Anaerobic mono-and co-digestion of fruit and vegetable residues: Effects on biogas yield and biofertilizer¹

Mono e codigestão anaeróbia de resíduos de frutas e vegetais: Efeitos no rendimento de biogás e no biofertilizante

ABSTRACT

The proper disposal of fruit and vegetable waste is essential to promote environmental sustainability, reduce the carbon footprint, improve soil quality, and contribute to the transition to a circular economy. This study examined the impact of incorporating dairy cattle wastewater (DCWW) into anaerobic co-digestion with fruit and vegetable residues and utilization of the resulting biofertilizer as a diluent in the anaerobic mono-digestion of fruit and vegetable residues (recycle). The specific biogas and methane production and the agronomic quality of the biofertilizer were evaluated in a semi-continuous trial. Two startup strategies were employed: initially, the reactors were entirely fed with inoculum (biofertilizer derived from DCWW), and fruit and vegetable residue feedstock was gradually introduced. Anaerobic co-digestion of fruit and vegetable residues with DCWW yielded the highest specific production of biogas and methane at 720 and 436 L kg^-1 of volatile solids (VS), respectively. The addition of DCWW increases fruit and vegetable residue alkalinity by 249% and reduces the volatile acidity by 83.4%. Anaerobic mono-digestion of fruit and vegetable residues enhances macronutrient recovery in the biofertilizer through recycle. Logistically, directing fruit and vegetable residues to rural areas for anaerobic co-digestion with DCWW promotes agricultural biofertilizer use.

Key words:
specific biogas and methane production; process stability; nutrient recovery; recycle

HIGHLIGHTS:

Anaerobic mono-digestion of fruit and vegetable residues is viable using biofertilizer as a diluent.

Anaerobic co-digestion of fruit and vegetable residues and dairy cattle wastewater improves biogas and methane yields.

Anaerobic co-digestion of fruit and vegetable residues and dairy cattle wastewater improves biofertilizer quality.