Pilot-scale operation experience of anaerobic Co-digestion for possible full scale implementation

Abstract

Anaerobic co-digestion of sewage sludge with four beverage wastes (namely beer, soft drink, fruit juice, and wine) was evaluated using a dedicated pilot research plant. Temporal variation in the sludge's organic content highlighted the importance of using a mono-digestion control reactor for a systematic comparison with co-digestion. Results indicate that chemical oxygen demand (COD) is a better parameter compared to volatile solids (VS) for determining the organic loading rate during co-digestion with beverage waste that contain solubilised organic carbon. In this study, all beverage wastes investigated here (with the exception of wine) were suitable for co-digestion. H2S content in biogas decreased during co-digestion, possibly due to the dilution effect by the additional biogas generated from sulphur-lean organic rich waste. Results from this study show that the organic content in most beverage waste can be readily and completely converted to biogas. At 10% substrate addition (v/v) beer, soft drink and juice addition did not observably affect total COD and VS in the digestate, whilst increasing biomethane production relative to the control by 39, 41 and 64% respectively. Furthermore, the interchanging of co-substrates did not result in any observable impact on digestion performance. Further investigation is recommended to ascertain the low performance of wine waste co-digestion with sewage sludge.