Compaction of bedded dairy manure storage to reduce ammonia and greenhouse gas emissions

Animal agriculture has been found to be a major contributor of aerial ammonia and greenhouse gases such as carbon dioxide, nitrous oxide, and methane particularly from manure handling and storage. Dairy cattle managed on bedded packs are becoming more common in Pennsylvania. A focus of this research was to reduce ammonia and greenhouse gas emissions from semi-solid dairy manure storage using compaction as the treatment method. Dairy manure with various bedding materials (woodchips, sawdust, or hay) was characterized in terms of moisture content and surface area in relation to mechanical strength and porosity. Sawdust and woodchips have a larger surface area than hay so use as a bedding additive can reduce the moisture content of manure and yield a higher mechanical strength when compacted. The results revealed that sawdust had a greater porosity even under compaction. This caused more carbon dioxide to be released and less methane because aerobic conditions were presumably maintained within the pile. Greater moisture content in the hay bedded material was conducive to anaerobic conditions with increased methane release. The effectiveness of moderate compaction as a treatment method to reduce ammonia and greenhouse gas emissions is still inconclusive; however, decreases in gas emissions were observed when bulk densities were increased to over 600 kg*m3.