead to substantial declines in 

production and consumption; the resulting percentage retail price changes 

would be less than the cost changes noted above because farm costs are only 

a fraction of retail costs, and retail demand for meat and milk is relatively 

insensitive to price changes. As a result, expanded regulation through nutrient 

management plans will likely lead to wider use of manure on cropland, at 

higher production costs, with little impact on the size structure of farming 

operations. 

Manure-to-energy projects are not currently in widespread use. Digester 

systems, including those planned or in construction, cover less than 3 

percent of dairy cows and less than 1 percent of hogs. The single operating 

combustion plant utilizes litter from 6.6 percent of U.S. turkey production, 

while an idled plant in California could utilize manure from about 3 percent 

of fed cattle. 

Manure-to-energy projects may allow farmers to realize benefi ts from 

avoided purchases of electricity, from selling electricity, or from selling 

manure to generating plants, but few realize enough savings to justify the 

expense. But because such projects use existing resources, they could provide 

society with benefi ts if manure replaces newly mined fossil fuels in energy 

production, and if methane, a greenhouse gas, can be captured. Those 

societal benefi ts have led to proposals to support manure-to-energy projects 

through State utility mandates (to purchase electricity from farms and to 

invest in renewable production sites), through subsidies for capital costs, and 

through direct subsidies and credits for energy production. Expanded support 

could lead to a substantial growth of energy applications for manure. 
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Manure Use for Fertilizer and for Energy / Report to Congress

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Currently envisioned manure-to-energy projects are not likely to impose 

substantive constraints on the use of manure as fertilizer. Many of the 

nutrients that are benefi cial to crop growth remain after energy production. 

Nitrogen, phosphorus, and potassium nutrients remain in the effl uent of the 

digester process, to be spread on fi elds. Combustion processes do consume 

the nitrogen nutrients in manure, but leave phosphorus and potassium in an 

ash residue that, because of its concentrated form, is less costly to transport 

than raw manure. In addition, manure-to-energy projects function in markets 

for fertilizer and energy, and will be most economic in those areas in which 

the acquisition costs of manure are lowest. In turn, manure acquisition costs 

will be lowest where manure is in excess supply, with the least value as 

fertilizer.

How Was the Study Conducted?

The report relies primarily on a large-scale representative survey of farms, 

the annual Agricultural Resource Management Survey (ARMS), which is 

the USDA’s primary source of information on farm production practices 

and the fi nancial condition of farm businesses and households. One phase 

of the survey (Phase II) focuses on operations that produce specifi c crops, 

and includes questions concerning land use and production practices for the 

crop, including manure applications. Recent Phase II surveys covered barley 

(2003), corn (2005), cotton (2003), oats (2005), peanuts (2004), sorghum 

(2003), soybeans (2006), and wheat (2004), which allows us to assess manure 

use and management practices for those major fi eld crops. 

Another survey phase (Phase III) provides data on farm organization 

and structure for all commodities, and it also provides data on manure 

production and management practices on selected livestock operations. 

Commodities covered include hogs (1998 and 2004), dairy (2000 and 2005), 

and broilers (2006). We supplement ARMS with data from other USDA 

surveys, including the census of agriculture, as well as databases developed 

by the Environmental Protection Agency (EPA), USDA’s Natural Resources 

Conservation Service (NRCS), and the American Society of Agricultural and 

Biological Engineers (ASAE). 
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Introduction

The Food, Conservation, and Energy Act of 2008 (commonly known as the 

2008 Farm Bill) directed the Department of Agriculture (USDA) to prepare a 

study that would evaluate the role of animal manure as a source of fertilizer 

and other uses. Specifi cally, the statute (Title XI, Section 11014) called for a 

study to provide: 

1. a determination of the extent to which animal manure is utilized as 

fertilizer in agricultural operations by type (including species and 

agronomic practices employed) and size;

2. an evaluation of the potential impact on consumers and on agricultural 

operations (by size) resulting from limitations being placed on the 

utilization of animal manure as fertilizer; and

3. an evaluation of the effects on agriculture production contributable 

to the increased competition for animal manure use due to bioenergy 

production, including as a feedstock or a replacement for fossil fuels.

Manure is used widely as a crop fertilizer and as a soil amendment. It 

contains nutrients—such as nitrogen, phosphorus, and potassium—that 

facilitate plant growth, and manure can improve soil quality by neutralizing 

acidity, increasing organic matter, decreasing compaction, and increasing 

water-holding capacity. Manure can be deposited on cropland by grazing 

animals, but is commonly transported from animal confi nement and manure 

storage facilities and spread on the ground or injected into it. 

Manure is a substitute for commercial fertilizers, whose prices rose sharply 

in recent years along with prices for other products derived from fossil 

fuels and minerals (Huang, 2009). Nitrogenous commercial fertilizer prices 

doubled between 2000 and 2007, and then rose again by 62 percent between 

December of 2007 and September of 2008. Phosphatic commercial fertilizer 

prices rose by 115 percent between 2000 and 2007, and then rose by 177 

percent between December 2007, and September 2008.1 Prices for each 

receded to 2007 levels by the Winter of 2009, but the sharp price changes 

and likelihood of high future prices have kindled greater interest in manure 

fertilizers.

Higher commercial fertilizer prices make manure fertilizers look more 

attractive. However, opportunities for widespread manure substitution are 

limited: manure can be costly to transport for even short distances, and some 

crops are far from sources of manure production. Moreover, manure may not 

have the precise combination of nutrients needed for specifi c crops and fi elds. 

This report details current patterns of manure use on crops and identifi es 

factors that limit manure use.

Manure can also pose environmental and human health risks when stockpiled 

or applied in excessive amounts. Wastes can be transmitted from cropland to 

surface waters through the runoff of nutrients, organic matter, and pathogens 

from fi elds and storage; to ground water through the leaching of nutrients 

and pathogens; and to the atmosphere through the volatilization of gases 

and odors. Pollutants may originate at structures where animals are kept; at 

1U.S. Bureau of Labor Statistics, 

Producer Price Index 

(http://stats.bls.gov/ppi/#data).
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manure storage facilities such as tanks, ponds, or lagoons; or on land where 

manure is stored or is applied as fertilizer. 

Because industrialized livestock production concentrates manure on limited 

land areas, some producers apply manure at intensities well above the 

agronomic needs of crops, thereby increasing pollution risks. Most also store 

manure prior to application, in pits and lagoons, posing environmental risks 

from seepage, fl ooding, or catastrophic failure. Manure odor is a persistent 

local issue, leading to the use of setback rules separating animal operations 

from residential areas.

Federal, State, and local governments have responded to manure’s 

environmental risks with regulations and conservation programs. Federal 

and State regulatory initiatives require many large operations to develop and 

implement nutrient management plans (NMPs) that base nutrient applications 

on agronomic rates, and many operations will need to spread their manure 

over a much larger land base, or reduce manure production, in order to 

comply with their NMPs. 

Compliance with NMPs imposes costs on large confi ned livestock operations, 

and has led to changes in manure use and management practices on many 

operations. To the extent that rules force manure to be spread over a larger 

landbase, they also spur interest in improved transport and application 

of manure as a substitute for commercial fertilizers. This report assesses 

the likely costs of such regulatory initiatives, as well as the responses that 

producers are taking.

State and local governments have taken other steps aimed at controlling 

manure production and application. California has enacted regulations in 

the San Joaquin Valley to protect heavily populated areas downwind from 

animal feeding operations, and has required many feeding operations in the 

Valley to obtain permits for manure discharges. North Carolina imposed 

a partial moratorium in 1997 on the construction of new hog farms in the 

State. Urbanizing development in each State has led to increased regulation 

of livestock feeding operations, and has also led to rising land prices, which 

have induced some livestock feeding to move to less dense areas. 

Animal manure can also provide a source of fuel for heating and electricity 

generation. Dry manure has long provided heat and cooking fuel for rural 

societies, but the biogas from manure contains carbon dioxide and methane, 

greenhouse gases that remain in the atmosphere, trapping heat. Methane can 

be captured from biogas and burned for electricity generation (used on-farm 

or transmitted for use elsewhere through the electricity transmission grid), 

and it can be purifi ed to yield pipeline-quality natural gas. Manure can also 

be shipped to centralized conversion and/or generation facilities. Growing 

environmental concerns, as well as long-term price increases for electricity, 

have led to growing interest in the use of manure for energy production. This 

report assesses current efforts to use manure for energy production, describes 

the barriers to further adoption, and evaluates the impact of bioenergy uses 

on manure’s use as fertilizer.
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Data Sources for this Study

This report relies on a large-scale representative survey of producers, the 

annual Agricultural Resource Management Survey (ARMS), which is the 

USDA’s primary source of information on the fi nancial condition of farm 

businesses and households and farm production practices. ARMS consists 

of enumerator-assisted surveys of farm operators, focused on their farm 

business and household. Administered jointly by the Economic Research 

Service (ERS) and the National Agricultural Statistics Service (NASS), it 

is conducted annually in three phases. Phase I is a screening questionnaire 

used to improve survey effi ciency. Phase II, conducted during the fall of each 

year, aims at physical and economic data on production inputs, management 

practices, and commodity costs of production. Phase III, conducted in 

the winter following the reference year, focuses on farm income and 

expenditures, farm fi nancial arrangements, and other characteristics of the 

farm business and farm household.

The Phase II surveys focus on operations that produce specifi c crops; a fi eld 

planted to that crop is chosen at random for questions concerning land use 

and production practices, including manure applications. Phase II respondents 

also receive Phase III surveys, so the information on production practices 

can be linked to farm fi nancial information. Phase II covers 1-2 crops in 

most years, with recent surveys directed to barley (2003), corn (2005), cotton 

(2003), oats (2005), peanuts (2004), sorghum (2003), soybeans (2006), and 

wheat (2004), which allows ERS to assess manure applications to those major 

fi eld crops. The surveys are weighted so as to be nationally representative of 

each commodity.

Phase III surveys provide data on farm organization, fi nances, and marketing 

practices for all commodities (not just those covered in Phase II) and all 

farm types in the continental United States. Phase III usually contains 

several versions, with a commodity-specifi c livestock version in most years. 

Livestock versions elicit information on production and expenses, marketing 

and investment decisions, and production practices, including manure 

management decisions. Commodities covered include hogs (1998 and 2004), 

dairy (2000 and 2005), and broilers (2006).

ARMS data provide the primary source of information on manure production 

and use. We supplement ARMS with manure production estimates developed 

by the American Society of Agricultural and Biological Engineers and with 

livestock inventory and production data from other USDA surveys, including 

the census of agriculture. Large-scale USDA surveys do not yet provide 

reliable data on energy uses for manure.2 For that information, we turn to 

databases developed by the Environmental Protection Agency (EPA) and 

USDA’s Natural Resources Conservation Service (NRCS). 

Linkages Among Livestock, Manure Production, 

and Crop Needs

Manure use is infl uenced by the size, product mix, and location of crop and 

livestock farms. In this section, we describe these structural elements and 

their impact on manure utilization. 

2Given its current sample size, ARMS 

will not include activities with small 

numbers of participants, such as 

on-farm energy uses of manure (for 

example, only about 100 dairy farms, 

out of 70,000 nationwide, currently use 

anaerobic digesters).
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Commodity production is becoming more specialized. Many crop operations 

have no livestock, and therefore no on-farm manure production. Some 

livestock operations specialize only in livestock, and forgo crop production 

entirely. The separation of manure and crop production raises the costs 

of using manure as a fertilizer since manure must be transported off the 

originating farm for application by crop operations.

Regional specialization also matters. Signifi cant centers of large-scale 

livestock production now occur in regions—like the Southeast (poultry and 

hogs), the High Plains (fed cattle, dairy, and hogs), and the West (dairy)—

where manure production exceeds the nutrient needs of nearby crops. 

Similarly, major grain production regions in the Corn Belt have seen a longterm reorientation away from livestock and toward feed grains (Hart, 2003). 

The greater geographical separation between livestock and crop producers, 

the higher the costs of transporting excess manure. 

With the exception of the beef cow-calf sector, livestock production has been 

shifting to larger operations, as economies of scale in production provide 

larger operations with lower costs and better fi nancial returns (MacDonald 

and McBride, 2009). But large-scale operations consolidate manure as well 

as animals in a confi ned space and can produce more than is needed to meet 

agronomic needs of nearby crops. 

To illustrate the issues involved, we next use examples from milk production, 

hog fi nishing, broiler growing, and beef cattle feeding. We draw on ARMS 

Phase III for data on farm structure, while data on manure production and 

characteristics are drawn from standards published by the American Society 

of Agricultural and Biological Engineers (ASAE, 2005) 3

Dairy

A lactating dairy cow produces about 150 pounds of manure a day, while a dry 

cow produces 83 pounds—about 25 tons of manure annually, including 330 

pounds of nitrogen, 56 pounds of phosphorus, and 36 pounds of potassium.4

Farmers feed corn silage and grain to cows, and corn uses lots of nitrogen, so 

dairy farmers can take advantage of a natural cycle. If nitrogen were applied 

to corn at a rate of 125 pounds per acre, the farm would need 2.64 acres of 

corn to absorb each cow’s as-excreted manure.5 Dairy farmers also grow 

alfalfa and other forage crops and fertilize them with manure, but most of 

those crops take up fewer nutrients than corn and, hence, have greater land 

requirements to absorb each cow’s as-excreted manure. 

