Dry Thermophilic Anaerobic Digestion Process of Swine Manure and Rice Straw: Towards a Sustainable Swine Manure Treatment System Based On Forage Rice Paddy

This study proposes a sustainable swine manure treatment system based on a forage rice paddy. Forage rice crops cultivated in a rice paddy are fed to livestock whereas the unused straws are provided to a dry thermophilic anaerobic digestion process as a substrate with swine manure to produce methane. Digested residues can be applied to a rice paddy as a fertilizer. In this study, effects of rice straws/swine manure (C/N) ratio and sludge retention time (SRT) on methane yields were investigated. Three bioreactors with C/N ratios of 8 (without rice straw addition), 20 and 30 were operated with decrease in SRT. The bioreactor with C/N ratio of 8 eventually lost methane production potential because of ammonia inhibition derived from swine manure. The highest methane yield of 110 Nm3/t-substrate was obtained at SRT of 30 day and C/N ratio of 20 and 30. Analysis on the system sustainability will be presented.