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FY 2009 Annual Report

National Program 206—Manure and Byproduct Utilization

Introduction

According to the National Agricultural Statistics Service, over one billion tons of 

agricultural (e.g., manure), municipal (e.g. biosolids), and industrial (e.g. coal 

combustion products) wastes with potential uses in agriculture are generated annually in 

the United States. Many of these materials are spread, sprayed or otherwise applied to 

agricultural land because of the benefits they provide. These benefits include: providing a 

nutrient source for crops; improving soil chemical, physical and biological properties; 

improving soil water storage and use; reducing movement of contaminants to water and 

air; and reducing production costs and energy use. However, improperly managed 

manure and other byproducts can pose a threat to soil, water and air quality, and to 

human and animal health.

The goal of the Agricultural and Industrial Byproducts National Program is to develop 

and evaluate management practices and systems, control technologies, and decision tools 

to allow producers and their advisors to (1) use manure and other byproducts effectively 

and safely while protecting the environment and human and animal health and (2) 

provide policy-makers and regulators with information and tools to establish appropriate 

conservation and environmental credit trading programs, and make environmental 

protection decisions. To achieve this goal, this National Program is focused on four major 

areas of research: atmospheric emissions, nutrient management, pathogens and 

pharmaceutically active compounds, and municipal and industrial byproducts. 

Sustainable agriculture depends on effective management of manure and byproducts. 

Selected accomplishments from these four components are described in the following 

section.

Atmospheric Emissions: Air emissions from animal production operations and land 

application of manure and other byproducts include particulate matter, ammonia, volatile 

organic compounds (that cause odor or serve as precursors for ozone formation), 

hydrogen sulfide, greenhouse gases and pathogens. Research is being conducted to: (1) 

develop new methods and improve existing methods to measure particulate matter and 

gaseous emissions; (2) develop and determine the effectiveness and environmental 

benefits of management practices and control technologies to reduce emissions; and (3) 

develop and test decision tools to predict emissions and their dispersion across a range of 

animal production systems, management practices, and environmental conditions. Tools 

and practices for measurement, control and prediction of emissions from animal 

production operations will help provide the scientific background for management, policy 

and regulatory decisions.
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Selected Accomplishments

Development of a green and profitable manure treatment technology. New or 

expanding swine production facilities in North Carolina are required to use manure 

management systems that meet the strictest environmental performance standards in the 

nation. A second-generation system was developed by ARS-Florence scientists and 

cooperators that met state environmental standards for manure management. The new onfarm treatment system uses solid-liquid separation and nitrogen and phosphorus removal 

processes (U.S. Patent Application US 2008/0314837) to remove high levels of several 

pollutants from manure wastewater, including almost all of the pathogens, odor-causing 

constituents, and ammonia. Replacing anaerobic-lagoon-based systems with this new 

technology reduced greenhouse gas emissions by 97 percent. Animal health and 

production also benefited. Swine daily weight gain increased, feed conversion improved, 

animal mortality decreased, and 5.6 percent more hogs were sold per growing cycle. In a 

centralized facility, separated manure solids were converted to composted materials and 

used for organic plant fertilizer, soil amendments, and plant growth media. Through 

these innovations and on-farm testing, significant cost reductions were achieved. This 

revamped system was two-thirds less expensive to build and operate than the firstgeneration system (tested in 2003). Producers can also profit from this new system by 

selling both greenhouse gas emission reduction and water quality credits. 

Fate of odorants from animal feeding operations is as important as emission rates. 

The National Research Council has identified odors as the most significant animal 

emission problem at the local level. In a large collaborative study with ARS-Ames, 

Kansas State University, and ARS-Beltsville, the concentrations of odorant compounds 

were determined at several distances from a large cattle feedlot in Kansas. Results 

showed that volatile fatty acids (VFAs), indole (a nitrogen aromatic compound), and 

phenols were most prevalent at the feedlot, but that VFAs were much less important two

miles from the lot. This suggests that mitigation strategies that only focus on controlling 

the rate of emissions from farms will not necessarily solve downwind nuisance odor 

problems. The fate of each chemical once it is released into the atmosphere must be 

considered and the detection threshold of each chemical relative to its concentration are 

both needed to prioritize odor reduction efforts and to evaluate the effectiveness of best 

management practices.

