Competitive use of sugarcane for food, fuel, and biochemical through the environmental and economic factors

Abstract

Bioethanol demands for transport face uncertainty; additionally, the emergence of electric vehicles is raising concerns among the ethanol producers towards the future demand and viability of the industry. Thus, there is a need to look for new pathways of sugar and ethanol utilization. However, the environmental and economic implications of the existing and proposed systems must be assessed to ensure sustainability. The study aims to evaluate and compare the environmental and economic performances of sugarcane for three new sugar-electricity-polylactic acid (PLA) systems with the existing sugar-electricity-ethanol system. The environmental hotspots of the existing and proposed sugarcane biorefinery systems are investigated and potential measures for enhancing environmental sustainability of the new systems identified. Life cycle assessment (LCA) is used for evaluating the environmental sustainability assessment of the sugarcane biorefinery and the eco-efficiency indicator, combining both the economic and environmental performances. The ReCiPe method with the hierarchist perspective at midpoint and the endpoint levels is used for quantifying the environmental impact scores. The reference unit is a tonne of cane processed at the biorefinery. The eco-efficiency is calculated based on the ReCiPe endpoint single score (“Pt”) and the values in “US$” of products from the different biorefinery systems. The results reveal that the PLA pathways to substitute ethanol and sugar production (PLA scenarios 1–3) can generate product values of about 83–220 US$/t cane processed leading to increased eco-efficiency values for all three PLA scenarios as compared to the existing sugar-electricity-ethanol system. The highest eco-efficiency (22 US$/Pt) is obtained for the pathways of PLA (scenario 3) and sugar-PLA (scenario 2). However, the LCA results show increased environmental impacts for all three PLA biorefinery scenarios. This implies that the new PLA pathways do not lead to “strong” eco-efficiency improvement, i.e., the improvement is not in both environmental and economic dimensions. Recommendations are provided to improve the environmental performances of both the existing and the new PLA biorefinery systems. The sugarcane-based PLA biorefinery could be an option for the case that the existing sugar-electricity-ethanol faces an uncertainty on ethanol demand. Nevertheless, there is a trade-off between the increased environmental impacts and the higher price. Strong eco-efficiency improvement must be encouraged to the sugarcane-based PLA biorefinery systems. Using high-pressure boilers at the mills and changing cultivation practices to avoid the cane trash burning are recommended for the better decoupling of the environmental and economic performance of the sugarcane biorefinery systems.