Exergetic analysis in cane sugar production in combination with Life Cycle Assessment

The evaluation of the environmental sustainability of a technological option requires the consideration of the complete product life cycle. By using the methodology of a classical environmental Life Cycle Assessment (LCA), it is possible to analyze the environmental problems of the sugar industry through all stages of the full process including different options for the by-products valorization. Exergy and exergetic life cycle analysis are much more resource and product, and hence also efficiency, oriented. The Cumulative Exergy Consumption (CExC) has the advantage that different kinds of resources are quantified on one single scale, which is a unique feature in resource accounting. In this work, Exergetic Life Cycle Assessment was combined with a traditional LCA of cane sugar production process developed previously by Contreras et al. (Contreras et al., 2009), for assessing four different alternatives for by-products valorization of the cane sugar process. The CExC reports the exergy consumption of each stage of the process and the total consumption for each alternative which is important in resource consumption quantification, including renewability and hence process sustainability. Results show the advantage of combining both methods for the environmental assessment of cane sugar production. The application of this combination validates the results related with the category of resources and the contribution of the agricultural stage to the overall impact of the process. The environmental benefits of producing alcohol, biogas, animal food and fertilizers from the sugar production by-products were corroborated. The alternative IV has the lowest contribution to environmental impact in resource category and the minor value of the non-renewability index (6.59E-08).