Co-digestion of wheat straw and animal manure pretreated with calcium hydroxide for biomethane production: Kinetic study

Abstract

Bio-methane produced from lignocellulosic biomasses has potential to be an alternative sustainable resource of energy. Among the various types of biomasses, lignocellulosic biomass has sufficient amount of carbohydrates (celluloses, hemicelluloses and lignin), thus, significant probability to convert into biogas. The recalcitrant structure of lignin causes hindrance in the biogas production which can be resolved by chemical pretreatment of biomass before anaerobic digestion. The present investigation is an attempt to assess the influence of chemical pretreatment of lignocellulosic biomass for biogas production in batch experimental studies. Lignocellulosic biomass (wheat straw) was pretreated by different concentrations of calcium hydroxide Ca(OH)2 (1%,2%,4%,10% and 15%) at ambient temperature i.e. 30 °C to improve its biodegradability in anaerobic digestion process. It was found that pretreatment of wheat straw with 10% Ca(OH)2 resulted maximum biogas production i.e. 565.63 ​ml, while pretreatment with 15% Ca(OH)2 resulted relatively lower yield of biogas production i.e. 464.92 ​ml. Gompertz model was applied on experimental data of biogas production and revealed that the maximum rate of biogas production (μmmld-1) was found with 10% Ca(OH)2 pretreatment, while lowest rate of biogas production was found with untreated wheat straw. Overall, present study concludes that selection of optimum concentration of Ca(OH)2 efficiently improves the rate of biogas production from wheat straw.