Techno-economic and ex-ante environmental assessment of C6 sugars production from spruce and corn. Comparison of organosolv and wet milling technologies

Abstract

This study assesses the techno-economic and environmental performance of C6 sugars production from softwood (spruce) and corn. Two technologies were considered in the assessment: organosolv of spruce woodchips (2nd generation) and corn wet milling (1st generation). Process models were developed to generate relevant data to assess the technical performance and derive inputs for the economic and environmental assessments. The economic assessment was carried out using Net Present Value (NPV) as indicator, while the environmental assessment followed a prospective cradle-to-gate life cycle assessment (LCA) for 5 impact categories. The results indicate that when organosolv is integrated with an anaerobic digestion unit, the net energy requirements are lower than those of the wet milling process to produce an equivalent flowrate of C6 sugars. Assuming equivalent C6 sugar prices for the two technologies (300 €/t), the corn based technology shows positive NPV (178 M€) and lowest fixed capital investment requirements (55 M€). The organosolv technology (coupled to anaerobic digestion) also shows positive NPV (238 M€) at base case lignin prices (630 €/t), but higher fixed capital investment needs (236 M€). The economics of the organosolv process were found to be highly sensitive to sugar and lignin yields and prices as well as biomass feedstock costs. From an environmental perspective, the organosolv based routes show relatively better performance than corn wet milling, with 3 categories including climate change and non-renewable energy use showing lower impacts and 2 showing potentially higher impacts. Overall, the organosolv process (2nd generation) shows better performance from an environmental point of view in addition to a positive NPV. However, the inherent risks of new technologies and high investments associated with the 2nd generation technologies assessed in this work, mean that significant additional development, coupled with appropriate government support, are likely necessary before full-scale implementation.