Life cycle assessment and multi-criteria analysis of sugarcane biorefinery scenarios: Finding a sustainable solution for the South African sugar industry

Abstract

Abstract The valorisation of sugarcane lignocelluloses is a potential solution to ensure the sustainability of the South African sugar industry. The sustainability of six biorefinery scenarios were assessed and compared. The scenarios are: a CHP coal supplemented itaconic acid biorefinery (Scenario 1), bioenergy self-sufficient (ESS) itaconic acid biorefinery (Scenario 2), ESS polyhydroxybutyrate (PHB) biorefinery (Scenario 3), ESS succinic acid and PHB biorefinery (Scenario 4), ESS succinic acid biorefinery (Scenario 5) and a stand-alone CHP plant (Scenario 6). An environmental life cycle assessment (eLCA) was conducted to identify potential problem or ‘hot spot’ areas in the respective processes, and to compare the environmental impacts of the bio-products to one another, as well as to their fossil reference products. Carbon footprint and water scarcity impact were included as the two eLCA parameters, together with four life cycle costing (LCC) parameters and one social life assessment (sLCA) parameter, in a life cycle sustainability assessment (LCSA). The LCSA parameters were normalized and weighed in a multi-criteria decision analysis tool to determine the most sustainable solution for implementation by the South African sugar industry. It was found that a trade-off exists between the environmental and techno-economic performance. Scenario 4 is the most sustainable scenario due to the environmental advantage obtained by the high succinic acid production volume, since the environmental burden is shared across a large number of bioproduct units together with the economic advantage of a high PHB selling price, while being bioenergy self-sufficient.