These acreage estimates are maximums, assuming no volatilization of 

manure occurs. As wet manure dries, some nutrients volatilize—nitrogen, 

for example, becomes airborne ammonia. Because volatilization reduces the 

amounts of nutrients remaining in stored manure, it also reduces the amount 

of crop-acres needed for spreading manure at agronomic rates, although it 

can then contribute to air pollution. The degree of volatilization varies widely 

with manure storage practices and local climate conditions. 

Dairy production has expanded rapidly in the West, and California, 

Idaho, and New Mexico are now major producers, with signifi cant areas 

 3We rely on the current standards, as 

revised in 2005. The revised standards 

are based on models of animal performance and dietary feed and nutrient 

intake.

4These are “as-excreted” estimates, 

which include both solids and liquids, 

with moisture estimated at 87 percent 

of the total, by weight (ASAE, 2005). 

Moisture percentages are 92 percent 

for fed cattle, 90 percent for fi nishing hogs, and 74 percent for broilers. 

These are averages, for specifi ed typical 

production practices, and assuming that 

a cow is dried off for 60 days a year. 

Actual manure and nutrient production 

can vary with feed characteristics, the 

feeding regimen, breeding, and animal 

performance.

5Calves and heifers also generate 

manure, albeit at a much lower rate, 

so farms that keep them onsite would 

need more land. Farms with at least 

1,000 cows in the herd accounted for 

46 percent of milk production in 2008 

(USDA/NASS, 2009).
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of production also occurring in Washington, Arizona, Kansas, and Texas. 

Some large western dairies have no crop production, and about 16 percent 

of all U.S. dairy production now occurs on farms with no crop acreage. 

These operations may have to transport manure signifi cant distances for crop 

applications.

Hogs

Today, most hogs are owned by integrators who provide contract growers 

with feeder pigs and feed and pay them to grow the pigs to market weight. 

While the integrator provides prepared feed for the hogs, growers in the 

Midwest usually also have a crop enterprise (corn, soybeans, and wheat are 

most common), and hog production yields low-cost manure nutrients as well 

as the fees paid by integrators. 

A hog in a fi nishing operation will produce 10 pounds of nitrogen, 1.7 pounds 

of phosphorus, and 4.4 pounds of potassium in the 1,200 pounds of manure 

that it excretes annually on the farm, so an operation that fi nishes 6,000 hogs 

a year could need as much as 480 acres of corn, if no volatilization occurred 

and if it were to apply nitrogen to corn at 125 pounds per acre.6 Soybeans and 

wheat take up fewer nutrients and so require more land.

The western Corn Belt, an area of intense crop production, is still a major 

center of hog production. But important production complexes are also 

located in North Carolina, Oklahoma, and Utah. Many growers in those 

States specialize in hog production—nationwide, 22 percent of market hog 

production occurs on farms with no crop acreage—and manure from these 

operations must be transported to crop farms.

Broilers

A broiler chicken produces 11 pounds of manure, on average, with 0.12 pound 

of nitrogen, 0.035 pound of phosphorus, and 0.068 pound of potassium, 

in the seven weeks that it is fed. A large-scale operation can produce 

600,000 broilers in a year. With 72,000 pounds of nitrogen in the 3,300 

tons of manure, a producer would need as much as 576 acres of corn at the 

application rates noted above, if no volatilization occurred. 

Many broiler operations are specialized, with no crop production, and very 

few grow that many acres of any crop.7 But broiler litter is relatively dry and 

thereby less costly to transport, and its high nutrient content gives it value. As 

a result, most litter is removed from the operation and spread on other farms. 

With most production in the South, broiler litter is used on crops like cotton 

and peanuts, and on bermuda grass, a nitrogen-thirsty grass used for grazing 

livestock, particularly beef cattle.

Fed Cattle

In a single year, a large cattle feedlot might fatten 35,000 cattle for 

slaughter. 8 Most are located in the High Plains, and they usually specialize 

in feeding— 68 percent of fed cattle production occurs on farms with no crop 

acreage. Nearby producers grow corn, alfalfa, grain sorghum, soybeans, and 

wheat, and cattle grazing is also popular on crop residues or grasses. 

6The broiler, hog, and fed cattle 

estimates are for a “fi nished animal,” 

covering the number of days that the 

animal is on the farm before being 

removed for slaughter.

 7Forty percent of U.S. broiler production, and 45 percent of total poultry 

production, occurs on farms with no 

crop acreage.

 8Our hog, broiler, and fed cattle 

herd and fl ock size estimates are taken 

from MacDonald and McBride (2009). 

We’ve chosen round numbers that are 

close to the median of the size distribution of production, where half of all 

sales/removals came from larger farms 

and half from smaller. They represent 

the size of farm from which a typical 

animal came.
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A feedlot steer produces much less manure than a dairy cow (4.9 tons per 

year versus 22), in part because the steer doesn’t usually spend a whole year 

in a feedlot. But when aggregated over the total number of animals (35,000) 

a large feedlot produces almost 172,000 tons of manure each year, with 

1.925 million pounds of nitrogen, 0.256 million pounds of phosphorus, and 

1.33 million pounds of potassium. A feedlot of that size, with that amount 

of nitrogen production, would need to fi nd over 15,000 acres of corn for 

the nitrogen produced, or a greater acreage of other crops. Volatilization 

substantially reduces the aggregate amount of crop acres needed in the arid 

climate of the High Plains, but substantial quantities of manure solids must 

still be moved to cropland, where they are often tilled into the soil to provide 

more soil organic matter.
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Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Use of Manure as a Crop Fertilizer

In this section, we assess the extent to which animal manure is used as 

fertilizer, as well as the conditions under which it is used. We fi rst estimate 

aggregate use—the total acres of planted cropland in the U.S., and the share 

receiving manure, by crop. We then provide greater detail, drawn from 

ARMS, for the eight major fi eld crops that account for over 70 percent of the 

acreage receiving manure. We also explore manure disposal among producers 

of manure—specifi cally, hog, dairy, and poultry operations.9

Manure Use in the Aggregate

Manure was spread as fertilizer on about 15.8 million acres of U.S. cropland 

in 2006, just 5 percent of total planted acreage of 315.8 million acres (Table 

1).10 In principle, manure could be spread on far more cropland, mitigating 

the risks that arise from excessive concentrations of manure and replacing 

high-priced commercial fertilizers. But there are several barriers to wider use. 

Over half (52 percent) of harvested crop acres were on farms with no 

livestock production at all.11 Across crops, the share of harvested acreage on 

farms with no livestock varied from 80 percent for cotton and 70 percent for 

peanuts, to 51-62 percent for soybeans, corn, wheat, sorghum, and barley, to 

9We use 2006 NASS survey data for 

estimates of planted acreage, in total 

and by commodity. All other data in 

this section are drawn from ARMS 

data.

10See box “Estimating the Amount of 

Cropland Receiving Manure” (p. 9), for 

details.

11Using 2006 ARMS Phase III data, 

which reports harvested acres. 

Table 1

Manure applications by crop, 2006

Commodity receiving 

manure PII year

Manure 

share 

(%)

2006 Acres (000) Share 

of all 

manured 

acres

Planted Manured

Major Crops

 Barley 2003 2.9 3,452 100 0.6

 Corn 2005 11.6 78,327 9,086 57.6

 Cotton 2003 2.6 15,274 397 2.5

 Oats 2005 9.0 4,168 375 2.4

 Peanuts 2004 4.2 1,243 52 0.3

 Sorghum 2003 0.7 6,522 46 0.3

 Soybeans 2006 1.3 75,562 982 6.2

 Wheat 2004 0.7 57,344 401 2.5

Subtotal 4.7 241,892 11,439

Hay and Grasses

 Hog, dairy, broiler 3,360

 Beef 791

Subtotal 6.9 60,087 4,151 26.3

All other crops 1.4 13,856 194 1.2

Total 5.0 315,835 15,784 100.0

Sources: Planted acreage estimates are drawn from USDA/NASS Acreage report released 

in June, 2006, while manured acreage estimates for major crops are based on data drawn 

from ARMS Phase II surveys, 2003 through 2006. Further explanation of the estimation 

procedures, and detail on estimation of hay and grass acreage, can be found in Text Box: 

Estimating the Amount of Cropland Receiving Manure.
8

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

less than 30 percent for oats and hay. Farms that combine crop and livestock 

production are much more likely to spread manure on their cropland.

The high cost of transporting manure limits its use on farms without 

livestock, and also limits its application to the distant fi elds operated by farms 

with livestock. Finally, the variation in nutrient loadings in manure may limit 

applications to some crops.

Among commodities, corn (9.1 million acres) accounts for over half of all 

acreage spread with manure. Corn is the country’s largest single crop, with 

24.8 percent of all planted acres in 2006. But corn’s share of manured acreage 

is more than twice as large as its share of all planted acreage, largely because 

corn is demanding of nitrogen and is grown for feed on many dairy and hog 

operations. The other major manure recipients are hay and grasses, which 

account for 4.2 million acres, and soybeans, with 0.98 million acres.12 Six 

other fi eld crops (barley, cotton, oats, peanuts, sorghum, and wheat) together 

account for a total of 1.4 million acres.13

Manure is a more important nutrient source for some crops than for others. 

Nearly 12 percent of the acreage planted to corn received manure, as did 

9 percent of oats and 7 percent of hay (Table 1). But other crops are much 

less intensive users—just over 4 percent of peanut acreage received manure, 

compared to 2.6 percent of cotton, 1.3 percent of soybeans, and less than 1 

percent of sorghum and wheat.

While corn accounts for 79 percent of manured acreage among the eight 

major fi eld crops, it accounts for 87 percent of the manure nitrogen applied 

(Figure 2). Nutrient application rates are higher for corn, wheat, and cotton 

than for other crops, with corn receiving 140 pounds of manure nitrogen 

per acre, on average, as well as 69 pounds of potassium and 91 pounds of 

phosphorus (Figure 1).14

The share of acreage receiving manure has likely risen since 2006, and 

it may continue to rise. Changes in crop prices led to a sharp increase of 

planted corn acreage after 2006. In addition, commercial fertilizer prices rose 

sharply in 2006-08, which should have led to some substitution of manure 

 12Soybeans account for 24 percent of 

harvested acres but less than 7 percent 

of acres receiving manure, likely due to 

the crop’s low nitrogen requirements.

13Manure that is applied to corn in 

one year may provide nutrients for another crop—such as soybeans—planted 

on the land in a following year. Our 

data are based only on the crop planted 

in the year the manure was applied.

14Application rates vary considerably 

across farms, due to differences in crop 

rotation, commercial fertilizer use, and 

soil characteristics. The differences in 

mean values reported in Figure 1 are 

not statistically signifi cant.

Figure 1

Manure nutrient application rates, by crop

Lbs/acre

Source: ARMS Phase II, 2003-2006.

Soybeans Corn Oats Wheat Peanuts Barley Cotton Sorghum

0

20

40

60

80

100

120

140

Nitrogen Phosphorus Potassium
9

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

In Table 1, we estimate the total number of cropland acres 

receiving manure in 2006. Since no one source provides 

an estimate of the total number of acres receiving manure 

in the U.S. in any given year, we relied on several different 

sources.

ARMS Phase II data provide estimates of planted acreage, 

and acreage receiving manure, for barley, corn, cotton, 

oats, peanuts, sorghum, soybeans, and wheat. Phase II 

data have two major weaknesses. First, the eight major 

fi eld crops are surveyed in different years. We need to 

make some adjustments to estimate manured acreage for 

each crop in 2006. Second, the eight crops accounted for 

77 percent of total planted acreage in 2006, and we must 

estimate manured acreage for the remaining cropland.

For the major fi eld crops, we assume that each crop’s 

ratio of manured to planted acreage remained constant 

over time. For example, 11.6 percent of corn acreage in 

the 2005 ARMS Phase II survey received manure, so we 

assume that 11.6 percent of 2006 acreage received manure. 

Similarly, 2.6 percent of cotton acreage in the 2003 survey 

received manure, so we assume that 2.6 percent of 2006 

acreage received manure. Estimated 2006 manured 

acreage is the product of USDA/NASS estimates of 2006 

planted acreage and each crop’s manured acreage share 

(USDA, NASS, 2006).

The eight crops listed in the top panel of Table 1 accounted 

for 77 percent of total planted acreage in 2006. The major 

omitted crop is hay, with 60.1 million planted acres, 

according to NASS. Other omitted crops accounted for 

94 percent of the remaining 13.9 million acres: Rice (2.9), 

sunfl owers (1.9), edible beans (1.5), rye (1.4), sugarbeets 

(1.4), canola (1.0), sugarcane (0.9), fl axseed (0.7) millet 

(0.6), and tobacco (0.3).

