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United States Department of Agriculture

Agricultural Research Service


Location: Sustainable Agricultural Systems Laboratory

2011 Annual Report

1a. Objectives (from AD-416)
Development and evaluation of manure treatment systems. Specific objectives: (1) Develop treatment technologies and management practices to reduce the concentrations of pharmaceutically active compounds (antibiotics and natural hormones) in manures, litters, and biosolids utilized in agricultural settings; (2) Develop management practices and technologies to minimize greenhouse gas (GHG) emissions from manure and litter storage and from composting operations by manipulating the biological, chemical, and physical processes influencing production and release of ammonia and greenhouse gases during composting; (3) Develop technology and management practices that improve the economics and treatment efficiency of anaerobic digestion of animal manures and other organic feedstocks (e.g. food wastes, crops/residues) for waste treatment and energy production.

1b. Approach (from AD-416)
Modern livestock production involves the use of large amounts of nutrient inputs as well as antibiotics. Untreated manure is either stored or immediately applied to farmland as a fertilizer. When manure is applied to fields, manure components (nutrients, microorganisms, and remaining antibiotic residues) may reach surface water by volatilization, run-off or leaching. The goal of this research is to improve our basic understanding of two common manure treatment practices (composting and anaerobic digestion) so as to maximize their benefits and minimize their economic and environmental costs. The first objective is to evaluate the efficacy of a series of minimal management options for composting manure and poultry litter on-farm to reduce concentrations of ten widely used pharmaceutically active compounds. Treatments are designed to span a range of practical management options – from the current practice of stockpiling the manure/litter to amending it with straw (to increase aeration) and adding insulating layers of straw. The second objective seeks to reduce the environmental footprint of composting by reducing methane, nitrous oxide, and ammonia emissions during composting. Greenhouse gas and ammonia emissions will be measured using replicate pilot-scale compost piles composed of manure/bedding from the BARC dairy and food/green wastes from local food processors. The first set of treatments will test the timing and frequency of compost mixing and turning. Subsequent experiments will measure and compare gas emissions from replicate piles constructed at initial bulk densities and from piles covered with 7-30 cm layers of finished compost. The third objective involves an evaluation of a relatively low-cost anaerobic digestion system that has significant potential for use on small farms. Six replicate pilot-scale plug-flow digesters, with two operational designs will be studied to provide long-term research on a system that has not been fully explored. Treatment efficiency, capital and operational costs, and gas utilization strategies will be evaluated for each type of system. Costs and benefits of different treatment strategies will be compared to existing manure management practices.

3. Progress Report
Although composting is an effective practice for stabilizing manure nutrients prior to land application, emissions of ammonia, methane, and nitrous oxide during composting are negative environmental consequences of this process. There is a need to determine the emissions of these gases during typical farm-scale composting operations and to test the effectiveness of different management measures to reduce emissions. Pilot-scale dairy manure composting studies were completed during the year using a photoacoustic gas analyzer for measuring ammonia, methane, carbon dioxide and nitrous oxide emissions. There is a global need to reduce dependency on fossil energy and to make use of sustainable energy feedstocks. Current anaerobic digestion technology in the U.S. is focused on large-scale dairy farms (greater than 500 cows). However, the vast majority of dairies (in the U.S. and elsewhere) have less than 200 cows. There is an urgent need to develop and support inexpensive anaerobic digestion systems for these small farms. One approach to increase biogas production at small dairies is to develop low cost digester systems. Nine pilot-scale low-cost digesters are under construction at the BARC dairy. Use of these digesters in concert with conventional digesters will allow direct comparison of biogas production under different loading rates and operating conditions.

