Bioconversion of wheat straw to energy via anaerobic co-digestion with cattle manure in batch-mode bioreactors (Experimental investigation and kinetic modeling)

Rising concerns about environmental issues including pollution control, waste management and energy demands have drawn the world's attention to the merits of renewable energy sources. In this regard, the anaerobic digestion of organic wastes for the purpose of bioenergy production is of particular importance. This study investigated the potential for biogas production from the co-digestion of a lignocellulosic biomass (wheat straw) with cattle manure after physical and chemical pretreatment at two Total Solids (TS) levels of 3% and 6% and three Inoculum-to-Substrate Ratios (ISRs) of 1, 2 and 4 (based on volatile solids). The materials were loaded into single-stage 1-liter digesters in batch mode under mesophilic conditions (35 ?) for 125 days. The best anaerobic digestion performance was observed in the treatment with 3%TS and ISR1, where the biogas and methane production yields were 0.510 and 0.307 m(3)/kg-VSadded, respectively. At both TS levels, biogas production increased with the increase in the Volatile Solids (VS) content of wheat straw and the decrease in ISR. This can be due to easier access of microorganisms to the organic matter and better microorganism-substrate balance, which ultimately result in improved digestion performance. The kinetic modeling results showed that the modified Gompertz model and the logistic function model had the highest level of consistency with the experimental results for TS3% and TS6%, respectively. The first-order kinetic model failed to provide a good estimate of biogas production from the co-digestion of wheat straw with cattle manure, irrespective of the TS level.

Automated summary

The study investigated the potential for biogas production from the co-digestion of lignocellulosic biomass (wheat straw) with cattle manure. The findings showed that the highest biogas production was achieved under specific conditions, and it was influenced by the volatile solids content of wheat straw and the inoculum-to-substrate ratio.