Dry digestion of crop wastes: Studies on dry anaerobic digestion with agricultural wastes

This paper reports the requirements for batch dry-fermentation with agricultural wastes. The optimum initial solids content is 25–30%, with ratios of rice straw to manure (on a dry matter basis) of 2 or 1:1. The inoculum should be over 30% by volume. In the course of the fermentation, when biogas production rate is falling, two additions of inoculum and fresh pig manure lengthen the duration of a biogas production rate of above 0·3 m3 m−3 day−1, o enhance the total biogas volume and to promote the degradation and utilization of the raw material. This process of dry-fermentation with agricultural wastes gives relatively high total biogas yield, biogas production rate, and degradation rate of raw materials and needs a simple routine management. NH4HCO3 can substitute for manure to mix with straw, as well as the nitrogen source, to give similar results.