Innovative organic waste pretreatment approach for efficient anaerobic bioconversion: Effect of recirculation ratio at pre-processing in vortex layer apparatus on biogas production

Abstract

Agricultural waste, called biomass, is of great interest as a renewable energy source. The purpose of this work was to determine the optimal recirculation rate (RR) values of the solid digestate when applying a new approach to the intensification of anaerobic conversion, providing a high quality biogas yield. This approach includes solid digestate recirculation and pre-processing a mixture of raw waste and solid digestate in a vortex layer apparatus. For this, the operation of an experimental biogas plant without recirculation and with recirculation was considered, starting from very low RR values, from 0.034 to 1, to ensure a high methane production rate (MPR) and methane yield (MY). From the point of view of MPR and MY, the recirculation ratios of 0.034 and 0.071 look the most attractive, however, with a recirculation ratio of 0.5, the content of hydrogen sulfide de-creased to 14 ppm with a simultaneous increase in MPR by 12 % compared to the control.