Remediating Odor from Livestock Waste. Malodors from confined animal feeding 

operations are a source of complaints and may have adverse environmental impacts. 

ARS Scientists from Bowling Green, KY, and Florence, SC, studied reductions in 

malodor effected by a second generation wastewater treatment plant during three cycles 

of pig rearing. The wastewater treatment system consisted of three modules: solids 

separation, biological nitrogen removal, and phosphorus recovery/wastewater 

disinfection. While approximately 90% of the wastewater solids were removed in the first 

stage of treatment, little reduction in malodorous compounds occurred, indicating that 

malodorous compounds largely remained with the liquid waste stream. The greatest 

improvements in wastewater quality occurred in the nitrogen treatment module, where 

malodorous compounds were reduced by more than 90% as compared to the raw flushed 
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manure. The system consistently achieved high performance standards, even during the 

first cycle of livestock production when system performance was being optimized. 

Combining two simple processes into a practical treatment system can be very effective 

in reducing malodorous compounds from livestock wastewater.

Field assessment of Nitrous Oxide (N2O) emissions from manure applied to soil. 

Nitrous oxide (N2O) is a greenhouse gas that is many times more potent than carbon 

dioxide in terms of global warming potential. Agriculture is the largest human-related 

source of nitrous oxide emissions. ARS scientists studied the temporal patterns of N2O 

emissions following addition of swine manure slurry under fluctuating soil moisture 

regimes, assessed the potential of a rye cover crop to decrease N2O emissions under these 

conditions, and quantified field N2O emissions in response to either spring applied 

conventional nitrogen fertilizer or different rates of fall-applied liquid swine manure, in 

the presence or absence of a rye/oat winter cover crop. Results showed a significant 

reduction in N2O emissions in the presence of the rye cover crop. Nitrous oxide 

emissions were evaluated at three swine manure application rates and with spring applied 

fertilizer, in the presence or absence of an oat/rye cover crop. The primary factor 

influencing N2O emission was nitrogen (N) application rate, regardless of form or timing. 

The response of N2O emission to N additions was non-linear, with an increasing 

proportion of the applied nitrogen being emitted as N2O as total N application rates were 

increased. These results indicate that while cover crops have the potential to reduce N2O 

emissions, N application rate may be the overriding factor, thus emphasizing the need for 

careful N application management practices.

Ammonia Emissions from Beef Cattle Feedyards. A recent ruling by the 

Environmental Protection Agency (EPA) required cattle feeders to report ammonia 

emissions under the Emergency Planning and Community Right-to-Know Act (EPCRA). 

At the request of the Texas Cattle Feeders Association, ARS researchers at the 

Conservation and Production Research Laboratory, Bushland, Texas, led a group of 

scientists from ARS and Texas AgriLife Research that compiled the state-of-the-science 

of ammonia emissions from cattle feedyards. This report was used by the National 

Cattlemen's Beef Association (NCBA) to develop a worksheet used to estimate feedlot 

ammonia emissions that could be used to meet EPCRA reporting requirements. The 

worksheet was delivered online, in newsletters and through an online webinar to NCBA 

affiliates, which reached about 85% of the cattle feeding industry and allowed the cattle 

industry to meet the regulatory reporting requirements, despite a very short deadline.