We have no ARMS Phase II surveys of hay and grasses, 

but ARMS Phase III surveys covered hog, dairy, and 

broiler producers in 2004, 2005, and 2006, respectively. 

Each questionnaire contained questions on the application 

of manure from those operations to hay and grasses. 

Respondents to the dairy survey were asked directly for the 

amount of hay acreage spread with manure—1.93 million 

acres. Broiler and hog producers were asked to list the 

major crop receiving manure, the amount of major crop 

acreage that received manure, and the total acreage that 

received manure. For broiler growers, those who listed hay 

and grasses as the primary crop, spread manure on 685,000 

acres of hay and grasses. But those who listed another 

primary crop spread manure on 63,000 acres in addition 

to the primary crop. If all of those acres were hay and 

grassland, then total hay and grassland acreage receiving 

manure could have been as high as 748,000 acres. 

Following the same rationale, we estimate that hog 

producers spread manure on 244,000-516,000 acres of 

hay and grassland. Those who listed hay and grasses as 

the primary crop spread manure on 244,000 acres. Those 

who listed another primary crop spread manure on 2.21 

million acres of the primary crop (90 percent was corn) 

and 272,000 acres of secondary crops. If all of those 

secondary acres were hay and grasses, then manured hay 

and grass acreage could have been as high as 516,000 

acres.

Taken together, hog, broiler, and dairy producers spread 

manure on between 2.86 and 3.20 million acres of hay 

and grassland. However, the ARMS commodity versions 

cover only producers in States amounting to 90 percent of 

production. Assuming that producers in other States act like 

producers in major States, we should increase our estimates 

by 11 percent, to a range of 3.17-3.55 million acres. We 

report the midpoint, 3.36 million acres, in Table 1.

Beef manure, primarily from feedlots, can also be spread on 

hay and grasses, but we have no ARMS surveys of feedlot 

manure management practices. We can, however, use the 

Phase II surveys to estimate the number of acres of the 

eight major fi eld crops that received manure from animals 

of different types—beef cattle, dairy cattle, horses, hogs, 

sheep, and poultry. We estimate that the amount of hay 

and grass acreage receiving dairy, hog, or poultry manure 

was 24.8 percent of the major crop acreage receiving that 

manure. If we assume that beef manure was spread in the 

same proportion, then we can estimate that 791,000 acres of 

hay and grasses received beef cattle manure in 2006 (Table 

1). Adding the beef estimate to the stronger estimates for 

dairy, hogs, and broilers, we can raise our estimate of hay/

grass acreage receiving manure to 4.15 million acres from 

3.36 million acres.

Finally, we need to estimate the number of acres of other 

fi eld crops receiving manure. Other fi eld crops accounted 

for 13.9 million planted acres in total. We assumed that 

acreage planted to those crops received manure in the same 

proportions as the major fi eld crops, with corn excluded. 

Under that assumption, 1.4 percent of the acreage planted 

to those crops, or 194,000 acres, received manure in 2006. 

We exclude corn because it is grown in close proximity 

to livestock operations and because of its high nitrogen 

requirements; including corn in the calculation would 

raise the estimate to 765,000 acres. In total, we estimate 

that 15.784 million acres received manure in 2006.

Estimating the Amount of Cropland Receiving Manure
10

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

for commercial fertilizers. Corn uses more nutrients and relies on animal 

manure to a greater extent than other crops. Finally, large livestock producers 

are coming under increasing regulatory pressure to remove manure that is in 

excess of agronomic needs from their operations, and removal is usually to 

other cropland off the operation. 

Which Farmers Use Manure?

Geography, commodity choices, and agronomic requirements create strong 

links between various crops and specifi c livestock species (Table 2). For 

example, dairy manure is used by more than half of the corn, oats, and barley 

operations who use manure (Figure 3). Beef manure was used by more than 

half of the sorghum and wheat operations that used manure, while poultry 

litter was used by more than half of the peanut and cotton operations that 

used manure. Only soybeans received manure from a wide variety of species. 

The linkages tend to follow from the proximity of specifi c crops to areas of 

livestock production.

Figure 2

Total tons of manure nutrients applied, by crop

1,000 tons

Source: ARMS Phase II, 2003-2006.

Nitrogen Phosphorus Potassium

Soybeans Corn Oats Wheat Peanuts Barley Cotton Sorghum

0

50

100

150

200

250

300

350

400

450

500

Table 2

Acreage receiving manure, by crop and species, 2006

Crop Acres applied (000), by source of manure

Dairy cows Beef cattle Swine Poultry Other All

Barley 54 36 4 4 2 100

Corn 5,612 1,617 1,161 472 224 9,086

Cotton 67 101 0 228 1 397

Oats 218 139 8 3 7 375

Peanuts 0 8 0 44 0 52

Sorghum 1 37 7 1 0 46

Soybeans 354 327 139 132 30 982

Wheat 107 250 26 12 6 401

All 6,413 2,515 1,345 896 270 11,439

Note: other sources include equine, sheep, and biosolids.

Source: ARMS Phase II surveys for the specifi c crops, 2003 through 2006, adjusted to a 

2006 planted acreage base using the June 2006 USDA/NASS Acreage report.
11

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Most crop enterprises cover a wide range of planted acreages, from 10 acres 

up to several thousand planted to a single crop. Smaller enterprises are more 

likely to use manure in most crop categories (Figure 4). We sorted producers 

of each of the eight fi eld crops into four size classes, depending on their 

planted acreage of the commodity, and calculated the proportion of producers 

in each size class who use manure.15 Among corn farms, 43 percent of 

operations in the smallest quartile used manure, compared to only 14 percent 

in the largest quartile. The pattern—of a higher incidence of manure use 

among smaller crop enterprises—holds for most other crops as well. Only in 

peanuts is there no clear relation between planted acreage and manure use.

The pattern likely refl ects the overall mix of commodities produced by the 

farm—that is, large fi eld crop operations are more likely to specialize in fi eld 

crop production, with no livestock enterprises, and as a result fi nd manure 

fertilizer to be more costly for them, when transport costs are considered. 

In ARMS Phase III data, which provides information on all commodities 

produced by the farm, farms with no livestock tend to have higher planted 

crop acreages than farms with livestock. For example, the mean 2006 corn 

15Specifi cally, the classes are 

quartiles, with Q1 representing the 

smallest 25 percent of crop acreages, 

Q4 representing the largest 25 percent, 

and Q2 and Q3 capturing the 26th-50th 

and 51st-75th percentiles, respectively..

Figure 3

Animal source of manure, by crop

Percent of manure applied

Source: ARMS Phase II, 2003-2006.

Beef cattle Dairy cattle Hogs Poultry Other

Soybeans Corn Oats Wheat Peanuts Barley Cotton Sorghum

0

20

40

60

80

100

Figure 4

Farmers who applied manure, by crop and size

Percent of farmers

Source: ARMS Phase II, 2003-2006.

Q1 (smallest quartile) Q2 Q3 Q4 (largest quartile)

Soybeans Corn Oats Wheat Peanuts Barley Cotton Sorghum

0

20

40

60

80

100
12

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

acreage among farms with corn but no livestock was 272 acres, substantially 

higher than the 203 acres planted by farms with corn and livestock.

Regulations can impact manure use as well. Regulations infl uenced manure 

application rates on 29 percent of the corn acres receiving manure, along 

with 26 percent of the soybean acres, 19 percent of sorghum acres, and 

7-11 percent of the other crops (Figure 5).18 Regulations may be based on 

the crop’s nitrogen or phosphorus requirements. Among producers whose 

application rates were infl uenced by regulations, nitrogen requirements 

were cited as a limiting factor by 80 percent of corn producers, 70 percent 

of soybean producers, and 90 percent of cotton producers. Phosphorus 

requirements played a major role for corn, oats, soybean, and sorghum 

producers. However, regulations infl uenced manure use much more on 

planted corn and soybean acres than for other crops (Figure 6).

 18About 7 percent of the corn farms 

that are affected by restrictions, and 

27 percent of the soybean operations, 

produce no livestock. Farms that produce only crops, and that use manure 

obtained from livestock operations, are 

not required to obtain permits for the 

discharge of manure nutrients under the 

Federal Clean Water Act. These farms 

are likely infl uenced by State and local 

restrictions.

Figure 5

Manure applications influenced by national, State, or local regulations

Percent of manured acres

Source: ARMS Phase II, 2003-2006.

Was the application rate influenced by regulations?

Was the rate restriction influenced by the crop's phosphorus requirement?

Was the rate restriction influenced by the crop's nitrogen requirement?

Soybeans Corn Oats Wheat Peanuts Barley Cotton Sorghum

0

20

40

60

80

100

Figure 6

Manure applications influenced by national, State, or local regulations

Manured acres (1,000)

Source: ARMS Phase II, 2003-2006.

Was the application rate influenced by regulations?

Was the rate restriction influenced by the crop's 

phosphorus requirement?

Was the rate restriction influenced by the crop's 

nitrogen requirement?

Soybeans Corn Oats Wheat Peanuts Barley Cotton Sorghum

0

500

1,000

1,500

2,000

2,500

3,000
13

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Manure Transport Among Farms

Most operators apply the manure produced on the farm to the farm’s cropland 

(Figure 7). Among farmers who use manure, more than 80 percent of 

barley, corn, oats, soybean, and wheat producers, and 71 percent of sorghum 

producers, apply manure produced on-farm. The exceptions occur in peanuts 

and cotton, where most manure is acquired from other farms—recall that 

peanut and cotton farms tend to rely on poultry litter, which is dry and hence 

less costly to transport and is produced on farms that often have no crop 

enterprises. 

Many farmers acquire manure for no explicit cost (they may pay to transport 

it). Some pay for the manure, and, in some places, livestock producers pay 

farmers to accept manure. Peanut and cotton operations purchase most of the 

manure that they acquire off-farm, as do most sorghum producers, but corn 

and soybean producers, who, because of their size, still account for most of 

the manure that is acquired, are more likely to obtain manure for no cost than 

to pay for it (Figure 7).

We used ARMS Phase III dairy, hog, and broiler surveys to look at manure 

removal from livestock operations (Table 3). Only 5 percent of dairy farms 

remove any manure from the farm, but 19 percent of all manure is removed. 

This is because larger farms are far more likely to remove manure, and farms 

in the largest class (2,000 animal units, about 1,500 cows) remove nearly half 

of their manure.

A similar pattern holds among hog operations. Only 16 percent of farms 

remove manure, but 26 percent of all manure is removed, and the share that 

is removed increases in larger operations. The largest operations (at least 

1,000 animal units, or 6,000-7,000 market hogs removed in a year) remove 

one-third of all the manure generated on the farm.

Broiler operations are different, because many have no cropland and because 

broiler litter is less costly to transport. Sixty-one percent of broiler litter is 

Figure 7

Manure acquisition method, by crop

Percent of manure applied

Source: ARMS Phase II, 2003-2006.

Produced their own Purchased Obtained at no cost Obtained in exchange

Soybeans Corn Oats Wheat Peanuts Barley Cotton Sorghum

0

20

40

60

80

100
14

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

removed from the operation. Even the smallest classes remove most, but the 

largest remove close to 70 percent.

Manure markets tend to be highly localized. In some areas, manure carries 

enough value as fertilizer that crop producers are willing to pay to receive it; 

in other areas, livestock producers must pay other farmers to take the manure. 

About 20 percent of the dairy and hog manure that is removed from farms 

is sold, as is 36 percent of broiler litter.17 About 60 percent of the hog and 

broiler manure that is removed from farms is given away for no exchange of 

money. Prices for manure are determined by the quantities produced in an 

area relative to the amount of nearby cropland, the mix of crops grown, and 

the cost of transporting manure. With production shifting to large livestock 

operations, which are coming under increasing pressure to reduce nutrient 

applications to their own land, we can expect to see increased manure 

removals. 

17See table 4, where about 20 percent 

of removed dairy and hog manure is 

sold, and about 36 percent of removed 

broiler litter is sold.

Table 3

Manure removal on dairy, hog, and broiler operations, by size of farm

Commodity and size class Percent with no cropland Manure removed 

(percent)

Dairy

 Farms 5 5

 Weighted by production 12 19

 By size class (AU)

 <300 3 3

 300-649 12 12

 650-999 12 23

 1,000-1,999 22 37

 2,000 or more 26 49

Hogs (market)

 Farms 10 16

 Weighted by production 19 26

By size class (AU)

 <300 7 13

 300-649 10 20

 650-999 14 29

 1,000 or more 27 33

Broilers

 Farms 32 58

 Weighted by production 29 61

By size class (AU)

 <300 33 56

 300-649 30 63

 650-999 28 63

 1,000 or more 9 68

Notes: One animal unit equals 1,000 pounds (liveweight) of livestock or poultry in inventory. 

Average liveweight of animals in inventory was assumed to be 1,350 pounds for cows and 

bulls; 375 pounds for breeding swine; for slaughter swine, one-half of the difference between 

market weight and weight when entering the farm’s inventory; and half of the average weight 

at removal for broilers.

