Improving biogas yields using an innovativ e concept for conversion of the fiber fraction of manure

The potential of a new concept to enable economically feasible operation of manure-based biogas plants was investigated at laboratory scale. Wet explosion (WEx) was applied to the residual manure fibers separated after the anaerobic digestion process for enhancing the biogas yield before reintroducing the fiber fraction into the biogas reactor. The increase in methane yield of the digested manure fibers was investigated by applying the WEx treatment under five different process conditions. The WEx treatment at 180 °C and a treatment time of 10 min without addition of oxygen was found to be optimal, resulting in 136% increase in methane yield compared with the untreated digested manure fibers in batch experiments. In a continuous mesophilic reactor process the addition of WEx-treated digested fibers in co-digestion with filtered manure did not show any signs of process inhibition, and the overall methane yield was on average 75% higher than in a control reactor with addition of non-treated digested fibers.