Techno-economic and Life-Cycle Assessment of One-Step Production of 1,3-Butadiene from Bioethanol Using Reaction Data under Industrial Operating Conditions

Abstract

A process to produce 1,3-butadiene (1,3-BD) from ethanol in a one-step reaction with a Hf-Zn catalyst was designed using experimental data from the catalyst performance under industrial conditions, taking into account the presence of water and other byproducts in recycled ethanol. The techno-economic and life cycle assessments of the process were performed and compared to the naphtha-cracking route. In these assessments two scenarios were defined to evaluate the impact of catalyst selectivity to 1,3-BD (58 and 69%). For the assessment of the environmental sustainability, three further cases were defined to determine the influence of the geographical location of the production plant considering the world's major ethanol suppliers: The United States, Brazil, and Europe. The results of the economic evaluation show that for a plant with a production capacity of 200 ktonne/year of 1,3-BD, and considering an average market price of azeotropic ethanol (450 €/m3), the minimum butadiene selling price for a 10% rate of return on investment ranges 1.13-1.26 times the average butadiene market price (1529 €/tonne). The process can be profitable for favorable combinations of market prices of ethanol and 1,3-butadiene, but the profitability of the process ultimately relies on the development of higher selective catalysts to reduce the consumption of ethanol per tonne of 1,3-butadiene since ethanol dominates the production costs. The LCA shows that switching from naphtha-derived butadiene to biobutadiene can lead to substantial reductions in CO2 emissions (GWP100) (8-26%) but, in turn, to a significant increase in water consumption (62 to 137-fold) and cumulative energy demand (50-250%). Being that ethanol is the major contributor to all impact categories (65-98% of the impacts), the location of the plant and catalyst selectivity significantly affects the environmental sustainability of the process. Considering the three impact categories and the uncertainty analysis of the LCA results, the best plant location would be Brazil, with a negative median impact value for GWP100 (-73 to -52 kg CO2 eq/tonne 1,3-BD) and the lowest median value for water consumption (235-299 m3/tonne 1,3-BD) but the highest median value for cumulative energy demand (207-241 GJeq/tonne 1,3-BD), the latter due to the low ethanol yield of sugar cane. Copyright © 2020 American Chemical Society.