Developing Emission Factors for Open-lot Dairies in Southern Idaho. In Idaho, the 

number of dairy cows has increased by approximately 88% in the last decade with 

concentrated dairy production facilities being the norm, generating environmental 

concerns related to regional air quality. Ammonia, methane, carbon dioxide, and nitrous 

oxide emissions were determined on a 10,000 milking cow open-lot dairy in southern 

Idaho. This work was performed by ARS scientists at the Northwest Irrigation and Soils 

Research Laboratory (NWISRL), Kimberly, Idaho. Emissions were determined for 

several days each month over the course of a year at three locations: the cattle pens, 

lagoon, and compost areas. This study reports some of the first ammonia, methane, 
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carbon dioxide and nitrous oxide emissions data from a large scale open lot dairy 

production facility that encompasses both daily and seasonal variations in emissions and 

will provide preliminary data for the development of emissions factors from this type of 

production facility. Emissions factors will be used to estimate atmospheric emissions 

from producers operations for proposed EPA permit/regulatory purposes.

Nutrient Management: The utilization of nutrients in manure in an environmentally 

sustainable manner is one of the critical management issues facing livestock producers. 

Movement of nutrients in excess amounts from manure and other byproducts to soil, 

water and air can cause significant environmental problems. Nitrogen and phosphorus 

from manure and other sources have been associated with algal blooms, accelerated 

eutrophication of lakes and streams, and development of hypoxic zones in the Gulf of 

Mexico. ARS scientists are conducting research to develop management practices, 

control technologies, and decision tools for effective agricultural use of nutrients from 

manure and other byproducts, while protecting environmental quality and public health.

Selected Accomplishments

Poultry Litter is Superior to Commercial Fertilizers for Cotton. Increasing 

conventional fertilizer costs and the local availability of poultry litter pose questions 

about the potential value of poultry litter as a fertilizer source for cotton producers. ARS 

Genetics and Precision Agriculture Research scientists at Mississippi State, MS, found 

poultry litter to be superior to conventional inorganic fertilizers in certain marginally 

productive upland soils. On soils that historically have low productivity, cotton fertilized 

with raw litter produced up to 26% more lint than cotton fertilized with conventional 

inorganic fertilizers. In soils that are considered more productive, poultry litter and 

conventional fertilizers had comparable effects on cotton lint production. Thus poultry 

litter has the potential to replace many of the commonly used and more expensive cotton 

fertilizers in all soils, increasing the profitability of cotton production in the southern and 

southeastern states.

Benefits of Shallow Subsurface Band Application of Poultry Litter. Poultry litter is 

typically land-applied by broadcast surface application, but this method has a high 

potential for undesirable transport of litter nutrients off the field into streams, rivers, 

lakes, and other bodies of water. An experimental four-trench litter applicator field 

implement that applies litter in shallow subsurface bands in soil was used in five field 

experiments. When the poultry litter was applied in subsurface bands, phosphorus and 

nitrogen concentrations in water running off field plots were reduced by 80 to 95% 

compared to traditional broadcast surface application. Use of the implement by 

producers and others who apply litter to fields is expected to reduce pollution of streams, 

rivers, lakes, and other bodies of water, while maximizing the nutrient value of the litter 

to farmers.

Management recommendations for temporary storage of poultry litter. Temporary 

in-field storage piles of poultry litter are commonly used in the mid-Atlantic region due 
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to a shortage of on-farm litter storage and the desire to transport and disperse the litter to 

more distant areas which have not been heavily manured. A ten member technical expert 

panel of ARS, NIFA, and industry scientists reviewed the literature on temporary storage 

piles of litter and developed a set of recommendations for using this in-field storage 

technique. The findings and recommendations include: minimizing the need for using infield storage by increasing on-farm storage, using an “A” shaped pile to minimize the pile 

footprint and runoff, locating piles on well-drained level land distant from surface waters 

with site location changed each year, allowing piles to remain intact until just before 

spreading because the greatest nutrient losses occur after land application, develop soil 

and agronomic practices for remediation of the stockpile footprint, and encouraging land 

application that includes shallow incorporation or injection. These recommended 

management practices will conserves nutrients for the producer and minimize nutrient 

losses to the Chesapeake Bay and elsewhere.

