Sustainable valorization of agricultural waste into bioplastic and its end-of-life recyclability for biochar production: Economic profitability and life cycle assessment

Abstract

While the industrial sectors have recently focused on producing bioplastic materials, the utilization of edible feedstocks and the generation of wastes and byproducts during the bioplastic synthesis process might delay achieving the environmental sustainability strategy. To overcome these limitations related to bioplastic industrialization, this study focuses on synthesizing bioplastics from waste sources, followed by recycling its end-of-life (e.g., spent and exhausted) material into biochar. Sweet potato peel waste, banana pseudo-stems, and cooking oil waste were used to extract starch, cellulose, and glycerol (a plasticizer) involved in bioplastic manufacturing, respectively. It was found that the cellulose content of 30% w w⁻¹ in bioplastic maintained the best physicochemical, mechanical, and biodegradability properties, recommending a high applicability for food packaging. The exhausted bioplastic was then pyrolyzed to maintain a biochar yield of 32.60 ± 0.89%, avoiding the risk of secondary pollution from waste material disposal. This biochar was utilized to treat wastewater generated from the bioplastic synthesis process, showing the optimum adsorption factors of biochar dosage = 3.81 g L⁻¹, time = 102 min, and solution pH = 7.81. The combined bioplastic production, waste pyrolysis, and wastewater treatment scheme could earn profits from biomaterial sales, carbon credit, and pollution reduction shadow price, maintaining a 6.78-year payback period and a 12.09% internal rate of return. This integrated framework depicted better contributions to the mid-point/end-point life cycle assessment impact categories than the only bioplastic production scenario. This study contributed towards achieving several sustainable development goals (SDGs), including SDG#3: human health protection, SDG#6: wastewater treatment, and SDG#12: waste recycling.