Synergistic effect of sugarcane scum as an accelerant co-substrate on anaerobic co-digestion with agricultural crop residues from non-centrifugal cane sugar agribusiness sector

Abstract

Anaerobic co-digestion (AcoD) of the main residues from the non-centrifugal cane sugar (NCS) making process, agricultural crop residues (ACR) and sugarcane scum (SCS), was evaluated using biochemical methane potential tests. Substrates were pretreated: ACR through particle size reduction, and SCS with dilution. The maximum methane yield of 0.276 Nm³ CH₄ kg^-1 VS_added occurred at an ACR of 2 mm and at 12.5% dilution of SCS, at a ratio of 75:25 based on volatile solids, which was 30.2% and 5.9% higher compared to SCS and ACR in mono-digestion, respectively. ACR was a substrate of adequate buffer capacity for the AcoD stability, while the SCS, in addition to helping accelerate the process, also helped improve the inoculum's methanogenic and hydrolytic activity. The first-order kinetic and dual-pool two-step models were suitable to describe methane yield. AcoD of ACR with SCS is a good option for the treatment of streams in the NCS agribusiness sector.

Keywords: Accelerant co-substrate; Agricultural crop residues; Anaerobic co-digestion; Sugarcane scum; Synergistic effect.