Diets Including Forages for Developing Replacement Heifers Require No 

Supplementation of Phosphorus. When phosphorus (P) is fed to cattle in amounts 

greater than they can utilize, the excess is excreted in the manure. If phosphorus-rich 

manure is later spread on farm fields to provide nutrients for growing crops, it can also 

cause an excess of phosphorus in runoff that promotes the growth of undesirable algae in 

receiving aquatic systems. Phosphorus is essential for bone growth and development in 

growing dairy heifers. The amount of dietary phosphorus needed in dairy heifer diets is 

very similar to that found naturally in many forages comprising typical heifer diets. 

Scientists from the University of Wisconsin-Madison and the U.S. Dairy Forage 

Research Center conducted a long-term trial on phosphorus supplementation with heifers 

ranging from 4 to 22 months of age. Heifers were fed diets with or without supplemental 

phosphorus resulting in dietary phosphorus concentrations of 0.29 or 0.39%. Results 

showed that phosphorus supplementation for developing replacement heifers had 

minimal effect on the extent of frame development, bone density, or bone metabolism. A 

parallel experiment evaluating runoff from simulated rain on applied manures from 

heifers showed that incorporating manure reduced P losses in runoff by 85-90%, and that 

manure from heifers fed unsupplemented diets resulted in lower P concentrations in 

runoff than those fed P-supplemented diets. This information will help dairy producers 

and nutritionists formulate heifer rations that contain adequate, but not excessive, 

amounts of phosphorus, so that the growth needs of the heifers are met without adding 

excess phosphorus to the environment.

An updated website at Cornell is improving whole-farm nitrogen management. 

Nitrogen management on Northeast dairy farms is a challenge because of the range of 

farm-grown feeds, the wide array of manure management systems, and the wide range of 

field crops and soils across the region. Cooperative research among several Northeast 

Land-grant Universities and ARS scientists in Beltsville has provided an on-line nitrogen 

management tool describing best management practices for dairy farms that utilizes a 

whole-farm perspective. The web site, http://www.dairyn.cornell.edu/, was updated and 

now contains components on concerns about nitrogen losses, crop and soil nitrogen 

management, feed storage nitrogen management, dairy herd nitrogen management 

including precision feeding, manure storage nitrogen management, and integrating the 
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above components into a whole-farm system. The web site has been written up in several 

popular press articles and is an important resource for Extension agents, dairy 

consultants, USDA-NRCS (Natural Resources Conservation Service) agents, and nutrient 

managers as they develop site-specific whole-farm nutrient management plans for 

Northeastern dairies.

Snap-shot Assessment of Nutrient Use Efficiency on Confinement Dairy Farms. 

Nutrient use efficiency can be broadly defined as the relative amount of feed, fertilizer 

and/or manure nutrients inputs that are incorporated into milk, crops/pasture or other 

outputs. Relatively little information is available on nutrient use efficiency on 

commercial dairy farms, or on how it can be measured and evaluated for impacts on 

profitability and environmental performance. Over the past several years, researchers at 

the U.S. Dairy Forage Research Center and the University of Wisconsin-Madison have 

developed tools that can be used to provide snap-shot assessments of feed, fertilizer, and 

manure use on dairy farms in various settings. A website was developed that contains (1) 

a Fact Sheet giving an overall explanation of nutrient use efficiency, the importance of 

knowing it, and how to measure it; (2) a Nutrient Management Survey questionnaire; (3) 

a Manure Spreading Book – a document to help dairy producers keep track of when, 

where, and why they spread manure; (4) an example of a Final Farmer Report; and (5) 

four scientific journal articles related to nutrient use efficiency on confinement dairy 

farms. Snap-shots tools and their results have been used (1) to develop recommendations 

about how to integrate dietary, livestock management, and manure handling practices 

into comprehensive nutrient management programs, and (2) to identify management 

practices that bring dairy farms into better nutrient balance while maintaining farm 

productivity and profitability. They have been adapted for use by (1) extension educators 

involved in nutrient use training, (2) decision-makers working to develop guidelines and 

regulations for improving nutrient management, and (3) university students, many of 

whom will be researchers, conservation program staff, or consultants assisting dairy 

farmers with nutrient management in the future.

