Potential methane production of spent sawdust used in the cultivation of Gymnopilus pampeanus

Abstract

Gymnopilus pampeanus (GP) is a mushroom consumed in Argentina. Spent Populus sawdust (SPS) obtained from the cultivation of GP was used to test methane production. The effect of two substrate/inoculums (S/I) ratios was analysed. Three treatments were carried out, T1: 80% SPS + 20% I, T2: 40% SPS + 60% I and T3: 40% PS (Populus sawdust) + 60% I. After 105 days the cumulative biogas production resulted in 201.2 and 147.8 mL/g VS for T2 and T1 respectively. Methane production increased 62.2% when S/I decreased 83.3% (112.9 and 71.7 mL/g VS for T1 and T2 respectively) while for treatments which used the same percentage of inoculums (60%) the fungal action on the sawdust improved methane production in 970%. Regarding the kinetics of methane production, Gompertz equation demonstrated a good performance of the adjustment of experimental data (R2 > 0.98) and the values of the kinetic parameters indicated that SPS structure showed better accessibility than PS to the methanogenic system. The long time of adaptation (32.2 days) and the low methane production rate (1.7 mL/g VS d) observed in SPS, revealed that the methane production is still not enough for energy purposes.