Most farm problems with animal wastes occur in modern intensive livestock enterprises where manure is handled as a slurry. It is not practical to treat slurry in the same way as domestic sewage: it should be used on land as a source of plant nutrients. On most farms, this can be done only at certain times of the year and so slurry has to be stored. Storage gives rise to problems of mixing, handling, application, pollution, smell and pathogen survival which can often be solved by separating slurry with special machinery into solid and liquid fractions. Where odour is a serious problem, however, some form of limited aeration will usually provide the best solution. For intensive pig units on limited land close to houses, the NIAE has evolved a new system of slurry treatment which can convert all the slurry from a fattening piggery into inoffensive solids. When incorporated into a piggery for 500 pigs being planned by the Ministry of Agriculture, Fisheries and Food, the system should also reduce smell substantially both inside and outside the building.