Pathogens and Pharmaceutically Active Compounds: Pathogens and pharmaceutically 

active compounds in manure, biosolids, and other byproducts can be transmitted to 

animals and humans through food supplies, water and possibly air. Livestock and poultry 

can also be re-infected not only via water and air, but from other vectors such as birds, 

rodents and insects. The most significant of the manure-borne zoonotic pathogens are the 

protozoan parasites Cryptosporidium parvum and Giardia duodenalis, and the bacterial 

pathogens Salmonella, Campylobacter, Escherichia coli, and Listeria monocytogenes. 

Pharmaceutically active compounds such as hormones and antibiotics may also be 

present in animal waste and disseminated in the environment. The potential for serious 

health effects both on and off the farm, the lack of knowledge about pathogen survival in 

manure during collection, storage, treatment and application, and uncertainty about fate 

and transport of pathogens in soil, water and air from the animal production site or 

manure application area, clearly point to the need for research on these issues.
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Selected Accomplishments

Determining the concentrations of hormones in biosolids and poultry litter. The 

presence of natural hormones and the synthetic hormone ethinylestradiol was monitored 

in lime-treated biosolids and poultry litter samples in order to determine the likely 

potential of these compounds to run off from fields treated with these materials as soil 

amendments. These hormones exist in their free form and as chemical conjugates 

requiring more sophisticated measurement techniques such as liquid chromography triple 

quadrupole mass spectrometry. Estrone, estrone sulfate, and progesterone were found 

most frequently, with the concentrations in biosolids typically less than 10 ng/g.

Concentrations in poultry litter were somewhat higher. Estriol, estradiol, ethinylestradiol, 

and testosterone were seldom detected. This information can be used to design costeffective treatments to reduce the concentrations of these compounds in land-applied 

biosolids and litter as well as more focused monitoring programs to insure that these 

compounds are not transported off site and into waterways.

Measurement of the environmental fate of hormones in poultry litter. Poultry litter 

contains the reproductive hormones estradiol and testosterone. These are endocrine 

disruptors that have been detected in surface waters worldwide. The objective of this 

study was to evaluate the potential impact of poultry litter applications on estradiol and 

testosterone concentrations in subsurface drainage and surface runoff in irrigated crop 

land under no-till and conventional-till management. The differences between no-till and 

conventional-tillage appeared to be related to variation in hydrologic transport for the two 

tillage systems. Although differences were observed between tillage practices, the 

application of poultry litter at rates set by the nutritional requirements of the crop appears 

to have little potential of contaminating surface and subsurface waters with these 

hormones. This is important information for the poultry industry and environmental 

protection agencies because surface waters contaminated with hormones from poultry 

litter are likely an indication of inappropriate or mismanagement of litter applications.

Determining the fate of antimicrobials in agricultural lands receiving biosolids. The 

antimicrobial pesticides, triclosan and triclocarbon, are often found in soap, detergents, 

and antiseptics, and have been found in biosolids from waste water treatment facilities. 

These compounds, which are highly toxic to aquatic organisms, are strongly sorbed to 

biosolids, but can be released to the environment when biosolids are applied to 

agricultural fields. Studies were conducted to determine the likely concentrations of 

triclosan and triclocarban in biosolids by examining their sorption to biosolids during 

treatment of waste water and then following their fate in land applied biosolids, a major 

(60%) disposal practice in the U.S. Concentrations in fresh biosolids averaged 16 and 18 

mg/Kg, respectively for triclosan and triclocarbon; the half life of triclosan after biosolids 

application was more than 100 days, and many times longer for triclocarban. The 

persistence of these compounds means that more research on the factors controlling the 

release of these compounds from land-applied biosolids and their potential transport 

offsite is needed to minimize negative effects to surrounding ecosystems.
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ARS participates in an interagency task force on pharmaceuticals in the 

environment. An interagency report, “Pharmaceuticals in the Environment: An 

Interagency Research Strategy” was completed with ARS as a work group member. This 

report was commissioned by the Committee on the Environment and Natural Resources, 

