Anaerobic Digestion System Incorporating Intermediate Thermal Treatment: A Laboratory Scale Investigation into Enhancing Methane Productivity

Abstract

Anaerobic digestion with intermediate thermal hydrolysis (AD+ITH) is a new configuration currently under investigation due to the evolution of the pre-treatment TH technology. This project used batch and semi-continuous laboratory scale anaerobic digestion tests to investigate the possibility for enhanced methane productivity and volatile solids destruction. A semi continuous AD+ITH reactor was operated for 210 days, thermal treating sludge at 165°C for 30 minutes. The AD+ITH produced more methane and volatile solids reduction than conventional anaerobic digestion by 1.5 times. However, an energy balance estimated that the inclusion of a TH unit without thickening would not result in a self-sustaining process and have a negative energy balance. Further investigations are required at pilot-scale, and to determine whether the cost of extra methane is decreased through the added complexity of this AD+ITH.