Renewable energy from two-stage anaerobic digestion of organic wastes

Experimental studies of two-phase anaerobic digestion of corn steep liquor (a waste product from processing corn grain for starch extraction) were performed. For the first time, an automatic mode of operation was implemented in continuous processes with simultaneous production of hydrogen and methane using the developed computer system for monitoring and control of pilot bioreactors. The best results for daily biogas yield were obtained at an organic load of 20 g/L for hydrogen producing bioreactor, as the daily yield of biohydrogen is 0.74 dm³/L at a hydrogen concentration in biogas of 32.6% (0.24 dm³/L pure biohydrogen) and the daily biomethane yield in the methane producing bioreactor is 0.587 dm³/L at a methane concentration in biogas of 69% (0.4 dm³/L pure biomethane). The obtained energy is more than 40% compared to the traditional single-stage methane production process. A disadvantage is the need for additional purification from hydrogen sulfide of both gases before obtaining electricity and/or heat.