Techno-economic and environmental impact assessment of an olive tree pruning waste multiproduct biorefinery

Abstract

This work focuses on the economic performance and environmental assessment of two biorefinery schemes using 100 t/day of olive tree pruning waste as feedstock. The first scheme is based on a multiproduct biorefinery producing 6363.64 m3/yr of ethanol, 999.31 t/yr of xylitol, and 1221.51 t/yr of antioxidant, obtaining a positive investment balance with a net present value (NPV) of 11.56 M€ in a 20-year period with an initial investment of 39.5 M€ (antioxidants account for 60.2% of revenues). In addition, it shows lower environmental impacts: 0.435 kg CO2 eq in global warning, 0.007 kg 1,4-DCB in human carcinogenic toxicity, 0.148 kg oileq in fossil resource scarcity for 1 kg OTP consumed, in comparison to the business-as-usual production of ethanol, xylitol and antioxidants (7.96 kg CO2 eq, 0.444 kg 1,4-DCB and 2.228 kg oileq). The second scheme considered is the standalone production of antioxidants, showing a similar economic performance (NPV = 11.9 M€) to the previous multiproduct biorefinery with lower initial investment requirements (24.9 M€). This process configuration also reduces some important environmental impacts such as global warming impact (0.55 kg CO2 eq) and freshwater consumption (0.067 m3), with respect to the multiproduct scheme. Thus, it has been demonstrated that antioxidants production from OTP is a promising alternative in terms of both process economics and environmental performance.