Effect of Chemical Pretreatment on Characteristics and Biogas Production of Corn Cob through Mono and Co-digestion

Abstract

Anaerobic digestion (AD) process has the capability to sustainably meet the growing global energy needs and thus energy crisis. It helps in converting a variety of biomass into bioenergy and digestate. Agricultural waste especially corn cob (CC) is a very suitable option for AD process. However, the recalcitrant structure of corn cob and high carbon to nitrogen ratio (C/N) makes it less susceptible to AD. Therefore, the focus of the

study was to perform alkaline pretreatment of the CC and to perform its mono and co- digestion with food waste (FW) i.e. cooked rice as co-substrate to optimize the C/N for

effective AD. The corn cob was subjected to pretreatment with varying NaOH concentrations of 1%, 1.5%, 2%, 2.5% and 3%. The raw and pretreated corn cob was subjected to AD i.e. both batch mode mono and co-digestion in mesophilic condition for 40 d. The ultimate analysis of food waste was done which assured its nutrient richness thus making it a good option to be used as a co-substrate with CC. The results revealed that maximum cellulose recovery was obtained in 1.5% and 1% NaOH pretreated samples showing cellulose recovery of 128% and 101.4% respectively. While the lignin removal for 1.5% NaOH pretreated CC was 63.38% and for 1% NaOH pretreated CC, it was 68.75%. The cumulative biogas yield of 1%, 1.5% and 2% increased by 64.76%, 24.36% and 10.32%, respectively in comparison to control group. In short, lower dosages of NaOH i.e. 1%, 1.5%, 2% were more effective than the higher dosages of 2.5% and 3% which showed decline in biogas yield due to excessive delignification. Furthermore, the more biogas production was indicated in co-digestion as compared to the mono-digestion process. The order of cumulative biogas produced in anaerobic co-digestion (ACD) of CC with FW is: 1% >1.5%>2.5%>2%> 3%. The research concluded that alkaline pretreatment was successful in increasing cellulose recovery and reducing lignin content, and that co-digestion of pretreated lignocellulosic substrate with other organic waste generated more biogas than its mono-digestion.