Source: ARMS Phase III data, reported in MacDonald and McBride (2009)
15

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Substitution Between Manure and 

Commercial Nitrogen Applications

Very few farms rely exclusively on manure as a source of fertilizer because 

manure may not have the right combination of nutrients for the crop and 

because some fi elds may be at a considerable distance from manure storage 

facilities. Increased use of manure may allow farmers to reduce, rather than 

eliminate, their commercial fertilizer applications.

Three ARMS Phase II surveys (corn, oats, and soybeans) asked farmers 

whether their use of manure allowed them to reduce commercial nitrogen 

applications. The three crops accounted for 91 percent of manured acreage 

among the eight major fi eld crops, and they each have different agronomic 

requirements for nutrients; corn has among the highest nitrogen requirements 

while soybeans have among the lowest.

Manure clearly substitutes for commercial fertilizers in corn production—61 

percent of corn farmers reported that they reduced commercial nitrogen 

applications on their fi elds that received manure, and those operators cut 

their commercial nitrogen applications by 58 percent, on average (Figure 

8). Farmers who applied commercial and manure fertilizers in 2005 had 

Figure 8

Substitution between manure and commercial nitrogen

Percent, farmers or nitrogen

Source: ARMS Phase II, 2003-2006.

Farmers who reduced commercial nitrogen

Commercial nitrogen reduction by farmers

who used manure

Soybeans Corn Oats

0

20

40

60

80

100

Table 4

Manure removal transactions from livestock operations

Dairy Hogs Broiler

Percent of total production

Manure removed from operation 19 26 61

 Sold by operation 4 5 22

 Operation paid to haul it away 7 3 3

 Operation gave it away 8 18 36

Prices $ per cwt of production

 Revenue from manure sales 0.28 0.22 0.20

 Expenses to haul manure away 0.39 0.34 0.31

Source: Authors’ calculations, based on data from the Agricultural Resource Management 

Survey, Phase III, version 4, 2004 (hogs), 2005 (dairy), and 2006 (broilers).
16

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

commercial fertilizer costs that were $17.60 an acre (37 percent) lower than 

farmers who used only commercial fertilizers on corn.

Substitution is weaker for oats and soybeans; 35 percent of oats and 29 

percent of soybean producers who applied manure said that manure 

applications allowed them to reduce commercial nitrogen applications, 

although those farmers that did so cut their commercial nitrogen applications 

substantially—by 76 percent (oats) and 85 percent (soybeans). Those 

respondents who did not reduce commercial nitrogen applications were not 

necessarily applying manure and commercial nitrogen to their fi eld; they 

may have not intended to apply any commercial fertilizers, and so had no 

applications to reduce.

Methods of Manure Application

Farmers can apply manure in several ways. ARMS Phase II surveys specify 

four. It can be broadcast, or spread on top of the soil. It can be broadcast and 

then incorporated into the soil by tillage shortly after the initial application. It 

can be injected into the soil during application. Finally, it can be sprayed onto 

the soil through an irrigation system. Broadcasting may save on some costs, but 

it may also encourage run-off of nutrients and may lead to more odor problems.

Most farmers either broadcast their manure, or broadcast with incorporation, 

and the incidence of each method varies with the crop (Figure 9). Farmers 

are far more likely to broadcast without incorporation on corn, soybeans, 

and oats, while manure is usually broadcast with incorporation on cotton, 

sorghum, peanut, and wheat fi elds. 

Injection and irrigation systems require signifi cant new capital investments, 

and relatively few farmers in any commodity use them, although the former 

method does cover signifi cant shares of corn and soybean acreage (Figure 

10). Only about 10 percent of corn operators who apply manure report that 

they inject or knife manure into the soil, but the method covers 18 percent of 

manured corn acres. Similarly, 25 percent of corn operations that use manure 

choose to broadcast with incorporation, and those operations cover 36 percent 

of manured corn acres.
17

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Figure 10

Manure application method, by crop

Manured acres (1,000)

Source: ARMS Phase II, 2003-2006.

Soybeans Corn Oats Wheat Peanuts Barley Cotton Sorghum

0

1,000

2,000

3,000

4,000

5,000

Irrigation system

Broadcast without incorporation Injected or knifed in

Broadcast with incorporation

Figure 9

Method of manure application, by crop

Percent of acres receiving manure

Source: ARMS Phase II, 2003-2006.

Irrigation system

Broadcast without incorporation Injected or knifed in

Broadcast with incorporation

Soybeans Corn Oats Wheat Peanuts Barley Cotton Sorghum

0

20

40

60

80

100
18

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Impacts on Animal Operations of 

Restricting Manure Applications

Large livestock operations produce very large quantities of manure nutrients, 

often well in excess of nutrient requirements for the crops grown on the farm 

(Gollehon et al., 2001). Excess nutrients can create environmental risks, and 

manure management practices are coming under increased scrutiny in the 

regulatory and legal arenas. 

Certain large “concentrated animal feeding operations” (CAFOs) are 

required to have a pollution discharge permit under the Clean Water Act, and 

those operations must implement a nutrient management plan (NMP) as part 

of their National Pollution Discharge System (NPDES) permit. CAFOs not 

required to obtain a discharge permit must implement a NMP if they wish to 

claim the stormwater exemption contained in the Clean Water Act. By 2004-

2006, 62 percent of U.S. hogs, 60 percent of broilers, and 49 percent of dairy 

cows were on operations that had NMPs.18

An NMP requires that manure nutrients be applied at agronomic rates. If 

operations had been overapplying manure, then they have several options for 

complying with NMP requirements. They may adjust feeding regimens to 

reduce the amount of nutrients in a given amount of manure, thereby reducing 

manure and nutrient production per fi nished animal. They may acquire more 

land for spreading manure, either by expanding their own crop production or 

by persuading neighboring farmers to take their manure. Manure can also be 

dried and used as feedstock for energy production or separated into dry and 

liquid components. Dried manure that retains nutrients can be bagged and 

sold as garden fertilizer, or it can be shipped greater distances for fi eld crop 

application. 

How individual farms adjust to application restrictions depends on several 

factors, including the number of animals on the farm, amount of land 

available on the farm for spreading manure, availability of land off the farm, 

willingness of neighboring cropland operators to accept manure, type of 

crops grown, and the type of nutrient standard the farm must meet (nitrogen 

or phosphorus). 

ERS evaluated the costs of such requirements to the hog and dairy sectors 

in 2003 (Ribaudo et al., 2003). The study combined census of agriculture 

data on livestock inventories for each U.S. county with ASAE estimates of 

manure production by species to generate estimates of aggregate farm and 

county-level manure production.19 The fi ndings of this analysis can be used 

to draw inferences for how the rules embodied in NMPs would affect all 

animal feeding operations, not just those regulated by EPA. The results of 

this analysis are summarized here.

Hogs

Ribaudo et al. (2003) used the 1998 hog ARMS to estimate the amount of 

additional land each farm would need to meet nitrogen (N) and phosphorus 

(P) based standards, and the cost of meeting a nutrient management plan. 

They accounted for the different manure storage technologies used by 

18In 2004 (hogs), 2005 (dairy), and 

2006 (broilers). Correspondingly, 30 

percent of hog farms, 32 percent of 

dairy farms, and 60 percent of broiler 

farms had an NMP. Plans cover more 

animals than farms because larger 

farms are more likely to be required to 

have one.

19The Ribaudo et al. estimates are 

based on older 1988 ASAE standards, 

and have not been updated to refl ect the 

2005 revision of the standards.
19

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

hog operations, which affect both the nutrient content and the weight of 

the material that must be moved and applied. For example, operations in 

the Southeast tend to use lagoons, which greatly dilute manure, and apply 

waste to fi elds with irrigation sprinklers. Operations in the Midwest tend to 

use slurry tanks or pits and to apply manure with mobile equipment. The 

cost of implementing a nutrient management plan has three components: 

recordkeeping and testing, application, and transportation. All three were 

accounted for in the analysis.

In 1998, the hog sector was dominated by four types of operations—farrowto-fi nish (50 percent), feeder pig-to-fi nish (31 percent), farrow-to-feeder 

pig, and weanling-to-feeder pig operations. Most hog farms (85 percent) 

contained less than 300 animal units (defi ned as 1,000 lbs of live weight). 

Twelve percent contained between 300 and 1,000 animal units, and only 

3 percent were large, with at least 1,000 animal units. When looking at 

production, however, large operations produced 34 percent of all hogs (Table 

5). It is these operations that were the focus of EPA’s 2003 regulations.

Farm size plays a major role in whether an animal feeding operation is 

defi ned as a CAFO and regulated by EPA. EPA defi nes size for the purpose 

of Clean Water Act implementation on the basis of Animal Units (AU) 

different from USDA’s defi nition of animal units (live weight). EPA defi ned 

an animal unit as 2.5 swine weighing more than 25 kg. Those operations with 

more than 1,000 AU were classifi ed as large and generally made up the bulk 

of operations that needed a discharge permit from EPA. 

In the Ribaudo et al. analysis, operations were classifi ed into three size 

classes: large (>1,000 AU), medium (between 300 and 1,000 AU), and small 

(less than 300 AU). Operations with less than 27 animals were dropped from 

the analysis, on the assumption that these are not confi ned animal feeding 

operations. Also, the EPA size defi nitions did not account for hogs weighing 

less than 25 kg, so those operations containing only pigs smaller than 25 kg 

(wean to feeder) were dropped from the analysis. 

For each farm in the sample, the acreage needed to apply manure at 

agronomic rates was compared with the acreage reported as receiving manure 

and with the total acreage operated by the farm deemed suitable for receiving 

manure. Farms not meeting the standard were assumed to spread on a larger 

area, which may have necessitated moving manure off the farm to cropland 

and pasture operated by other farmers. Ribaudo et al. examined the impact of 

the standard for all three size classes across fi ve regions.

Table 5

Characteristics of hog producers, by size class, 1998

Item <300 units 300-1,000 units >1,000 units

Number of hog farms 52,718 7,153 2,100

Percent of farms 85 12 3

Percent of sales 30 33 37

Percent of production 33 33 34

A unit represents 1,000 lbs of live weight.

Source: 1998 hog ARMS
20

Manure Use for Fertilizer and for Energy / Report to Congress

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On average, small farms were spreading on enough land to meet a nitrogen 

standard and would not be much affected by a requirement to meet an 

agronomic rate, although this varied by region (Table 6). Medium farms 

would need, on average, to increase the amount of land receiving manure by 

33 percent. Large farms had the greatest need to spread on more land. On 

average, the amount of land needed for spreading would have had to increase 

by 114 percent. In addition, a phosphorus-based standard would greatly 

increase the amount of land required for spreading manure. Large farms 

would need, on average, about 1,000 acres of additional land for spreading. 

The cost of meeting the application limit depends heavily on whether a 

farm has enough of its own land, or whether it must transport manure off 

the farm. If moved off the farm, the willingness of nearby crop producers 

to use manure is a major factor in how far manure must be hauled. Data on 

willingness-to-accept manure (WTAM) was lacking when the study was 

conducted, so the authors looked at a range, from 20 to 80 percent. As seen 

from Figure 11, per-AU costs are negative for medium and large farms and 

in most regions when willingness to accept manure exceeds 20 percent 

(because manure then has value, and producers obtain revenue for it). The 

Table 6

Percentage of hog farms meeting N-based and P-based standards, by region and EPA size class, 1998

Region Farms with 

confi ned hogs

Farms meeting N-based 

standard

Farms meeting P-based 

standard

Farms with 

adequate land for 

N-based standard

Farms with adequate 

land for P-based 

standard

Number Percent

Eastern Corn Belt

<300 AU 5,891 44.5 16.4 85.1 66.7

300 – 1,000 AU 2,658 34.8 7.3 84.4 59.0

>1,000 AU 1,110 20.1 0 56.1 25.1

Western Corn Belt

<300 AU 10,903 50.1 11.8 92.1 72.1

300 – 1,000 AU 7,744 37.9 9.9 82.0 48.9

>1,000 AU 2,025 26.9 8.8 66.5 31.0

Mid-Atlantic

<300 AU 423 15.4 1.1 54.9 46.9

300 – 1,000 AU 582 14.1 0 23.0 10.8

>1,000 AU 1,214 4.5 0 17.3 2.4

South

<300 AU 1,236 32.5 11.2 81.7 68.6

300 – 1,000 AU 488 21.7 0.6 67.3 43.8

>1,000 AU 177 13.3 7.9 32.0 16.6

West

<300 AU 393 19.2 7.6 28.2 25.4

300 – 1,000 AU 108 0 0 0 0

>1,000 AU 174 0 0 29.4 0

Nation

<300 AU 18,846 45.8 12.8 87.1 68.7

300 – 1,000 AU 11,580 35.0 8.3 78.2 48.7

>1,000 AU 4,700 18.0 4.1 48.8 20.6

AU = 2.5 hogs of more than 25 kg.

Operations with fewer than 27 hogs, or containing only hogs weighing less than 25 kg, were dropped from the analysis.

