Effect of temperature on hydrolysis rates of selected biowaste components

The rates of hydrolysis and biodegradability of six selected components of biowaste were determined as a function of temperature under mesophilic anaerobic conditions. The first-order hydrolysis rate constants ranged from 0.03–0.15 d−1 at 20°C to 0.24–0.47 d−1 at 40°C. The biodegradability of the biowaste components ranged from 5% to 90% but did not depend on temperature. The increase in hydrolysis rate at increasing biodegradability suggests that the rate of hydrolysis of particulate organic matter is determined by the adsorption of hydrolytic enzymes to the biodegradable surface sites. This concept is supported by the Arrhenius-type behavior of hydrolysis rate and the calculated activation energy of 64 ± 14 kJ mol−1. Comparison of the hydrolysis rates of this study with data on the performances of batch, dry biowaste digesters showed that the digesters were not running optimally. It is proposed that the reduction in conversion efficiencies is related to VFA inhibition of the hydrolysis due to limited transport of VFA in the biowaste bed.