Impact of Organic Load on Methane Yields and Kinetics during Anaerobic Digestion of Sugarcane Bagasse: Optimal Feed-to-Inoculum Ratio and Total Solids of Reactor Working Volume

Abstract

The effect of increasing organic load on the specific methane yields (SMYs) and kinetics of methane production during the anaerobic digestion (AD) of sugarcane bagasse (SB) was investigated in batch experiments at 37 °C. The organic load of the batch AD system was increased based on an increase in the feed-to-inoculum (F/I) ratio (T1–T5) and increase in the Total Solids (TS)% of the working volume (T6–T10). The results show that in both the treatment sets, an increase in organic load led to a decrease in SMY. Higher organic loads in terms of F/I ratio (T4 and T5) were inhibited due to Volatile Fatty Acid (VFA) accumulation. On the other hand, higher organic loads (T8, T9 and T10) in terms of the higher TS% of the working volume was inhibited by the accumulation of NH4-N. Thus, an organic load of 50 gVS/L at an F/I ratio = 1.0 and TS = 10% (T3) was found to be the highest organic load that had no significant inhibitions among the tested treatments. The results from the kinetic studies show that the first-order kinetic model is the best fit for the SMY data, with average differences% of 2.32% and 3.13% for treatments T1–T5 and T6–T10, respectively.

Keywords

• F/I ratio
• critical organic load
• VFA accumulation
• free water availability
• kinetic modelling
• specific methane yields