Pig production is responsible for 65 per cent of all odour complaints and 10 per cent of water pollution incidents. In addition, the disposal of pig slurry effluent may create major difficulties in nitrate sensitive areas either from run off or leaching of liquids. In situ composting of pig manure has the potential to eliminate these problems whilst encouraging pig producers to use welfare positive, bedded systems. In situ composting is a system of housing in which pigs are contained on a deep bed of sawdust. The bed is actively managed by aeration and the use of commercial additives to encourage composting of excreta as it is produced. The system appears to give an odour and liquid free environment. Such systems cannot be encouraged however until it is clearly established that there are no environmental or health disadvantages.