Evaluation of methane production from liquid hot water pretreated Paspalum atratum and Brachiaria ruziziensis as alternative energy substrates

Atratum and ruzi grasses have illustrated high potential for methane production through anaerobic digestion. To enhance the utilization of these grasses for the production of renewable biogas, liquid hot water pretreatment was applied to break down various lignocellulose matter, in particular, hemicellulose. After pretreatment under optimal conditions (200 °C for 15 min), more than 90% of hemicellulose was removed and solubilized in the form of a clear hydrolysate. Xylose was the primary sugar in the hydrolysate, appearing in several forms, and acting as the major substrate for methane production. Total xylose yields for the atratum and ruzi grasses were 58 and 74 mg/g TS respectively. The pretreated atratum and ruzi substrates were evaluated for methane production resulting in an increased methane yield of at least 14%, and more than 70% biodegradability. This work demonstrates the potential for atratum and ruzi grasses to be used as a viable alternative to other energy crops such as Napier grass.