Office of Science and Technology Policy. The purpose of this report was to summarize 

federal research in this area and to develop an integrated interagency strategy for 

conducting investigations on priority research needs identified by the work group. The 

following outcomes from this planning document are being implemented: 1) coordinate 

animal feeding operation studies to examine the contribution of pharmaceuticals to the 

environment combined with exposures from waste water treatment plant discharges; 2) 

organize an analytical user’s group; and 3) highlight the stewardship activities in USDA 

and coordinate USDA National Institute for Food and Agriculture (NIFA) granting 

efforts into the research plan.

Variations of fecal indicator bacteria in a large urban watershed. Data from the 

Santa Ana River watershed, Southern California, USA demonstrate that both existing and 

Environmental Protection Agency (EPA)-recommended water quality criteria for 

allowable bacteria levels are routinely exceeded in this watershed, often by one or more 

orders of magnitude. Total coliform (TC), fecal coliform (FC), E. coli, enterococci, and 

total bacterial concentrations were monitored by ARS scientists at Riverside, CA in 13 

locations in the watershed over a two year period. Bacterial count estimates changed far 

more significantly across different sites, in comparison to seasonal flow estimates or 

estimates across time. These results imply that TC, FC, E. coli, and enterococci bacterial 

counts in the two tributaries are strongly influenced by spatial location, with 

contamination due to local agricultural and/or urban run-off as opposed to elevated upstream contamination and/or discharge contamination associated with the two wastewater 

treatment plants (WWPT). Therefore, this study has provided useful information that can

be used in constructing watershed management plans for a mixed use watershed.

Assessing the diversity in cell properties and transport behavior among 12 different 

environmental Escherichia coli isolates. Escherichia coli (E. coli) is a common fecalborne pathogenic microorganism in water supplies. The importance of E. coli as an 

indicator organism has led to numerous studies looking at cell properties and transport 

behavior of this microorganism. In many of these studies, however, only a single strain of 

E. coli was used even though research has shown a significant amount of genetic 

variability exists among different strains of E. coli. If this genetic diversity results in 

differences in cell properties that affect transport, different strains of E. coli may exhibit 

different rates of transport in the environment. Research was conducted at the ARS 

Animal Waste Management Unit in Bowling Green, KY, in collaboration with the 

University of California – Riverside, to assess the variability in surface characteristics 

and transport behavior of E. coli isolates obtained from six different sources. Results of 

this study showed that a large diversity exists in cell properties and transport behavior for 

the different E. coli isolates. Because USEPA recommends the use of E. coli as an 

indicator of fecal contamination in freshwater systems, its fate and transport in the 

subsurface needs to be better understood. This study shows that generalizations about the 

transport behavior of E. coli based on results from a single strain of E. coli should be 
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made with caution. In addition, this large variability suggests that the modeling of E. coli 

in the environment will require a distribution of bacterial attachment rates, even when

modeling E. coli movement from a single fecal source.

Identifying the sources of fecal contamination. Fecal contamination of recreational, 

drinking and fishing waters is a major global problem. Detecting and ranking the sources 

of fecal pollution is challenging as common methods used cannot discriminate among the 

sources. A method for Microbial source tracking (MST) was tested utilizing four genetic 

markers specific for ruminants to identify the animal source and origin of fecal pollution. 

Identifying sources of fecal contamination is important because it is the first step in 

stopping the source. This project investigated two watersheds with different management 

histories. In the watershed impacted by cattle the four genetic markers specific for cattle 

were detected in 32 to 65% of the DNA extracted from water and sediment samples. In 

contrast, at the site not impacted directly by cattle, the genetic markers were detected in 

only 6% of the water samples. The detection of the genetic markers was correlated to the 

abundance of the fecal indicator bacteria fecal enterococci. This emerging MST approach 

removes subjectivity, and offers potential for identifying, tracking, and characterizing 

fecal sources and reservoirs, provides a tool for remediation and enforcement.

