Microbial Pretreatment for Biogas: Analyzing Dairy Rumen Anaerobic Bacteria Inoculum’s Impact on Alfalfa Biomass and Energy Value

Abstract

Lignocellulose is a complex and abundant biomass source, and finding ways to efficiently break it down is essential for various applications, including bioenergy production and waste management. Biogas production can be significantly enhanced by adding rumen fluid to the anaerobic digestion process, which contains a variety of microorganisms with the enzyme activity necessary to breakdown complex lignocellulosic materials. This study examined the influence of rumen anaerobic bacteria inoculum on alfalfa biomass biogas yield and quality. Inoculation experiments were performed, and the higher biogas yield from organic matter was gained in experiment (A), with a rumen fluid addition of 340 ± 3.2 L/kgVS, compared to the utilization of a digestate alone in (B), 238 ± 1.2 L/kgVS. The results demonstrated that a pretreatment temperature of 37 °C (experiment D) yielded the highest biogas production, 381 ± 3.9 L/kgVS, and maintained a high methane content of 63.9 ± 1.9%. Notably, pretreatment at 25 °C resulted in only a 3% increase over the raw sample and a pretreatment at 50 °C (respectively, experiments C and E) showed no significant changes, emphasizing the sensitivity of pretreatment efficiency to temperature variations.