A study was set up to investigate the environmental effects of anaerobic digestion and separa-tion of slurry. Volatilisation of odour and ammonia from treated and untreated slurry were compared both during storage and following land application. It was found that ammonia volatilisation was higher from uncovered stores of anaerobically digested and separated slurry than from untreated slurry, however, when slurry stores were covered efficiently, the loss rate was low and equal for treated and untreated slurry. Ammonia volatilisation following land application was found to be lower from both anaerobically digested and separated slurry compared to untreated slurry. Treatment of slurry by anaerobic digestion and separation did not reduce odour nuisances during storage, however, odour nuisance from slurry stores was found to be efficiently reduced by an artificial crust cover of the slurry stores. During land application the odour nuisances were found to be lower for anaerobically digested and separated slurry than for untreated slurry