Copyrolysis of food waste and rice husk to biochar to create a sustainable resource for soil amendment: A pilot-scale case study in Jinhua, China

Worldwide, massive amounts of food waste have been generated at increasingly accelerated rates, posing potentially great risks to the environment. Shifting traditional waste treatment to a sustainable bioeconomy thus challenges food chain management worldwide. In this study, food waste was copyrolyzed with rice husk to produce biochar with a pilot-scale industrialized system. The efficiency of the material conversion and the properties and functions of the produced biochars as well as the potential environmental impacts of pyrolysis were evaluated using in situ measurements, physico-chemical characterization and in vitro (pot) experiments with biochar. The results showed that the emissions of potential toxic compounds and metals from the pyrolysis system were within the guideline limits under the legislation of China or the EU commission. On average, biochar yielded approximately 20% of feedstock and contained a total organic carbon content of 433 g kg(-1). In the pot experiment, Chinese cabbage yield and quality were significantly improved, and the plant uptake of heavy metals was significantly reduced in soil amended with food waste biochar compared to no biochar amendment. Furthermore, the food waste biochar was blended with mineral nutrients to create a biochar based compounded N-P-K fertilizer. Application of the biochar based compound fertilizer exerted a significant positive effect on cabbage growth and nutrient use efficiency relative to a conventional mineral compound fertilizer. For per tonne of dry mass of food waste, copyrolysis costed less than 60 USD but gained a gross profit of more than 30 USD. Therefore, the copyrolysis of food waste with crop residues could be applicable to the safe recycling of food waste into value added products to raise agricultural production.