Source: Ribaudo et al. (2003)
21

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

<300 AU

Net cost ($) per AU

Willingness to accept manure (percent)

-5

0

5

10

15

20

0 20 40 60 80 100

E. Corn Belt

W. Corn Belt

Mid-Atlantic

South

West

300-1,000 AU

Net cost ($) per AU

Willingness to accept manure (percent)

-5

0

5

10

15

20

0 20 40 60 80 100

E. Corn Belt

W. Corn Belt

Mid-Atlantic

South

West

>1,000 AU

Net cost ($) per AU

Willingness to accept manure (percent)

-5

0

5

10

15

20

0 20 40 60 80 100

E. Corn Belt

W. Corn Belt

Mid-Atlantic

South

West

Figure 11

Average net cost of applying manure from hog farms following a 

nitrogen standard, by region

Source: Ribaudo et al., 2003.
22

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Mid-Atlantic and West regions showed higher costs, primarily because of the 

relative scarcity of cropland suitable for receiving manure (manure must be 

transported farther). Among farms affected by a standard, small farms tend 

to have higher unit costs of meeting a standard. Costs are generally higher for 

P-based plans, but again, become negative for medium and large operations 

when willingness to accept exceeds 20 percent, in most regions (Figure 12).

To put these costs in context, they can be compared to production costs 

(operating costs plus allocated overhead). Data from ARMS indicated that hog 

production costs ranged from $360 to nearly $1,000 per animal unit for 1998, 

depending on the region, size of operation, and type of operation. At a high 

WTAM (80 percent), production costs would increase 1 percent or less across 

all regions and all size classes, for meeting either an N- or P-based standard. 

At lower WTAM, impacts on production costs are noticeably higher for large 

operations than for small and medium operations in some regions. Under an 

N-based standard with a WTAM of 20 percent, the impact on production 

costs for large operations in the Corn Belt are negligible and slightly higher 

Table 7

Average acreage being used for spreading and average acreage needed to meet nutrient standard 

on hog farms, by region and EPA size, 1998

Region Manure 

volume

Acres 

being 

used

Acres on 

the farm1

Acres needed

N-based 

standard

P-based standard, 

baseline phytase

P-based 

standard, all 

phytase

Eastern Corn Belt 1,000 gal Acres

<300 AU 382 66.6 365.2 53.8 193.9 140.1

300 – 1,000 AU 1,027 110.7 705.2 145.0 466.6 352.4

>1,000 AU 4,081 179.6 756.7 349.0 1,143.5 863.7

Western Corn Belt

<300 AU 514 75.9 451.4 61.6 229.2 161.9

300 – 1,000 AU 1,492 119.4 535.5 147.4 493.2 355.2

>1,000 AU 5,204 262.8 789.5 368.7 1,206.8 882.0

Mid-Atlantic

<300 AU 1,053 16.1 144.0 57.6 172.3 135.5

300 – 1,000 AU 3,800 39.2 134.5 151.7 331.1 242.7

>1,000 AU 12,141 68.7 247.3 397.9 1,166.0 851.5

South

<300 AU 998 39.5 342.3 49.8 115.3 82.2

300 – 1,000 AU 2,591 57.6 688.2 127.7 366.4 266.0

>1,000 AU 8,067 139.7 276.7 578.8 833.1 693.3

West

<300 AU 1,646 40.7 163.0 127.5 170.7 120.2

300 – 1,000 AU 3,558 59.2 5.7 138.6 272.3 218.9

>1,000 AU 17,946 139.4 258.6 736.6 1,992.6 1395.2

Nation

<300 AU 539 68.5 404.5 59.6 208.2 148.4

300 – 1,000 AU 1,562 110.2 556.9 146.2 471.5 344.0

>1,000 AU 7,302 184.2 603.5 393.6 1,196.9 882.1

1Acres owned or leased suitable for receiving manure.

Source: Ribaudo et al. (2003)
23

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Figure 12

Average net cost of spreading manure from hog farms following a

phosphorus standard, baseline phytase use, by region 

-5

0

5

10

15

20

<300 AU

Net cost ($) per AU

Willingness to accept manure (percent)

0 20 40 60 80 100

E. Corn Belt

W. Corn Belt

Mid-Atlantic

South

West

-5

0

5

10

15

20

25

300-1,000 AU

Net cost ($) per AU

Willingness to accept manure (percent)

0 20 40 60 80 100

E. Corn Belt

W. Corn Belt

Mid-Atlantic

South

West

-5

0

5

10

15

20

25

30

>1,000 AU

Net cost ($) per AU

Willingness to accept manure (percent)

0 20 40 60 80 100

E. Corn Belt

W. Corn Belt

Mid-Atlantic

South

West

Source: Ribaudo et al., 2003.
24

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

for medium and small operations (Figure 13). In the other regions, production 

costs increase from 1 to 2 percent for large operations. For a P-based 

standard, the increases in costs for regions other than the Corn Belt are larger, 

ranging from 2 to 3.5 percent for large operations. 

Animal diet modifi cation is one approach for reducing nitrogen and 

phosphorus content of excreted manure. The phosphorus content of hog 

manure can be reduced by using reformulated feed containing the enzyme 

phytase. Phytase enables hogs to better utilize phosphorus in grain, thus 

reducing the need to add dicalcium phosphate or other inorganic phosphorus 

additives common in hog feed mixes. The addition of phytase to feed can 

reduce the P content of manure by up to 45 percent and, because phytase 

replaces dicalcium phosphate in hog diets, usage may also reduce feed costs. 

This reduction is seen in the study results. The amount of land needed by 

farms having to spread manure is reduced by about 27 percent for all size 

classes. Large operations would benefi t most if phytase were used in feed, 

as hauling costs make up a larger share of the costs of meeting a P-based 

standard (Figure 14). 

The hog sector changed measurably in the decade after 1998. We looked 

at how those changes might alter the Ribaudo et al. fi ndings, by comparing 

data from 1998 with data from the 2004 ARMS hog version. The number of 

small farms fell greatly, while the number of medium and large operations 

increased—large hog operations with at least 1,000 AUs accounted for 46 

percent of production in 2004, up from 34 percent in 1998. 

Perhaps in response to public pressure to reduce environmental impacts, 

larger operations more often removed manure from the farm, added microbial 

phytase to hog feed, and followed a comprehensive nutrient management plan 

(Key, McBride, and Ribaudo, 2009). Whereas 23 percent of hog manure was 

removed from farms in 1998, farms removed 31 percent of all hog manure in 

2004. With more manure removed, and with manure application intensities 

(animal units per acre) on large farms dropping by 15 percent, overall 

application intensities did not change between 1998 and 2004, even though 

production shifted to larger farms. Farmers also took steps to alter the nutrients 

in manure; in 1998, 4 percent of hog producers, accounting for 12 percent of 

production, added phytase to their feed. By 2004, 13 percent of producers, 

accounting for 30 percent of production, were doing so. These steps make it 

easier for large farms to meet a nutrient application standard, thus reducing 

the added cost of meeting a standard. Similar changes were not observed for 

small and medium sized operations. Application intensity increased for small 

and medium sized operations, implying that the costs of meeting a nutrient 

standard may be higher among smaller operations than in 1998.

Dairy

Ribaudo et al. (2003) also analyzed the impacts a nutrient application 

standard would have on dairies, using data from the 2000 dairy ARMS 

survey. As with hogs, the dairy sector has many small operations. In 2000, 

92 percent of all dairies had fewer than 200 head. Less than 1 percent of 

operations had 1,000 or more cows, but they contained over 19 percent of the 

sector’s cow inventory and accounted for 23 percent of production. 
25

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Figure 13

Increase in production costs for hog farms under a nutrient standard

with a willingness-to-accept-manure of 20 percent, by size

<300 300 >1,000

-1.0

-0.5

0

0.5

1.0

1.5

2.0

2.5

N-based standard

Percent change in production costs

Operation size (AU)

E. Corn Belt

W. Corn Belt

Mid-Atlantic

South

West

<300 300-1,000 >1,000

-1.0

-0.5

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

P-based standard

Percent change in production costs

Operation size (AU)

E. Corn Belt

W. Corn Belt

Mid-Atlantic

South

West

Source: Ribaudo et al., 2003.
26

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Figure 14

Net cost of spreading manure from hog farms following a

phosphorus standard with all farms using phytase, by region

-5

0

5

10

15

20

<300 AU

Net cost ($) per AU

Willingness to accept manure (percent)

0 20 40 60 80 100

E. Corn Belt

W. Corn Belt

Mid-Atlantic

South

West

-5

0

5

10

15

20

300-1,000 AU

Net cost ($) per AU

Willingness to accept manure (percent)

0 20 40 60 80 100

E. Corn Belt

W. Corn Belt

Mid-Atlantic

South

West

-5

0

5

10

15

20

25

>1,000 AU

Net cost ($) per AU

Willingness to accept manure (percent)

0 20 40 60 80 100

E. Corn Belt

W. Corn Belt

Mid-Atlantic

South

West

Source: Ribaudo et al., 2003.
27

Manure Use for Fertilizer and for Energy / Report to Congress

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Operations with fewer than 25 animals were eliminated from the analysis 

on the grounds that they were not confi nement operations. Dairy farms were 

grouped into three size classes based on the EPA defi nition of animal unit, 0.7 

mature dairy cows (Table 8). Two regions were considered, North and South. 

Most small dairies would not have been affected by a nitrogen-based 

standard, as they were not overapplying manure N, although there are 

regional differences (Table 8). Most medium and large dairies generally 

do not own enough land for applying all their manure under an N-based 

standard, and must move some off the farm. As with hog farms, large 

operations would have to increase the amount of land receiving manure 

the most (Ribaudo et al., 2003) (Table 9). If farms were required to meet a 

phosphorus-based standard, the amount of land needed off the farm would 

increase substantially, as well as the number of farms needing to move 

manure off the farm. 

The net costs of meeting a nitrogen based applications standard would be 

highest for medium-sized dairies (Figure 15). Even with a high willingness to 

accept manure, manure application costs are about $10 per AU for mediumsized dairies. For large operations, costs approach 0 as WTAM approaches 80 

percent. Small operations also see costs that are higher than large operations. 

Meeting a P-based standard would increase the net costs of spreading manure 

for all size classes because of the larger amount of land needed for spreading 

(Figure 16). Costs approach $20 per AU for medium operations, even at high 

WTAM. Costs are much higher at lower WTAM. 

Table 8 

Percentage of dairy farms meeting N-based and P-based standards, by region and EPA size class, 2000

Region

Farms with 

confi ned dairy 

cows

Farms meeting N-based 

standard

Farms meeting P-based 

standard

Farms with 

adequate land for 

N-based standard

Farms with adequate 

land for P-based 

standard

Number Percent

South

<300 AU 1,998 19.5 4.8 33.2 18.4

300 – 1,000 AU 1,921 5.7 0 8.5 1.1

>1,000 AU 1,268 21.3 1.0 26.6 2.6

North

<300 AU 55,622 72.1 27.3 91.2 66.4

300 – 1,000 AU 1,893 46.4 10.9 66.2 31.6

>1,000 AU 603 26.5 0 26.5 0

Nation

<300 AU 57,620 70.8 26.7 89.8 65.3

300 – 1,000 AU 3,814 27.5 5.8 39.4 17.5

>1,000 AU 1,871 23.0 0.7 26.6 1.8

AU = 0.7 mature dairy cow.

Operations with fewer than 25 cows were dropped from the analysis

Source: Ribaudo et al. (2003)
28

Manure Use for Fertilizer and for Energy / Report to Congress

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When viewed in relation to production costs (operating costs plus allocated 

overhead), the increase in costs from meeting a nutrient standard are 

relatively small, even when willingness to accept manure is low (Figure 

17). As a percentage of production costs, impacts of a manure application 

standard would be about 1 percent or less for all regions and size classes, 

assuming a high willingness to accept manure (80 percent). Small operations 

saw the smallest impacts on production costs, primarily because of the 

adequacy of their land base. Even for a lower willingness to accept (20 

percent), productions costs for any size class would increase less than 2 

percent for an N-based standard, and less than 3.5 percent for a P-based 

standard. 

Since 2000, dairy industry production has shifted to much larger farms. 

Farms with fewer than 100 cows accounted for 20 percent of all milk cows 

in 2008, down from 34 percent in 2000, while farms with at least 1,000 

accounted for 42 percent of all cows in 2008, compared to 19 percent in 

2000. An ARMS dairy version was again conducted in 2005, allowing for 

comparisons to the 2000 data used in Ribaudo et al. (2003).

The structural shifts, along with expanding regulation, have placed more 

production under nutrient management plans (49 percent of cows were 

covered by NMPs in 2005, compared to 40 percent in 2000). There was 

some increase in manure removal from farms, from 16 to 19 percent of all 

manure, between 2000 and 2005. Dairies could also take steps to alter feed 

formulations so as to reduce manure nutrients—operations covering 11 

percent of all cows were adding phytase to diets in 2005.

In general, large hog and dairy operations consolidate substantial amounts of 

manure, and continued structural change is leading to greater consolidation. 

