The implementation of the circular economy and green energy transition for the treatment of agricultural waste into bioenergy

presents greater challenges in mountainous and rural areas. The integration of rural-farming plant (tomato plant residue,

TR; and cacao pod husk, CPH) and animal-based biomass waste (deer manure, M) with an anaerobic digestion (AD) plant

as a substrate has the potential to produce biohydrogen and biomethane as a source of bioenergy in rural farming areas.

This study aims to investigate the potential of these feedstocks, including mono- and co-digestion of M and TR in singlestage

AD. The co-digestion of M and TR signifi cantly enhanced the biogas and methane production performances, with an

increase of 27.5–173.2% compared to mono-digestion. The ratio of M to TR aff ects the total solid (TS) load in the initial

AD process. A TS greater than 3% was found to be more favorable for methane production. This co-digestion method avoids

the accumulation of volatile fatty acids (VFAs) in the mixture which prevents inhibition of methane production. The eff ect

of initial substrate and inoculum concentration in two-stage AD using dried CPH powder was also explored in this study.

The acidic thermochemical pretreatment of CPH has been demonstrated to signifi cantly enhance biohydrogen production.

The optimal biohydrogen and methane production using CPH in two-stage anaerobic digestion was achieved by a substrate

concentration of 12 g Volatile Solid added /L and an inoculum concentration of 10% v/v (volume/volume). According to this

study, all residue generated by the agricultural sector has the potential to be utilized with greater added value within the

agricultural industry to support the green energy transition in rural farming areas.