Development of a process for enhanced biogas production from lignocellulosic feedstocks using an efficient thermophilic inoculum and its metagenomic study

Abstract

Biogas production through anaerobic digestion is the easiest route to utilize organic waste. However, some of the organic wastes are not easy to digest and hence, there is a requirement of harsh pretreatments. Although pretreatment accounts high costing, it is required for efficient digestion of such waste due to its recalcitrant and complex nature. Therefore, there is a need to develop a process where no pretreatment would be required. This paper presents an effort to develop an efficient inoculum to produce enhanced biogas production using untreated feedstocks. A thermophilic inoculum was developed using water hyacinth as a feedstock and soil samples as a source of microbes collected from different deep insides of cattle manure dumping yards from the local area of Muzaffar Nagar, Uttar Pradesh. The process temperature was optimized and found to be 52 °C. The developed inoculum was further tested at 52 °C on different feedstocks including paddy straw, Napier grass, corn stover, corn cob, banana pseudostem, mustard stalk, etc. Surprisingly, most of these feedstocks showed efficient anaerobic digestion and produced enhanced biogas in a short hydraulic retention time. Metagenomic study of inoculum showed the presence of thermophilic bacteria and archaea which are reported in the literature for hydrogenic, acidogenic, acetogenic, methanogenic (acetoclast/hydrogenotrophs) steps of the anaerobic digestion process. Novelty of this study lies in the in-house developed thermophilic inoculum, which has a unique broad range spectrum to degrade different types of agricultural feedstocks in a short period of time without any pretreatment and makes the process economically viable.