Temperature distribution and variation in passively aerated static compost piles

Abstract

Temperature distribution and variation in passively aerated static compost piles were investigated in three treatments with initial moisture contents of 73, 76 and 80%. Compost materials consisted of poultry manure slurry and peat or chopped straw. Three replicate piles were monitored simultaneously for each compost treatment. Two open-end perforated plastic pipes with 0·1 m diameter were used at the bottom of each pile for aeration purposes. Temperature in each compost pile was monitored using 23 or 33 thermocouples. Thermophilic temperatures above 45°C were attained in the piles within the first 2 days, confirming the effectiveness of passive aeration. Temperature distribution results indicate that air diffusion and convection were important passive aeration mechanisms. Cluster analysis of the temperature data suggest that ambient air was drawn into the compost through lower section of the piles, and warm air moved upwards inducing convection aeration. Temperature results were highly reproducible in the replicate compost piles of each treatment. The poultry manure slurry composting process took on average 30–85 days to complete depending on the amount of manure added and the initial moisture content of the three treatments.