Optimization of Biogas Production from Co-digestion of Whey and Cow Manure

Anaerobic co-digestion is effective and environmentally attractive technology for energy recovery from organic waste. Organic, agricultural and industrial wastes are good substrates for anaerobic co-digestion because they contain high levels of easily biodegradable materials. In this paper enhancement of biogas production from co-digestion of whey and cow manure was investigated in a series of batch experiments. The influence of whey ratio on specific biogas production in a mixture with cow manure was analyzed at 35 and 55 degrees C, for different initial pH values and for different concentrations of supplemental bicarbonate in experiments carried out over 12 days. Good biogas production (6.6 dm(3)/dm(3)), methane content (79.4%) in a biogas mixture and removal efficiencies for total solids (16%) were achieved at optimum process conditions (temperature of 55 degrees C, 10% v/v of whey and 5 g/dm(3) NaHCO3 in the initial mixture). In order to validate optimized conditions for co-digestion of whey and cow manure in the one-stage batch process, the experiments were performed within 45 days. The high biogas production (21.8 dm(3)/dm(3)), a good methane content (78.7%) in a biogas mixture as well as maximum removal efficiencies for total solids (32.3%), and chemical oxygen demand (56.3%), respectively indicate that whey could be efficiently degraded to biogas in a one-stage batch process when co-digested with cow manure.