Co-digestion of orange peels and marine seaweed with cattle manure to suppress inhibition from toxicants

Traditionally, anaerobic digestion (AD) is applied for the simultaneous generation of energy and treatment of various organic wastes. For example, despite orange peels (OP) and seaweed (SW) are highly available for AD, their physicochemical composition can inhibit the microbiome and collapse the process. In the present work, we examined the combination of OP and SW with livestock manure (MN) at a co-digestion process. At first, batch toxicity tests revealed that D-limonene and gallic acid at 0.2% v/v and 2.28 g L⁻¹ respectively solely inhibit methane generation. At batch assays and based on added volatile solids (VS), the mono-digestion of OP and SW had methane yields of 398.4 ± 9.4 and 348.6 ± 10.2 m³ t_VS⁻¹, respectively. Furthermore, continuous mode experiments were conducted in order to examined process performance and bioenergy outcome at the co-digestion of OP, SW, and MN at various organic loading rates and substrate contributions. This work revealed two successful operation strategies when OP and SW were co-digested with manure resulting in methane yields of 264.5 ± 5.2 and 220.5 ± 5.2 m³ t_VS⁻¹, respectively. The results of this work potentially could be applied when dealing with other types of algal biomass.