Large operations will need to comply with regulations by expanding the 

amount of cropland that manure is applied to, either by operating more 

Table 9 

Estimated acreage being used for spreading and acreage needed to 

meet nutrient standard on dairy farms, by region and size, 2000

Region

Acres 

being 

used

Own available acres1

Acres needed

N-based 

standard

P-based 

standard

South Acres

<300 AU 52.6 76.5 143.4 262.0

300 – 1,000 AU 129.4 114.8 343.8 795.3

>1,000 AU 310.4 319.6 661.3 2001.0

North

<300 AU 100.7 207.0 63.6 147.2

300 – 1,000 AU 328.3 584.0 338.8 756.8

>1,000 AU 330.9 391.4 564.2 1,979.0

Nation

<300 AU 99.5 203.8 65.6 150.1

300 – 1,000 AU 235.9 366.0 341.1 774.6

>1,000 AU 316.9 342.4 630.5 1,994.0

1Acres owned or leased suitable for receiving manure.

Source: Ribaudo et al. (2003)
29

Manure Use for Fertilizer and for Energy / Report to Congress

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Figure 15

Average cost of applying manure from dairy farms following a

nitrogen-based standard, by region

<300 AU

Net cost ($) per AU

Willingness to accept manure (percent)

0 20 40 60 80 100

South

North

0

5

10

15

20

25

30

35

40

300-1,000 AU

Net cost ($) per AU

Willingness to accept manure (percent)

0 20 40 60 80 100

South

North

0

10

20

30

40

50

60

>1,000 AU

Net cost ($) per AU

Willingness to accept manure (percent)

0 20 40 60 80 100

South

North

0

10

20

30

40

50

Source: Ribaudo et al., 2003.
30

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Figure 16

Net cost of spreading manure following a phosphorus-based standard, 

by region

<300 AU

Net cost ($) per AU

Willingness to accept manure (percent)

0 20 40 60 80 100

South

North

0

10

20

30

40

50

60

300-1,000 AU

Net cost ($) per AU

Willingness to accept manure (percent)

0 20 40 60 80 100

South

North

0

20

40

60

80

100

>1,000 AU

Net cost ($) per AU

Willingness to accept manure (percent)

0 20 40 60 80 100

South

North

0

20

40

60

80

100

Source: Ribaudo et al., 2003.
31

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

manured acres on the farm or by removing manure to cropland on other 

farms, or they will need to reduce nutrient loadings through changes in 

feeding. The Ribaudo et al. (2003) estimates suggest that the likely costs 

required to meet NMPs, while substantial in the aggregate, are nevertheless 

relatively small fractions of total production costs. If those fi ndings are 

accurate, they suggest that the cost advantages held by large farms will not be 

erased, or even substantially modifi ed, by the types of regulations captured 

in nutrient management plans (in some cases, they are enhanced slightly). In 

that case, such regulations are unlikely to lead to major structural changes in 

the industries.20

20There may nevertheless be signifi -

cant geographic changes in livestock 

feeding driven by differences in 

production costs, some of which may in 

turn be driven by future urban development, State and local moratoria on large 

operations, or persistent geographic 

differences in NMP compliance costs. 

Our evidence suggests that these factors 

may infl uence the location but not the 

size structure of production.

Figure 17

Increase in production costs for meeting a nutrient standard

with a willingness-to-accept-manure of 20 percent for dairy farms, 

by size

N-based standard

Percent change in production costs

Size of operation (AU)

South

North

<300 300 >1,000

0

0.5

1.0

1.5

2.0

2.5

P-based standard

Percent change in production costs

Size of operation (AU)

South

North

<300 300 >1,000

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Source: Ribaudo et al., 2003.
32

Manure Use for Fertilizer and for Energy / Report to Congress

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Competition from Energy Uses of Manure

There is growing interest in using manure as a feedstock for energy 

production, driven by rising energy prices and growing concerns over the 

environmental risks associated with excess applications of manure nutrients 

and with fossil fuel energy production. Two types of manure-based energy 

production are in current commercial use in the United States.21

Anaerobic digesters are in use on dairy and hog farms, and a few community 

digesters also serve multiple operations in a local area. Digesters capture 

biogas, which contains methane, carbon dioxide, and trace amounts of 

other gases, from manure. The gas can be used as a fuel for boilers, heaters, 

chillers, and generators, but it can also be cleaned and conditioned for 

insertion into a natural gas (97 percent methane) pipeline. Most current 

applications burn the gas for on-farm electricity generation.

Manure can also be treated and burned as a feedstock in electricity 

generating plants. Manure must be transported from farms to centralized 

generating plants to realize scale economies in combustion. Several such 

plants are in operation in England and Scotland. A plant using fed cattle 

manure fi rst operated in California in 1987; that plant is currently idled, but 

a plant relying on turkey litter recently opened in Minnesota, and others are 

under construction in Connecticut (using litter from an egg-laying operation) 

and Texas (using cattle manure).

Manure to Energy Systems 

in Current Commercial Use

In the manure storage systems that are typically used on large dairy and hog 

operations, little oxygen can dissolve into the mix, which creates anaerobic 

(without air) conditions. Certain microbes that are naturally found in manure 

feed on organic materials in the manure. The bacteria function best in 

anaerobic conditions, and they give off biogases, primarily methane and 

carbon dioxide. Methane is the primary component of natural gas and is a 

clean-burning fuel. 

If methane can be captured from manure, it can be used as a feedstock for 

electricity generation. Farmers could then reduce their purchases of electricity 

and fuels, and might be able to sell excess electricity or methane. Society 

can gain because an existing product, manure-based methane gas, would 

replace some fossil fuels used for the same purpose. In addition, the manure 

effl uent that is left after anaerobic digestion has few remaining decomposable 

compounds. Decomposition is what creates odor, so digestion also provides a 

solution to odor problems.22

Anaerobic digestion presents several important technical challenges in 

on-farm applications. An anaerobic digester is a sealed air-tight container 

that more effectively excludes oxygen from the manure and encourages a 

higher level of biogas production. Manure is added daily to the digester, and 

spends about 20 days fl owing through the digester to the effl uent storage 

and handling system. Growth of methane bacteria can be encouraged 

by maintaining higher temperatures, so heat must usually be added to a 

21In this section, we rely on media 

reports, academic journal articles, 

and EPA databases for source data on 

manure-to-energy projects, and we use 

ARMS data to generate estimates of 

the potential avoided costs of on-farm 

electricity generation.

22The gas that digesters capture is 60-

70 percent methane and 30-40 percent 

carbon dioxide, another greenhouse 

gas. Carbon dioxide could be separated, 

refi ned, and cooled for industrial uses, 

but that would require additional capital 

investment.
33

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

digester—typically via pipes running through the digester—and regulated 

for maximum gas production. The bacteria are quite pH-sensitive, so high 

alkalinity must be maintained in digesters, through added ingredients (lime) 

and by carefully regulating the fl ow of organic material to the digester. A 

variety of materials, such as salts, heavy metals, ammonia, and antibiotics, 

are toxic to methane bacteria, and must be carefully controlled.

The potential for generating methane is greatest when manure is collected 

and stored as a liquid, slurry, or semi-solid. Biogas potential is greatest at 

large dairy and swine operations because they use liquid or slurry manure 

management systems, and they have attracted the most attention. Manure 

managed in solid form, as in the fed cattle and poultry sectors, offers little 

opportunity for current digester designs.23

While there are a few centralized community digesters, most are on-farm 

systems. Manure can also be used as a feedstock for power plants, where the 

manure is incinerated and the heat from combustion creates steam for turning 

electricity-generating turbines. The manure produced on dairy and hog farms 

is costly to transport, and combustion is diffi cult to maintain with such highmoisture fuels, so combustion plants focus on poultry litter and fed cattle 

manure, which have high energy content and lower moisture content and 

transportation costs. The latter consideration is important because a power 

plant may draw in a large volume of manure from a signifi cant catchment 

area.

But the moisture content of dry manure remains higher and more variable 

than non-manure feedstocks, making it harder to sustain combustion. Manure 

can create signifi cant nitrous oxide emissions when burned, and it creates 

large volumes of ash residue. Some compounds added to feeds may present 

air pollution concerns when the litter is burned; on the other hand, manure is 

low in sulphur content compared to other fuels. These technical barriers stand 

in the way of widespread adoption of manure for energy production.

Extent of Current Adoption 

Manure-to-energy systems are in limited commercial use in the U.S. By 

the summer of 2008, 91 commercial dairy farms were using digesters and 

another 64 had projects in the construction, design, or planning (CDP) phase. 

Farms in the two categories accounted for 0.2 percent of all dairy farms 

and 2.9 percent of all dairy cows in the U.S. (Table 10). In addition, the 

Environmental Protection Agency reports that 17 hog farms had operating 

digesters by the summer of 2008, with the manure supplied by 355,000 hogs. 

But that amounts to just 0.5 percent of the inventory of hogs and pigs on U.S. 

farms (0.6 percent when the 6 farms in the CDP phase were added).

Larger dairy and hog farms are more likely to adopt digesters, but adoption 

is not widespread even among them (Table 11). About 4.5 percent of dairy 

farms with at least 2,000 cows have digesters, and another 3.4 percent are in 

the CDP phase, but they account for just 8 percent of the cows on dairy farms 

with at least 2,000 head.24

Combustion plants are still in their commercial infancy in the U.S. An 18.5- 

megawatt plant in El Centro, California, was opened in 1987 and utilized the 

23A large digester under construction in Alberta, Canada, will use cattle 

feedlot manure and a newly developed 

separation technology to remove sand 

and dirt from the manure before digestion (Kryzanowski, 2009). The biogas 

will be used to generate electricity to 

power an onsite ethanol plant, with excess electricity to be sold into the power 

grid.

24Most of the hog operations with 

digesters had at least 5,000 hogs in 

inventory, which is a relatively large 

hog feeding operation, and two large 

complexes had over 100,000.
34

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

manure produced by 100,000 cattle, just under 1 percent of all feedlot cattle. 

The plant was idled but acquired by GreenHunter Energy in 2007, which 

expects to reopen the plant by 2009. The plant has a 30-year supply contract 

with a California utility.

A large combustion plant was opened in Benson, Minnesota, in May of 

2007. The plant, called Fibrominn, sells the electricity it generates to Xcel 

Energy, a Minnesota-based public utility, under a 21-year contract. The 

plant’s 55-megawatt generating capacity helps Xcel meet a mandate set by the 

Minnesota legislature for each of the State’s utilities to realize 125 megawatts 

from biomass or wind power. 

The Benson plant utilizes turkey litter from about 300 farms within a radius 

of 100 miles. The farms currently supplying the plant account for about 40 

percent of Minnesota turkey production, or about 6.6 percent of U.S. turkey 

production, although they do not provide all of their litter to Fibrominn 

(some is used on-farm as fertilizer). Fibrominn was fi nanced by Fibrowatt, 

a company whose management developed four poultry-litter plants in the 

Table 11

Farm size and adoption of anaerobic digesters

Herd size 

of farm All U.S. dairy farms

Farms with digesters, by status

Steady state/startup Construction/

Design/Planned

Farms Cows Farms Cows Farms Cows

<500 68,295 4,656,000 18 4,973 8 1,575

500-999 1,700 1,139,000 22 16,424 16 11,450

1000-1999 920 1,212,000 24 31,107 20 27,010

>1999 595 2,106,000 27 87,001 20 82,300

All farms 71,510 9,112,000 91 139,505 64 122,325

Source: U.S. Environmental Protection Agency, Agstar Program, Anaerobic Digester 

Database.

Table 10

Anaerobic digesters on dairy farms, by region

Farms and cows, by status of digester projects

States Total milk 

cows Steady state/start-up Construction/

Design/Planned

Farms Cows Farms Cows

CA 1,780,000 15 28,162 4 10,795

Other West* 1,345,000 11 27,275 3 6,650

IN/MI/OH 759,000 4 12,400 10 44,870

NY/PA/VT 1,333,000 29 26,943 23 28,370

WI 1,243,000 19 28,000 13 15,750

IA/IL/MN 758,000 6 7,350 11 15,900

All 9,112,000 91 139,505 64 122,335

*ID/OR/TX/UT/SD/WA

Source: U.S. Environmental Protection Agency, Agstar Program, Anaerobic Digester 

Database.
35

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

United Kingdom. Fibrowatt is pursuing projects for similar plants in major 

broiler producing regions in North Carolina, Maryland, Arkansas, and 

Mississippi. Although the company has announced a site in North Carolina, 

construction has not commenced there or at the other locations.25

Another combustion plant has been proposed in Bozrah, Connecticut, by 

Clearview Renewable Energy. The 30-megawatt plant would utilize litter from 

a large egg-laying operation (340 tons a day) and waste wood from pallets and 

tree trimmings. It has received approval from the State’s utility board and a 

site on the egg farm has been selected, but construction has not begun.

Panda Ethanol has a plant under construction in Hereford, Texas, which 

would use manure from feedlots to generate the steam needed to operate 

an ethanol refi nery. The plant would gasify about 500,000 tons of manure a 

year; feedlots within 50 miles of the plant generate 2.1 million tons annually. 