Byproducts: Each year millions of tons of agricultural, municipal and industrial 

byproducts are generated in the United States. These materials are frequently considered 

to be wastes and are often disposed in landfills. However, many of these materials have

characteristics that make them potentially useful to improve soil properties for enhanced 

crop production, to prevent movement of contaminants to critical bodies of water, and to 

lower energy inputs in agricultural systems. Research is being conducted to determine 

benefits and risks of the materials, to develop and evaluate the effectiveness and 

economic benefits of byproduct-based management practices and control technologies, to 

document the environmental benefits of using these materials, and to develop guidelines 

for specific uses.

Selected Accomplishments

Benefits of flue gas desulfurization (FGD) gypsum. Degraded soils result in reduced 

crop yields, require higher inputs of fertilizer, water and energy, and pose a greater threat 

to the environment than high quality soils. Many of the agricultural, industrial and 

municipal wastes generated each year may be appropriate soil amendments to improve 

degraded soils. ARS scientists from several locations (West Lafayette, Indiana; Oxford, 

Mississippi; Tifton, Georgia; and University Park, Pennsylvania) have demonstrated that 

flue gas desulfurization (FGD) gypsum, generated by removal of sulfur dioxide from the 

flue gases of coal-fired power plants, can improve soil chemical and physical properties 

and reduce contaminant movement to surface water. Their research has shown that 

application of FGD gypsum to soil improves soil structure, resulting in greater infiltration 

and storage of rainwater. Since water moves into the soil, more is available for 

subsequent use by crops and less runs off the soil surface, reducing erosion and the 

movement of sediment, nutrients and trace elements to surface waters. More efficient 
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infiltration and storage of rainfall is critical to crop production in areas that have recently 

experienced severe drought, such as the southeastern United States. These results show 

that a low-cost material like FGD gypsum can allow farmers to increase crop production 

while improving soil and water quality. The southeastern United States alone has 

approximately 20 million acres of crop and pasture land that could benefit from 

application of FGD gypsum.

Impact of Gypsum Applied to Grass Buffer Strips on Reducing Soluble P in Surface 

Water Runoff. Due to environmental concerns, improved methods to reduce 

phosphorus loading to surface waters associated with animal production are needed. 

Studies to evaluate the use of gypsum as a soil amendment to reduce losses of 

phosphorus from poultry litter in forage based production systems were conducted by 

ARS scientist in Auburn, AL. The project used rainfall simulation studies to quantify the 

potential for gypsum to reduce phosphorus in surface water runoff. Gypsum applied to 

grass buffer strips was effective in reducing soluble P concentrations (32–40%) in surface 

runoff , while the untreated buffer strip was somewhat effective in reducing soluble P 

(18%). Results indicated that gypsum could be used in filter strip areas where animal 

manures are utilized, to reduce environmental degradation due to excess phosphorus.

Increasing biogas production by digesting manure and pulped food wastes. Due to 

economies of scale, most dairy producers are currently unable to take advantage of 

anaerobic digestion to treat their animal’s waste and produce energy for farm use or sale 

to others. Simultaneously, there is growing interest in diverting organic wastes from 

landfills to minimize landfill methane emissions. ARS scientists anaerobically digested 

mixtures of dairy manure and pulped food to determine how biogas yields were affected 

by increasing amounts of food wastes. Results showed that reactors containing manure 

and 5% food waste produced about 20% more biogas than comparable reactors 

containing only 1% food waste. In addition to increasing biogas yield, on-farm digestion 

of food wastes with manure may provide opportunities for additional revenue through 

payments from food waste generators and carbon credits. By taking advantage of nearby 

wastes that would otherwise be destined for a landfill, smaller dairies might be able to 

economically treat their manure while developing new sources of revenue, increasing 

both long-term profitability and resilience to market fluctuations. 

