Abstract
The aim of this study is to evaluate the material balance in a novel recycling process for production of poly-L-lactic acid (PLLA) from municipal food waste, and the possibility of recycling the byproduct as compost fertilizer. This process yielded approximately 7kg of PLLA from 100kg of food waste, which means that 33% of the total carbon in the food waste was recovered as PLLA. As a major byproduct, about 29% of the dry matter in the food waste was obtained as saccharified residue. This fraction showed a similar C/N ratio as food waste, while its electric conductivity and oil content were relatively low. Through successive high-temperature and aerobic treatment, the saccharified residue was converted into stable organic compost that could be used as a delayed-release nitrogen fertilizer for the growth of Komatsuna (Brassica rapa var. peruviridis). Moreover, in rice cultivation in paddy fields, the saccharified residue compost enhanced crop yield more effectively than chemical fertilizer. These results indicated the possibility of establishing a comprehensive system for recycling municipal food waste into PLLA plastic and nitrogen fertilizer.
