Assessment of methane production through co-digestion of biomass from the sugarcane and livestock sectors

Abstract

Biogas is a bioenergetic mixture of gases obtained through anaerobic digestion (AD) of complex organic matter. This organic matter may be present in urban, industrial, and agricultural residues. The integration of these resources into co-digestion systems can increase methane productivity by optimizing the nutrient balance for AD. Therefore, identifying potential substrates for AD is crucial for optimizing and managing this process. This study aimed to use cattle manure (CM) and blood water (BW) as potential co-substrates for co-digestion with sugarcane vinasse (V) by assessing the biochemical methane potential (BMP) of mono- and co-digestion systems. Kinetic adjustment was conducted to understand the dynamics of the system, and the energy potential was estimated based on the lower heating value of methane. The BMP of V mono-digestion reached 49.67 NmLCH₄ g⁻¹VS, whereas that of CM reached 119.93 NmLCH₄ g⁻¹VS. For co-digestion systems, the mixture V-67 + BW-33 (67% of the mixture are composed of V and 33% of the mixture are composed of BW; volume by volume—v/v) reached the highest BMP of 369.47 NmLCH₄ g⁻¹VS, representing an increase of 87%, in relation to the V mono-digestion. For the tests with the three substrates, the best condition in terms of methane production was in the proportion V-16.5 + CM-67 + BW-16.5 (245.13 NmLCH₄ g⁻¹VS), resulting in an increase of 80% and 51% in comparison to the mono-digestion of V and CM, respectively. In kinetic modeling, the Gompertz model fits the experimental data well. These results highlight the potential of the sugarcane industry integration with livestock farming.