Slurry covers to reduce ammonia emission and odour nuisance

Covering of liquid manure storage facilities causes additional costs. Furth ermore, the building of rigid covers such as tent roofs over large slurry l agoons is prohibitively expensive. Therefore, emission reducing effects and floating behaviour of low-cost covers were investigated. Such alternative cover materials are granules, chopped straw and rape oil. Tests took place both in the laboratory and in the field. On-farm studies s erved to determine emissions from liquid manure surfaces in large slurry st orage facilities. Laboratory tests were carried out in transparent Perspex containers on a 651 scale. The floating behaviour of the covers and the sed imentation of slurry during storage and after homogenization were observed. The ammonia emission was also measured here and sampling for odour measure ments and chemical analysis was carried out. Cover materials showed very different behaviour. The granules made a closed cover within a few hours after homogenization, while rape oil rose to the surface only during a period of several days. Chopped straw made a solid fl oating layer infiltrated with slurry. Laboratory scale and on-farm studies with granules and straw as covers redu ced odour emission by about 83-91%. Ammonia emission decreased by about 80- 91%. The emission reduction of 85% for a 6 mm rape oil layer was similar to the other covers, but the 3 mm oil layer showed an insufficient effect. (C ) 1999 Silsoe Research Institute.