Panda has announced plans to build three other plants, although the Hereford 

plant is the only one currently under construction.

Drivers of Adoption

Few manure-to-energy projects are now in commercial operation, but there 

is widespread interest in such projects and considerable potential for future 

growth. In order to understand the prospects for future growth, and the limits 

to current adoption, it is important to understand the incentives faced by 

individual decision makers.

Centralized combustion facilities require a substantial capital investment. 

Even though Fibrominn secured an agreement to sell its electricity to Xcel in 

August of 2000, it was unable to secure the $202 million in fi nancing for the 

plant from a consortium of insurance companies until late 2004. 

Moreover, Fibrominn’s costs of electricity generation exceed those at 

conventional coal-fi red plants, even though the plant’s size allows it to realize 

lower costs than smaller biomass facilities. A Minnesota legislative mandate, 

requiring Xcel to generate 125 MW of power from biomass and wind 

sources, played an important role in securing the electricity supply contract 

for Fibrominn. Public support, either indirectly through mandates or directly 

through payments, may be critical for widespread adoption of manure-toenergy systems.26

Specifi c location also plays an important role. A viable combustion plant 

needs large local supplies of excess litter to minimize its costs of purchasing 

and transporting fuel, as well as easy transmission connections to limit its 

cost of transporting electricity.

The Fibrominn plant burns about 2,000 tons of litter a day. Half is acquired 

under long-term contracts from farmers in the immediate area, and the 

rest is trucked in from farms within a 100-mile radius. The plant pays 

farmers a price, 3-5 dollars per ton of litter, that matches what they can earn 

from selling the litter for fertilizer. The plant is also located near a new 

115-kilovolt transmission line, and a co-located plant produces and sells 

phosphate fertilizer from the ash residue of the combustion process. 

 25Broilers are an attractive potential 

feedstock because broiler production 

generates about 6 times as much litter 

as turkey production, based on ASAE 

standards for per animal manure production by broilers, male turkeys and 

female turkeys, ASAE estimates of the 

fraction of males in turkey production, 

and USDA estimates of annual broiler 

and turkey slaughter.

26 The proposed Clearview plant in 

Connecticut is expected to cost $140 

million. The project was spurred by a 

legislative mandate imposed on Connecticut utilities, and fi nancing was 

secured through the offer of long-term 

supply contracts offered to renewable 

energy providers by a State agency. 
36

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

The California plant is located in California’s Imperial Valley, with 400,000 

head of feedlot cattle within a 20-mile radius. When operating, the plant 

took about one-quarter of the area’s manure. The proposed Connecticut plant 

would be located on an egg farm; with limited crop production in the area, 

the farm faces a problem of excess nutrients. The Texas ethanol plant, now 

under construction, is located in a dense region of cattle feedlots, and has 

contracted to acquire manure for no cost, save for the expense of trucking it 

to the site.

Most anaerobic digesters are on-farm systems, so the costs and benefi ts facing 

the individual farmer are crucial in adoption. 

The costs include:

• Capital costs, for digester and generation equipment;

• Operation and maintenance (O&M) expenses;

• Costs of adapting existing manure handling and storage to biogas 

systems; and

• The farmer’s time costs in learning about and maintaining the system, 

which could amount to an hour a day.

The fi nancial benefi ts include:

• Avoided costs of electricity, if the biogas is used onsite for generation that 

replaces electricity purchased from the electric utility;

• Avoided propane, fuel oil, or natural gas purchases, if waste heat is 

recovered from generation and used for space and water heating; 

• Revenues from the sale of excess electricity to the local utility, or from 

the sale of methane gas (each requires additional costs);

• Avoided costs—or revenues from sales—of bedding made from digested 

solids;

• Avoided costs of commercial fertilizer and herbicides deriving from an 

improved fertilizer value of digester effl uent over raw manure; and

• Revenues from the sale of carbon credits in greenhouse gas markets.

We used ARMS Phase III data to analyze the avoided costs of electricity 

and fuel purchases on dairy and hog operations. Farm size matters. A typical 

Northeastern dairy farm with 200 cows spent nearly $29,000 on electricity, 

propane, and natural gas expenses in 2005, and that expense rose to $63,000 

on farms with 500 cows, and $114,000 on farms with 1,000 cows. Larger 

farms have a much stronger incentive to seek out investments that will allow 

them to replace purchased electricity, while small farms with digesters would 

need a market outlet for their electricity. But among farms of a given size, 

expenses can vary widely, and so can the incentives for digester adoption, 

with differences in farm production practices and location.

Location matters because prices for electricity vary across the country 

and variations in climate affect heating and cooling demand. In 2006, the 

average nationwide retail electricity price paid by fi rms in the commercial 

sector was 9.46 cents a kilowatt hour, but State-level averages ranged from 

5.16 cents in Idaho, the 4th largest dairy State, to 16.3 cents in New York, 
37

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

the 3rd largest.27 Propane and natural gas prices varied much less across 

States. Electricity and fuel usage can also vary because of differences in 

farm organization and technology.

Farms that milk three times a day use more electricity and fuel than those 

that milk twice a day, as do those with older milking systems. Farms that 

grow more crops, either for feed or for sale, use more electricity and fuel, 

holding herd size constant. Farms that use pasture for some of their forage, 

that raise heifers off-site, or that dry cows off seasonally, use considerably 

less, as do farms that keep cows in dry lots. 

The impact of these differences can be quite large. Farms in the Northeast 

and Western Corn Belt have substantially higher electricity, propane, 

and natural gas expenses than similarly sized farms in the West, South, 

and Eastern Corn Belt. If a typical 500-cow Northeastern dairy spent 

about $63,000 on those expenses in 2007, a dairy with 500 cows but with 

production practices more common for Western operations would spend 

about $28,000. Moreover, a Western operation with 1,000 cows would spend 

about $51,000, still well below expenses at a 500-cow Northeastern dairy.

Hog production has also shifted to much larger operations, but the way 

hog production is organized has also changed. Traditional farrow-to-fi nish 

operations, covering all stages of production, are being replaced with farms 

specializing in specifi c stages of production. As a result, the volume of 

manure per animal varies considerably, depending on the farm’s specialty. 

In addition, production is usually coordinated by an integrator that provides 

feed and feeder pigs to contract farmers, who grow the pigs to market 

weight. The farmer provides labor and capital services while the integrator 

retains ownership of the pigs and handles their disposition when they reach 

market weight. Integrators can have an important impact on adoption, both 

directly through their own actions and indirectly through the design of 

contracts with growers. 

Electricity and fuel expenses increase with the volume of hog production, 

so larger operations are likely to see greater gains from investment in 

digesters. The EPA estimates that digesters are economical for operations 

with at least 2,000 hogs, but conditions vary considerably, even among large 

operations. Some have deep-pit manure storage systems that would require 

costly retrofi tting for digester adoption. Avoided costs also vary widely across 

apparently similar operations. For a given number of market hogs produced, 

drylot operations have substantially lower electric and fuel expenses; farrowto-fi nish operations have substantially higher expenses than feeder-to-fi nish 

operations; and hog farms with signifi cant crop production have substantially 

higher electric and fuel expenses. Few fi nishing operations remove more than 

10,000 hogs/year, and electricity and fuel expenses for those with no crop 

production are unlikely to exceed $10,000. By contrast, those with substantial 

cropping operations may have expenses reaching $40,000-$50,000. As in 

dairy, location matters, with electric and fuel expenses substantially higher in 

eastern hog production States than in Corn Belt and Plains States.

There have been several other recent analyses of digester adoption. Leuer, 

Hyde, and Richard (2008) analyzed incentives for adoption on Pennsylvania 

dairy farms, and included the potential for additional revenues from sales of 

 27According to data from the Energy 

Information Administration, at 

http://eia.doe.gov.
38

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

electricity or carbon credits. Their analysis showed that larger operations were 

more likely to profi t from a digester, but their fi ndings suggested that farms 

would have to be quite large, on the order of 1,000 to 2,000 head. Profi ts from 

adoption were quite sensitive to the digester’s initial capital cost.28 Changes 

of 10 percent from a base case cost had large impacts on the profi tability 

of adoption, an important fi nding when estimates of capital costs still vary 

widely. 

Profi ts were also quite sensitive to the availability of revenues from the 

sale of electricity or carbon credits. Few large dairies would fi nd a digester 

investment to be profi table without signifi cant support for capital costs, 

carbon credit revenues, or revenues from electricity sales. To realize revenues 

from electricity sales, farms must connect their biogas-fi red generators to the 

electrical power grid, an action that raises safety, power quality, technical, 

legal, and procedural issues. Farms must often make additional capital 

investments to support connection, and they will often need to hire technical 

experts for information and guidance in negotiating contracts. Utilities are 

often reluctant to purchase excess electricity from farmers, and when they 

do are likely to offer rates refl ective of their avoided generation costs, which 

are generally well below retail rates. Opportunities to sell electricity are 

dependent on regulatory or legislative support in the State, so public policy 

will play a major role at the margin in driving adoption.

Farmers may qualify for carbon credits if they can capture methane and 

prevent it from emitting into the atmosphere. If farmers can provide credible 

claims of reduction in methane emissions, they may be able to sell the 

carbon credits in private transactions or in organized exchanges, thereby 

gaining further revenues from an investment in a digester. Credits traded 

on the Chicago Climate Exchange (CCX) varied over 2008 from $1.90 per 

metric ton to $7.40, with a mean price of $4.98 (Liebrand and Ling, 2008). 

If a lactating dairy cow produces fi ve metric tons of methane in a year (fi ve 

credits), then the farm could realize $25 per cow per year from the sale 

of carbon credits at a credit price of $5, and a farm with 1,000 cows could 

realize $25,000 in additional revenues. The farmer who had already invested 

in an anaerobic digester would bear some additional costs of qualifying for 

credits, for metering equipment and for fees paid to intermediaries, but the 

additional net revenues could make the project as a whole profi table. 

The costs to be borne by farmers for digester adoption, as well as the 

benefi ts accruing to them, are subject to considerable uncertainty. Stokes, 

Rajagopalan, and Stefanou (2008) examined the impacts of uncertainty 

on digester adoption among Pennsylvania dairy operations. They conclude 

that uncertainty can play a major role in deterring adoption, and that grant 

funding might be necessary to induce farmers who are uncertain about the 

value of the completed project to invest in digester adoption. 

Impacts on Fertilizer Uses for Manure

Only a small fraction of dairy manure is currently used for energy production 

through anaerobic digesters, with another small fraction in the CDP phase. 

If all current projects stayed in use, and all those in CDP phase were added, 

they would still account for less than 3 percent of the manure from dairy 

cows in the U.S. An even smaller share of hog manure is directed to energy 

 28USDA Rural Development has supported investments in anaerobic digesters 

through grants and loans. In the six years 

covering 2003-2008, USDA provided 

grants of $40.6 million, and loans of 

$19.1 million, in support of 121 digester 

projects. 
39

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

use through digesters. Less than 1 percent of fed cattle manure, and less than 

10 percent of turkey litter, is used in combustion energy processes, and we 

know of no current energy operations using broiler litter.

However, more large dairy and hog farms, and more contract poultry farms, 

could fi nd energy operations to be profi table options if energy prices were 

to rise, or if producers could realize additional revenue from the sale of 

electricity, gas, or carbon credits. Production is continuing to consolidate 

among larger hog and dairy operations for whom digester use is potentially 

feasible, and there could be a movement into digester use if the economics 

of the investment were to improve. Would a major shift toward energy 

production divert manure away from use as fertilizer?

Anaerobic digestion has one important feature that matters here: the N, P, and 

K fertilizer nutrients present in raw manure are retained in the effl uent from 

the digestion process. Digestion reduces pathogen counts and denatures weed 

seeds in raw manure, and the odors of raw manure are greatly reduced in the 

effl uent, thereby easing the storage, movement, and application of manure 

nutrients. As a result, anaerobic digestion may increase the fertilizer value of 

raw manure. 

Since the volume of liquid digester effl uent is unchanged from the amount of 

liquid in the raw manure entering the digester, the effl uent will still be costly 

to ship. 

Digesters are often used in combination with solids separators, although 

separators may also be used on farms without digesters. The liquid effl uent 

from separation is usually stored in lagoons and sprayed on crops as fertilizer. 

The solids may be used as bedding for cows, or they may be sold as compost 

to commercial and residential buyers. The nutrients that are retained in the 

solids are therefore lost to farming operations. However, it seems likely that if 

the solids had real value as crop nutrients, farmers would have used them as 

such instead of bearing the additional expense of turning them into compost.

Most nitrogen nutrients are burned during combustion processes. But the 

ash residues from combustion retain phosphorus and potash nutrients, in 

concentrated form because the process leaves about one pound of ash for 

every fi ve pounds of turkey litter. Combustion plants market the ash residue 

as fertilizer to farmers, and indeed Fibrominn located a fertilizer processing 

plant on site next to its generating facility. The transportation costs of the 

resulting fertilizer product are substantially reduced because of its lower 

weight and volume, which creates a larger market area for sales. 

