Butyric Acid Fermentation during Ensiling of Wilted Maize Stover for Efficient Methane Production

The performance of conventional processes for ensiling crop residues for biogas production is usually enhanced with lactic acid fermentation to reduce organic matter (OM) loss. In this study, butyric acid fermentation in the ensiling process of wilted maize stover (WMS) with glucose was directly and indirectly enhanced with Clostridium tyrobutyricum (Glu-CT) and CaCO3 (Glu-CaCO3), respectively. The effect of butyric acid fermentation and lactic acid fermentation during ensiling on the subsequent biogas production was investigated. Butyric acid fermentation was successfully enhanced in the Glu-CaCO3 treatment but not in the Glu-CT treatment. Analysis of storage performance and microbial activity revealed that enhanced butyric acid fermentation triggered synergetic acid hydrolysis and enzymolysis during ensiling and increased the biodegradability of the WMS. The specific methane yield (methane yield(measured)) and methane yield(orig) (corrected with storage loss) of the 60 d of ensiled WMS in the Glu-CaCO3 treatment increased by 20.1% and 10.4%, respectively, compared to the values on day 0, which were significantly higher than that of WMS subjected to lactic acid treatment (P < 0.05). The trade-off between OM loss and increased methane yield was positive when the butyric acid fermentation was enhanced during ensiling. Hence, the criteria for conventional ensiling of WMS for biogas production could be reconsidered.