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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

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: 10/19/2017
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