The fertilizers derived from combustion processes might not be sold to 

farmers, and the nitrogen nutrients in the manure will be lost to crop 

fertilization, but local market forces play an important role here as well. 

Operators of combustion facilities purchase their manure feedstock, and 

operation will be most profi table in those areas with low prices for manure. 

Those are likely to be locations with excess manure nutrients and, therefore, a 

very low value for manure used locally. 
40

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Conclusions

Livestock manure has value for farmers because it contains nutrients that 

facilitate plant growth and because manure can improve soil quality by 

increasing organic matter, neutralizing acidity, and expanding the waterholding capabilities of soils. However, manure may not have the precise 

combination of nutrients needed for optimal crop production in a given 

fi eld. It is costly to move, and crops in modern agriculture may be produced 

at some distance from livestock. Manure odors may offend neighbors, and 

manure may contain a variety of pathogens.

Extent to which Animal Manure is Used as a Fertilizer

About 15.8 million acres of cropland, equivalent to about 5 percent of all U.S. 

cropland, are fertilized with livestock manure. This estimate is based on data 

drawn from several sources and is subject to some uncertainty. Nevertheless, 

it is clear that manure is used on only a small fraction of U.S. cropland. 

Patterns of manure use are driven by the agronomic needs of crops and by 

transport costs, which limit the distance that manure can be moved and 

create close links between types of livestock and certain crop commodities. 

In particular, dairy cow and hog manure tend to be collected in a slurry, and 

the high moisture content of slurry creates even higher transport costs. But 

the manure can be applied on-farm to corn; with its high nutrient uptake, 

particularly for nitrogen, corn is an attractive option for livestock operations 

seeking to utilize manure, and corn provides a livestock feed. As a result corn, 

which has accounted for about one-quarter of planted crop acreage in recent 

years, accounts for over half of the acreage to which manure is applied. 

In contrast, drier manure from poultry and cattle feedlot operations has 

lower transportation costs. Manure from those farms is more likely to be 

removed and shipped to other operations, and it is spread over a wider range 

of commodities. Because broiler production is concentrated in the southern 

United States, crops like peanuts and cotton rely heavily on broiler manure 

when they use manure fertilizers.

Potential Impact from Limitations Placed

on Use of Animal Manure

Livestock production has shifted to much larger operations, which also 

consolidate large quantities of manure in limited geographic areas. The 

quantities of manure nutrients produced on many large livestock operations 

exceed the capacity of the farm’s crops to absorb them, a problem that 

extends beyond individual farms to some regions where aggregate manure 

nutrient production exceeds the region’s crop nutrient needs. Excess nutrients 

can lead to water and air pollution.

In response to environmental risks, Federal, State, and local authorities are 

expanding their regulation of manure storage, transport, and application. 

Many operations now must prepare, fi le, and comply with detailed plans for 

managing manure so as to limit the possibilities for catastrophic spills or for 

land application in excess of the agronomic needs of crops. Some need to 
41

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

change manure management practices to comply with the plans. They will 

need to acquire more land for manure application, arrange with other farmers 

to accept manure for their cropland, reduce the nutrient content of manure, 

reduce manure production, or fi nd other uses for manure.

Estimated costs of compliance vary with the degree to which nearby farmers 

are willing to accept manure for application to their cropland, because a low 

willingness to accept among nearby farmers means that livestock producers 

will need to transport manure much farther for crop application. Costs also 

vary with the size and location of the operation, and with the particular 

type of nutrient management plan (standards may be set for nitrogen or for 

phosphorus). 

With a limited willingness to accept manure (defi ned as 20 percent of nearby 

farmers), production costs, including those for manure management, would 

likely rise by 2.5-3.5 percent for large operations (Ribaudo et al., 2003). Such 

costs are unlikely to alter the size structure of livestock production, where 

large operations have substantial cost advantages over small operations. 

They are also unlikely to lead to substantial declines in production and 

consumption; the resulting percentage increases in retail prices would be less 

than those noted above because farm costs are only a fraction of retail costs, 

and retail demand for meat and milk is relatively insensitive to price changes. 

As a result, expanded regulation through nutrient management plans will 

likely lead to wider use of manure on cropland, at higher production costs, 

with little impact on farm structure. 

Effects on Agricultural Production due to Increased 

Competition for Manure for Energy Production

There is widespread interest in using manure as a feedstock for energy 

production. Current examples include combustion power plants and anaerobic 

digestion systems designed to capture methane gas and burn it as fuel for 

electricity generation. While each technology is in commercial use in the 

United States, neither is widespread. Digester systems, either planned, in 

construction, or in operation, cover less than 3 percent of dairy cows and less 

than 1 percent of hogs. The single operating combustion plant utilizes litter 

from 6.6 percent of U.S. turkey production, while an idled plant in California 

could utilize manure from about 3 percent of fed cattle.

Farmers who produce electricity through digesters can benefi t from avoided 

purchases of electricity, but few can realize enough savings to justify the 

expense. Similarly, farmers can generate additional revenue from sale of 

manure to combustion plants, but few potential plant operators have found the 

economics to be attractive. But because such projects use existing resources, 

they could provide society with benefi ts if manure replaces newly mined 

fossil fuels in energy production, and if methane, a greenhouse gas, can be 

captured. Those societal benefi ts have led to proposals to support the use 

of manure for energy projects through State utility mandates (to purchase 

electricity from farms and to invest in renewable production sites), subsidies 

for capital costs, and direct subsidies and credits for energy production. 

Expanded support could lead to a substantial growth of energy applications 

for manure. In turn, that leads to a concern that expanded energy uses might 

compete with fertilizer uses for manure.
42

Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Energy projects are unlikely to impose substantive constraints on the use 

of manure as fertilizer, for two main reasons. First, the technologies do not 

consume the nutrients in manure that are benefi cial for plant growth. In the 

case of digesters, the nitrogen, phosphorus, and potassium nutrients remain 

in the effl uent of the digester process, to be spread on fi elds. To the extent 

that digestion eliminates manure odors and nearly eliminates pathogens 

in manure, the process may make neighboring farmers more willing to 

accept manure for cropland application. Combustion plants do burn nitrogen 

nutrients but leave the phosphorus and potassium in concentrated form in ash 

residues. Second, manure-to-energy projects function in markets for fertilizer 

and energy and will be most economical in those areas where the acquisition 

costs of manure are lowest. In turn, manure acquisition costs will be lowest 

where manure is in excess supply, with the least value as fertilizer.
43

Manure Use for Fertilizer and for Energy / Report to Congress

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Gollehon, Noel, Margriet Caswell, Marc Ribaudo, Robert Kellogg, Charles 

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Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Martin, John H. “An Evaluation of a Mesophilic, Modifi ed Plug Flow 

Anaerobic Digester for Dairy Cattle Manure.” Report submitted to the 

U.S. Environmental Protection Agency under Contract No. GS-10F0036K. July, 2005.

Martin, John H. “An Evaluation of a Covered Anaerobic Lagoon for Flushed 

Dairy Cattle Manure Stabilization and Biogas Production.” Report 

submitted to the U.S. Environmental Protection Agency under Contract 

No. GS-10F-0036K. June 2008.

Post, Tim. “Fibrominn Powers Ahead with Turkey Litter.” Minnesota Public 

Radio. June 18 2007.

Ribaudo, Marc, Noel Gollehon, Marcel Aillery, Jonathan Kaplan, Robert 

Johansson, Jean Agapoff, Lee Christensen, Vince Breneman, and Mark 

Peters. Manure Management for Water Quality: Costs to Animal Feeding 

Operations of Applying Manure Nutrients to Land. U.S. Department of 

Agriculture. Economic Research Service. AER-824. June 2003.

Stokes, J.R., R.M. Rajagopalan, and S.E. Stefanou. “Investment in a Methane 

Digester: An Application of Capital Budgeting and Real Options.” Review 

of Agricultural Economics 30(4)(2008): 664-676.

U.S. Department of Agriculture. National Agricultural Statistics Service, 

Acreage. June 2006.

U.S. Department of Agriculture. National Agricultural Statistics Service. 

Farms, Land in Farms, and Livestock Operations. February 2009.

U.S. Department of Agriculture. Natural Resources Conservation Service. An 

Analysis of Energy Production Costs from Anaerobic Digestion Systems 

on U.S. Livestock Production Facilities. Technical Note 1. October 2007.

U.S. Environmental Protection Agency. Market Opportunities for Biogas 

Recovery Systems: A Guide to Identifying Candidates for On-Farm and 

Centralized Systems. EPA-430-8-06-004. August 2004.
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Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Glossary

Anaerobic digester – Storage system that stores manure under anaerobic 

conditions (without oxygen). Under these conditions, decomposition of 

organic waste by bacteria results primarily in methane and carbon dioxide 

biogases. The gases can be burned to generate electricity.

Animal unit (or AU) - a standardized measure used in USDA statistical and 

regulatory programs to allow comparisons of manure production and feed 

needs across species. For example, some systems defi ne an AU to be 1,000 

pounds liveweight, so that four 250-pound hogs, or 200 5-pound broiler 

chickens, would each constitute one AU.

ARMS – Agricultural Resource Management Survey, an annual survey of 

farm fi nances and production practices that is carried out annually by the 

Economic Research Service and the National Agricultural Statistics Service.

Biogas – Gases produced by the biological decomposition of organic matter.

Broiler – Young chicken grown for meat.

CAFO – Concentrated animal feeding operation, a term developed by the 

Environmental Protection Agency for use in regulation. Animal feeding 

operations are agricultural operations where animals are kept and raised in 

confi ned conditions; feed is brought to the animals rather than the animals 

grazing or seeking feed in pastures, fi elds or rangeland. Concentrated 

operations meet certain additional EPA guidelines for operation size and 

proximity to water sources.

Commercial fertilizer – A substance, containing one or more recognized 

plant nutrients, that is designed to promote plant growth and that is 

manufactured from substances, such as natural gas or phosphate rock, that 

have been chemically altered. 

Corn silage – Corn silage is a high-energy feed, used primarily for 

ruminants like cattle or sheep, that is created from fermentation of the entire 

green plant (and not just the grain).

Crop nutrients – Sixteen chemical elements are known to be important to 

plant growth and survival. Three—hydrogen, oxygen, and carbon—are nonmineral nutrients while the other thirteen are minerals. Among the minerals 

are three primary macro-nutrients: nitrogen (N), phosphorus (P), and 

potassium (K). Primary macro-nutrients are often lacking in the soil because 

plants use large amounts for growth and survival, and they hence are often 

provided through fertilizers. 

Dairy cow – Female cow that has had her fi rst calf and is used to produce 

milk commercially. 

Dry cow – A dairy cow who is not producing milk. Typically, a farmer will 

stop milking a cow for the two months prior to an upcoming birth, in order to 

relax her and build up strength for the birth.
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Manure Use for Fertilizer and for Energy / Report to Congress

United States Department of Agriculture

Farrow-to-feeder – Hog operation that contains breeding females (sows) and 

that raises pigs from birth until they are weaned and attain a feeder weight of 

30-80 pounds.

Farrow-to-fi nish – Hog operation that contains breeding females and that 

raises pigs from birth to a slaughter weight of 225-280 pounds.

Fed cattle – Beef cattle fed for slaughter in specialized operations called 

feedlots. Most beef cattle are raised on pasture, fi elds, and rangeland before 

being shipped to feedlots, and some are raised to slaughter weight without 

being shipped to feedlots.

Feeder-to-fi nish – Hog operation that takes feeder pigs of 30-80 pounds and 

feeds them to a slaughter weight of 225-280 pounds.

Feedlot – Beef cattle operation that take young cattle, weighing 400-800 

pounds, and feeds them to a slaughter weight of 1100-1300 pounds. Feedlot 

cattle are confi ned in pens and fed specialized diets of grains, oilseed meals, 

and other nutrients.

Heifer – Young female cow who has yet to give birth. Heifers may be used 

as replacement cows for beef or dairy production, or they may be fed to 

slaughter weight and used only for beef production.

Integrator – A fi rm or farm that contracts with other farms to raise livestock 

or poultry for it. Integrators typically provide young livestock or poultry 

and feed to the farm; they may sell the mature animals to processors, or the 

integrator may also operate processing facilities. 

Litter – Poultry litter consists of poultry manure; bedding material such as 

sawdust, sand, wood shavings, or straw; and feathers and spilled feed. 

Manure – Organic matter derived from animal production, which includes 

feces, urine, hair or feathers, and blood. Usually used as plant fertilizer, 

although it can also be used as a feedstock for power generation, and 

processed manure may be used as bedding for livestock.

Methane – A chemical compound with the molecular formula CH4. The 

principal component of natural gas, it is also a relatively potent greenhouse 

gas with a high global warming potential. Livestock, primarily cows, are a 

source of methane. 

NMP – A nutrient management plan, which specifi es a set of information 

and conservation practices designed to use commercial fertilizers and manure 

effectively while protecting against the potentially adverse effects of nutrient 

storage and application and water and air quality.

Steer – Castrated male cattle, typically used for beef production.

Weanling to feeder – Hog operation that takes just-weaned pigs and raises 

them to a feeder weight of 30-80 pounds.