Greenhouse Gas Release From Stored Dairy-Cattle Manure Slurry

Emission of methane (CH4) and carbon dioxide (CO2) from 8 to 9% dry matter content dairy cattle manure slurry, stored in a below-grade 296 m3 covered concrete storage tank (7.2 x 14.7 x 2.8 m deep) was determined during winter ('93-'94) and summer ('94) seasons. Mean daily temperature of ambient air at the site ranged from -28º to 15ºC and 6º to 30ºC during the winter and summer determinations, respectively. Slurry temperature varied with depth, the warmest manure being near the bottom during the winter (4 - 10ºC) and near the surface during the summer (14º - 23ºC). Biogas was collected in floating-cover gas collectors under which the slurry was either confined in a pipe or unconfined. Daily biogas production was variable and was lower in winter than in summer. Production from confined manure was about twice that from unconfined manure. Cumulative biogas production amounted to 1.3 and 0.6 liter per liter of stored manure during 118 days of summer storage. Methane content of the biogas ranged from 27 to 34%. Results of this study suggest that greenhouse gas release from stored dairy cattle manure slurry would be low under cool climatic conditions similar to those of eastern Ontario.