Digestate quality and biogas enhancement with laterite mineral and biochar: Performance and mechanism in anaerobic digestion

Low biodegradation poses significant challenges to widespread adaptation of anaerobic digestion (AD) technology mainly attributed to low biogas yield. The biodegradation of organic substrate can be increased by enhancing direct interspecies electron transfer (DIET) by adding laterite mineral and biochar to the AD system. This study evaluates the efficiency of Laterite-mineral (LM), biochar (BC) and combination of LM and BC (LM-BC) to enhance biogas yield. Varying concentrations of LM (0.1–0.3 %), BC (0.2–0.6 g/L), and LM-BC (0.05 % + 0.1 g/L₋ 0.15 % + 0.3 g/L) were introduced in AD systems of cow-manure (CM) at mesophilic conditions (37 °C). Results showed that BC 0.6 g/L and LM0.3 % produced the highest biogas (417 mLg−1 VS and 409 mLg−1 VS, respectively), followed by LM0.1 % - BC0.05 g/L (367 mLg−1 VS). The BC0.6 g/L and LM0.3 % also showed a higher chemical oxygen demand (COD) removal rate (41 % and 40.2 %, respectively) than the control group (30.1 %) and LM0.1 % - BC0.05 g/L (37.1 %). Moreover, digestate with BC0.6 g/L and LM0.3 % (5.73 and 5.65 %, respectively) had higher fertility than LM0.1 % -BC0.05 g/L (5.39 %) and control check CK (4.56 %). Hence, BC0.6 g/L and LM0.3 % are comparable to enhance the efficiency of AD system via DIET and are recommended for integration into large-scale AD systems.