4. Accomplishments
1. Greenhouse gas emissions from dairy manure composting operations. Manure management practices are widely regarded to significantly affect greenhouse gas (GHG) emissions from livestock operations. Unfortunately, there is relatively little specific information regarding the effect of different management practices on GHG emissions that is useful to producers. Manure composting is thought to reduce total GHG emissions relative to emissions from untreated manure. The objective of this study was to characterize emissions from pilot-scale dairy manure compost piles. Results from unmixed flat-top or conically shaped piles suggest that pile shape does not significantly influence GHG emissions. However, preliminary results suggest that pile composition may have a large effect on overall emissions. In the BARC dairy in Beltsville, Maryland, solids are screened out of the scraped manure slurry prior to anaerobic digestion of the manure liquids. The screened solids are composted along with manure and bedding from other parts of the dairy. Our preliminary results showed that emissions of methane (an undesirable greenhouse gas) increased with increasing amounts of dairy solids in the compost piles. Although screened dairy solids are typically present as a minor component in compost piles, additional studies are needed to determine the effect (if any) of low levels of screened dairy solids on methane emissions.

2. Over four billion pounds of chicken feather waste is generated by the U.S. poultry industry each year. Although feathers are typically disposed of in landfills, a new use for feather fiber is as a component of biopolymers. The primary advantage of feather-based biopolymers is that they reduce the use of petroleum-based feedstocks. However, an added benefit of some biopolymers is that they degrade relatively quickly under composting conditions. Since the fate of feather-based biopolymers during composting has not been studied previously, the aim of this study was to characterize the biodegradability of two biopolymers containing different amounts of poultry feather fiber. Our results showed that feather fiber was not degraded in either biopolymer after composting feather-fiber biopolymer fragments under standard conditions (60 days at 135 F). Raw feather fiber (primarily composed of the protein keratin) is itself quite resistant to microbial breakdown. However, results from other studies have shown that raw feather fiber can be degraded using special keratinase-producing fungi and bacteria. Additional studies are needed to see whether these organisms can speed the degradation of feather-fiber bioplastics.

3. Although algal cultivation and algae-based wastewater treatment systems have been in use for decades, there is renewed interest in such systems because of the potential use of the algal byproduct as a fertilizer or biofuel feedstock. Given the possible use of algal systems for treating varied sources of agricultural wastewater, robust and inexpensive methods of analysis for algal components are needed. At the present time, most algal samples are analyzed by conventional wet chemical methods, such as the Kjeldahl procedure for total nitrogen and phosphorus or by combustion techniques for total carbon or nitrogen. These procedures, while accurate, can be time consuming and expensive, and they generate chemical wastes. Infrared reflectance spectroscopy is an alternative method of analysis for determining the composition of a wide variety of materials ranging from forages and grains, food products, manure, and soil. Infrared spectroscopy can accurately and rapidly determine sample composition, while greatly reducing the waste associated with conventional analysis systems. The objective of this study was to investigate the feasibility of using near-infrared reflectance spectroscopy (NIRS) and mid-infrared reflectance spectroscopy (MIRS) to determine the composition of algal samples. Results showed that that both NIRS and MIRS can accurately determine ash and total nitrogen concentrations, but not phosphorus, sugar, lipid, or fatty acid concentrations in algal samples. Given these results, it may be possible to adapt and develop inexpensive infrared-based analyzers for determining ash and nitrogen concentrations in algal samples.

Review Publications
Ahn, H., Smith, M.C., Schmidt, W.F., Huda, M.S., Reeves III, J.B., Mulbry III, W.W. 2011. Biodegradability of injection molded bioplastics containing polylactic acid and poultry feather fiber. Bioresource Technology. 102:4930-4933.

Ahn, H., Mulbry III, W.W., White, J.W., Ingram, S.K. 2010. Pile mixing increases greenhouse gas emissions during composting of dairy manure. Bioresource Technology. 102:2904-2909.

Adey, W., Kangas, P., Mulbry Iii, W.W. 2011. Algal turf scrubbing: cleaning surface waters with solar energy while producing a biofuel. Bioscience. 61:434-441.

Last Modified: 06/26/2017
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