Assess a new strategy and develop a new mixer to improve anaerobic microbial activities and clean biogas production

In the present study, the optimization of digestion conditions including the best mixture of substrates (cow manure, municipal waste, and kitchen waste) and pretreatment (adding NaOH and H2O2) was studied to increase the CH4 production using a combined D-optimal design. The optimum digestion conditions named new strategy showed that with the amounts of 42, 56, and 2% of cow manure, municipal waste, and kitchen waste and 3.98 and 0.02% of NaOH and H2O2, respectively, the CH4 production reached to the most amount. The new strategy were then provided for semi-industrial biogas plant mixed with Pneu-mechanical and mechanical mixers. The biogas compounds and microbial communities of the biogas slurry were compared among the researched treatments. The results showed that the Pneu-mechanical mixer under un-optimum and optimum conditions could respectively, increase CH4 about 20.65 and 18.75%, reduce H2S more than 21% and 312%, and decrease O-2 about 28 and 141%, but it increased CO a little. On the other hand, the new strategy increased the CH4 production up to 123%, decreased H2S up to 300% and CO up to 28% with increasing the anaerobic microbial communities more than 3000%. It was concluded that by using the Pneu-mechanical mixer in optimum conditions, CH4 could be enriched very well even with a less anaerobic microbial community. (C) 2018 Elsevier Ltd. All rights reserved.