Effect of Lactate and Starter Inoculum on Biogas Production from Fresh Maize and Maize Silage

Abstract

Lactate is a key intermediate during anaerobic digestion of carbohydrates; however, it fails to receive significant consideration in biogas plants. We examined the influence of lactic acid on biogas production. Two commonly used feeds, fresh maize and maize silage, were selected as substrates due to their difference in lactic acid contents. Additionally, inocula from an agriculture-based biogas plant, a waste water treatment plant and a standardised laboratory reactor were selected to investigate the impact of starter culture on the process. Experiments demonstrated increased total biogas yield of up to 45% in the lactate-rich maize silage over the lactate-devoid fresh maize, but only in cases where the starting inocula had been previously exposed to lactic acid. Our findings suggest lactic acid is a significant intermediate in biogas production and merits consideration. Additionally, the ability of the starter inoculum to utilize lactic acid is an important factor in process optimization and enhanced biogas production.