Covering of liquid manure storage facilities causes additional costs. Furthermore, the building of rigid covers such as tent roofs over large slurry lagoons is prohibitively expensive. Therefore, emission reducing e!ects and #oating 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 "eld. On-farm studies served to determine emissions from liquid manure surfaces in large slurry storage facilities. Laboratory tests were carried out in transparent Perspex containers on a 65 l scale. The #oating behaviour of the covers and the sedimentation of slurry during storage and after homogenization were observed. The ammonia emission was also measured here and sampling for odour measurements and chemical analysis was carried out.
Cover materials showed very di!erent 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 #oating layer in"ltrated with slurry.
Laboratory scale and on-farm studies with granules and straw as covers reduced 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 insu$cient e!ect.