A in-vessel composter with forced aeration and mechanical turning was set up and evaluated at Ridgetown College, University of Guelph. During the first week, manure is added to a substrate (corn cobs, barley straw, wood chips, tree leaves, or any combination of the preceding) until a desirable mositure ocndition of 55% – 70% is achieved. The ratio, by weight of liquid manure to substrate was 2.4:1 to 6.9:1 for straw, and was lower fir wood fibre and corn cobs. Odour dterminationwas made on a subjective basis, using staff that worked in the building. The composting system and the method in which liquid manure was added to the system contributed to an environment where there was seldom any evidence of liquid manure odours.