Environmental Assessment of Bio-based Feedstocks For Renewable Chemicals

Abstract

Bio-based feedstocks are increasingly used as alternatives to their fossil-based counterparts in industry. While these feedstocks are often considered more environmentally friendly, they may also cause severe environmental impacts. Therefore, their performance should be critically assessed. This thesis investigates the environmental impacts of bio-based feedstocks, namely vegetable oils (palm oil, sunflower oil, rapeseed oil, soybean oil), fish oil, starches from wheat, maize, potato, and cassava, cane sugar, beet sugar, and wood derivatives such as pulp, tall oil, and lignin. Available Life Cycle Assessment (LCA) studies and LCA data from databases such as Agri-footprint and ecoinvent were used to identify hotspots and dominant contributors, mainly across key impact categories of climate change, eutrophication, ecotoxicity, land use, and water consumption. The ReCiPe and Environmental Footprint life cycle impact assessment methods revealed that the highest normalized and weighted scores for all feedstocks correspond to freshwater ecotoxicity, marine ecotoxicity, and climate change. The main source of ecotoxicity was identified as the use of agricultural chemicals. Land use change emissions, fertilizers, and energy consumption were identified as major hotspots for climate change in crop-based feedstocks. Diesel consumption, natural gas used in the pulping process, and CO2 production were identified as the hotspots for fish oil, the pulping process, and lignin isolation units, respectively. To complement the LCA analysis, Energy Return on Investment (EROI) and carbon efficiency parameters were calculated. All the investigated feedstocks demonstrated a net energy gain, with EROI values of greater than one, and the highest EROI values were assigned to palm oil and fish oil. Carbon efficiency values highlighted fish oil and starches as the feedstocks with higher carbon efficiencies. In addition, a quantitative comparison of the environmental impacts of feedstocks was carried out based on the normalized values among the available regions in the Agri-footprint and ecoinvent databases across different impact categories. Fish oil showed the lowest impacts, while vegetable oils, especially sunflower oil, exhibited the highest environmental burdens. Finally, based on the hotspot analysis, EROI, carbon efficiency, and the quantitative environmental impact comparison of feedstocks, fish oil could be considered the best-performing feedstock, while vegetable oils had the most impact on the environment. Starches, wood derivatives, and sugars demonstrated intermediate performance.