Raw manure is loaded into a trough (3) contained within an enclosure which is sealed against the ingress of fresh air. The atmosphere within the enclosure is circulated using fan (19) through the manure and is applied to the manure until this reaches a temperature of not less than 125 DEG F. The manure is then allowed to rest until it reaches naturally a temperature of at least 150 DEG F and it is maintained at that temperature until completion of pasteurisation. It is then force-cooled by driving fresh air through the resultant compost and held until commencement of a first phase of conditioning bacterial activity. Natural heating of the compost occurs during the first conditioning phase and the atmosphere within the enclosure is recirculated through the compost throughout that phase with fresh air added in a manner such as to limit the maximum temperature reached by the compost during this phase. Exhaust gases from the enclosure are monitored to detect a time at which those gases become substantially free from ammonia, so indicating completion of the first conditioning phase. In a subsequent second conditioning phase the atmosphere is recirculated through the compost and at least 5% by volume of fresh air added substantially continually to the recirculating atmosphere to cool the compost to below 110 DEG F and so complete conditioning. Mushrooms may be cultivated on the conditioned compost thus prepared. IMAGE
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