Enhancing anaerobic degradation of corn stover residues and biogas production via rumen microorganisms

Abstract

Corn is one of the most common cultivations in Greece and worldwide. Raw materials like corn stover contain a remarkable amount of organic content, which could be transformed anaerobically into biogas, using as an alternative energy source. The development of efficient methods to overcome the limitations arisen from the nature of lignocellulosic biomass is a challenge since pretreatment is required to break down its complex structure. An economically-feasible biological approach to disrupt the structure of lignocellulosic materials, like corn stover, is through the valorization of hydrolytic potential of microbial communities present in rumen. Rumen microbiota has demonstrated the ability to break down lignocellulosic biomass. Thus, this work aims to enhance biogas production from corn stover residues using rumen fluid microbiota. The anaerobic digestibility of corn stover in BMP (Biochemical Methane Potential) tests and CSTR (continuous stirring tank reactors) was examined using rumen fluid as inoculum, in presence of control. Three organic loading rates (OLR), i.e. 1, 2, and 3 g VS/L.d, were tested, to define the optimum OLR for corn stover digestion. Moreover, experiments to define the optimum corn stover to rumen fluid ratio to optimize biogas production were carried out. Addition of rumen inoculum into the anaerobic digester at daily basis was found to be essential to enhance biogas production from corn stover. The optimum corn stover residues concentration in rumen fluid for optimum biogas production was 4% w/v. Addition of rumen fluid microbiota in the CSTR operating under various OLRs enhanced biogas production by 2–6.3 times.