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Open Access | Published on October 5, 2025

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

Abstract

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.

Keywords
Orange Peel Waste, Anaerobic Digestion, Biochemical Methane Potential, Biochar, Granular Activated Carbon