Transient Shifts in Hydraulic Retention Times Improve the Methane Production from Ruminal Hydrolysates of Agave Bagasse

BACKGROUND Valorization of lignocellulosic wastes such as agave bagasse from tequila industries can be enhanced using efficient biomass pretreatments. However, the next challenge requires finding the best process conditions to produce methane and remove chemical oxygen demand (COD) from the pretreatment hydrolysates. In this work, an innovative feeding strategy based on alternating hydraulic retention times (HRT) was investigated to improve methane production from ruminal hydrolysates of Agave tequilana bagasse. RESULTS The ruminal hydrolysate provided a substrate rich in volatile fatty acids (VFA) for direct use in the methanogenic process. The alternating feeding strategy increased the volumetric methane production rate by up to 25% (from 0.76 +/- 0.05 to 0.95 +/- 0.03 L CH4 L-1 d(-1)) compared to operating at a constant feeding rate, equivalent HRT of 15 h, and organic loading rate (OLR) of 8 g COD L-1 d(-1). The alternating HRT operation improved VFA conversion without modifying the methane yield, and the COD removal was increased by 14%. The system stability, measured through the alkalinity index, was maintained during the proposed feeding strategy and after the increase in OLR. CONCLUSION The proposed feeding strategy is a promising tool for improving methane production from agave bagasse hydrolysates. The strategy was robust and easy to apply, which could expand its use for a wider variety of substrates. (c) 2021 Society of Chemical Industry (SCI).