Comparison between Mesophilic and Thermophilic Methane Fermentation Treatments of Manure and Food Waste

Abstract

The Yagi Bioecology Center in Kyoto Prefecture treats cow and pig manure and food processing waste by mesophilic and thermophilic methane fermentation. Mesophilic and thermophilic digesters operate in parallel and the organic load of both digesters is about 2.0kg/m³/day. 1.5 years of operation data reveals that the removal rate of organic matter of the two digesters is almost the same. Both digesters produce almost the same biogas volume per unit of organic matter and the biogas content (CH₄, CO₂) is also the same. However, the thermophilic digester has a stronger disinfection effect for enterobacterium than the mesophilic digester. This data shows that digested liquid from the thermophilic digester is better for use as liquid fertilizer than that from the mesophilic digester.