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| Nitrogen Loss During Cleaning, Storage, Compost and Anaerobic Digestion of Animal Manures in Individual Treatment Unit |
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| KeyWord:animal manures; treatment unit; nitrogen loss |
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| Abstract: |
| Modern livestock production systems, based on intensification in large farms, produce huge amount of manures and slurries, which must be managed under appropriate disposal practices to avoid a negative impact on the environment. Compost is increasingly considered as a good way for manure treatment with economic and environmental profits, since this process eliminates or reduces the risk in terms of pathogen, parasite and weed seed spreading associated with direct land application of manure and leads to a final stabilized product. Recently, animal wastes have been successfully employed in anaerobic biogas production, which was viewed as a pragmatic approach to rationalize energy costs in animal farms. The digested slurries application as fertilizers is increasingly considered as a good way for recycling the surplus of manure for agriculture, and much research work has been carried out in the last decade. However, after manures clean from barns, nitrogen in manures would loss to varying degrees before farm application, Nitrogen losses impact negatively on the manure composting process, by decreasing nutrient concentration, reducing compost quality, and generating health and environmental problems. Nitrogen losses through composting can occur by NH3 volatilization, leaching and denitrification. In addition, nitrogen in manures could loss during the anaerobic digestion and the storage of digested slurries. The nitrogen content in manures cannot indicate the actual amount of nitrogen entered to farmlands. In order to understand nitrogen loss rate in manures and their actual application rate to farmlands, the first part of this paper reviewed the information on nitrogen loss in units of cleaning, storage, composting, anaerobic digestion of manures in the literature. Then, the latest research results from our group such as nitrogen losses from composting and anaerobic digestion of pig, dairy and poultry manures was presented. On the basis of literature review and our investigation, three treatment routes of manures and their nitrogen inputs to farmlands were proposed, i.e. via cleaning and storage（29%~80%N input with 55%N on average）, composting（6%~56%N input with 31%N on average）, and anaerobic digestion （9%~51%N input with 30%N on average）. Special attention should be paid to the nitrogen loss of manures in each treatment unit for providing scientific basis on the estimation of nitrogen load, allocation of planting area, evaluation of pollution risks and establishment of control criteria. |
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