Food waste total recycling system – a novel zero effluent discharge process for converting food waste into three high market value products

ABSTRACT A novel three-step zero effluent discharge process was developed through a two-year research study. After completing the laboratory studies, a pilot system (50 kg/day) was built to prove the design concept. It comprised three steps: pretreatment, food waste decomposition and biogas production. Patented pretreatment was developed to treat wet and sticky Asian food waste. Through this machine, organic matter could be automatically separated from non-biodegradable matter and become fine slurry. Two bioreactors were used to cultivate two distinct types of microbial population. In the decomposition bioreactor, complex organics were broken down into three types of reusable products: floatable oil, a nutrient solution of simple organic acids and a protein-rich solid residue. The floatable oil could be sold as raw material for biodiesel, while the solid residue could be dried to produce eco fish feed. The nutrient solution was fed to the second bioreactor to produce biogas. The hydraulic retention time (HRT) of the two bioreactors were two to three days and seven to eight days, respectively. Wastewater coming out of the second bioreactor was recycled back to the pretreatment so that no wastewater was discharged. The developed process can be employed in decentralised systems to convert food waste into high market value products.