Increasing biogas production by digestion of manure switchgrass in high-solids 

reactors. Although small dairy farms (less than 1000 animals) do not generate enough 

manure for economic electrical production from biogas, there are opportunities to 

combine other byproducts with the manure to increase biogas production significantly. 

ARS scientists in Beltsville, Maryland, anaerobically digested mixtures of three animal 

manures (swine, poultry, and dairy) and switchgrass to determine which mixture yielded 

the most biogas. Biogas yields were very low using high-solids reactors containing a 1 to 

5 ratio of dry switchgrass mixed with either dairy manure or diluted poultry litter. 

However, biogas production was relatively high from reactors using a comparable swine 

manure-switchgrass mixture. In these reactors, approximately 80% of biogas production 

was attributable to degradation of the switchgrass. Although these experiments are only a 
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first step in the process, the results suggest that switchgrass could be a useful biomass 

resource for high-solids digestion.

Old tires are an effective slow release zinc fertilizer. Waste rubber tires are a 

significant disposal problem in all states, containing about 1.5% zinc, added to rubber to 

speed vulcanization. Zinc is also a required micronutrient for crop production; some soils, 

particularly in the western U.S., require the addition of zinc fertilizer. Ground rubber was 

found to operate as a low grade or slow release zinc fertilizer. In addition, acid extraction 

of zinc from ground rubber tires produced both a zinc fertilizer for hydroponic production 

and a lower zinc ground rubber for use as a rooting medium for hydroponic production. 

No zinc toxicity was observed. Recycling old tires in this way provides a needed 

inexpensive fertilizer for producers while providing an economically valuable use for the 

hundreds of millions of waste tires generated each year in the U.S.

Safe use of spent foundry sands as a soil amendment. Each year, up to 10 million tons 

of spent foundry sands (SFS) are generated in the U.S. which are destined for disposal in 

landfills due to their assumed toxicity, but tests of SFS as a soil amendment showed that 

they did not pose a toxicity risk to either plants or earthworms. A comprehensive risk 

assessment, conducted in cooperation with U.S. EPA, revealed that spent sands from the 

iron, steel, and aluminum casting industries, were low enough in trace element and toxic 

contents that they could be safely used as soil amendments or as a component of 

manufactured soils. The assessment [submitted for peer review by US-EPA] considered 

multiple exposure routes to humans, livestock, wildlife, and soil organisms. Compared to 

the disposal of SFS in landfills, use of SFS in both agriculture and horticulture will 

provide significant environmental benefits as well as savings to numerous industries.

Grasses can remediate soils contaminated with TNT residues. TNT (2,4,6-

trinitrotoluene) is a persistent contaminant present in high concentrations on some 

industrial and military sites. Studies were conducted to evaluate the use of several 

grasses, tall fescue, perennial ryegrass, and orchard grass, to remove TNT from the soil in 

a process known as phytoextraction. Results showed that TNT accumulated in the plant 

shoots during each harvest, period and that the residues were incorporated in plant 

tissues, thereby eliminating any environmental risk. This work suggests that the overall 

soil TNT bioremediation goal can be achieved by using multiple grass harvests.

Mixed compost system removes lead and copper from building and parking lot 

runoff. Some building and parking lot materials will leach lead and copper during rain 

events which can contaminate nearby waterways. Holding ponds are used to capture this 

runoff but remediation of the water is still needed in some cases. A study was conducted 

to test a mixture of composted food waste, yard debris, and steel slag in a filtration 

system. Laboratory simulations showed that this mixed compost removed lead and 

copper to levels well below surface water discharge limits. The alkaline steel slag 

neutralized the acidity generated by reaction of lead and copper with the compost and 

allowed the compost filter to remain effective much longer than a filter without the steel 

slag. Thus, this mixed compost, when placed in a large scale filtration system, should
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provide an inexpensive, highly effective approach for removing metals in runoff, and 

protecting nearby waterways.