Techno-economic analysis of a food waste valorisation process for lactic acid, lactide and poly(lactic acid) production

A sustainable food waste valorisation process was proposed by designing a plant with a capacity of 10 metric tons (MT) hour⁻¹ of food waste powder with a 20-year lifetime. Three scenarios were proposed with different products: Scenario I) lactic acid, Scenario II) lactide, Scenario, and III) poly(lactic acid) (PLA). Mass balance showed conversion yields of 3.1 MT of 80% lactic acid, 1.7 MT of lactide, and 1.3 MT of poly(lactic acid) from 10 MT of food waste powder. All scenarios were economically feasible, but Scenario I had the highest annual net profits (US$ 22,184,169), internal rate of return (31.1%), net present value (US$234,803,060) and the shortest payback period (5.1 years) at a discount rate of 5%. The minimum selling prices of lactic acid, lactide and poly(lactic acid) were US$943 MT⁻¹, US$2073 MT⁻¹ and US$3330 MT⁻¹, respectively. Sensitivity analysis showed that the prices of lactic acid, lactide and poly(lactic acid) were the largest determinants of the profitability in the plant while the sale of by-products (animal feed) was also critical to the plant's economics. This work has cast insights on the techno-economic performance of a sustainable food waste treatment under a decentralised approach in urban areas.