Impact of Carbon-Based Materials on the Anaerobic Digestion of Citrus Processing By-product

Orange peel waste holds promise for biomethane production via anaerobic digestion, though challenges such as the presence of d-Limonene, an inhibitory compound, and seasonal availability persist. In this study, ensiled OPW was used in Biochemical Methane Potential (BMP) tests to evaluate its degradability and assess the effect of carbon-based additives (i.e. granular activated carbon and biochar). Methane production was monitored over time and modelled using first-order and modified Gompertz kinetics. The highest methane yield (578 ± 59 NmL CH₄/gVS) was observed in the control, consistent with literature values for ensiled OPW. Yields from tests where additives were used ranged from 520 to 560 NmL CH₄/gVS, with no significant enhancement. However, kinetic modelling indicated a slight increase in the maximum methane production rate (Rₘ) using an additive, suggesting an acceleration in methane production kinetics.