Life Cycle Assessment of acetone production from captured carbon dioxide Using bio-fermentation at the PYROCO2-pilot plant

Abstract

Due to its need of carbon feedstocks, the chemical industry is expected to become the major driver of oil consumption in the future, with its greenhouse gas emissions increasing annually. The PYROCO2-project aims to reduce the industry’s dependency on fossil resources, moving it in a direction of increased sustainability. At the time of writing, the PYROCO2-project is still in early development where the design process for a pilot plant, eventually to be constructed south of Oslo, Norway, is underway. The project aims to produce acetone via two fermentation processes, using captured carbon dioxide and hydrogen gas, produced through electrolysis, powered by renewable electricity. The aim of this thesis is to investigate how the future pilot-plant will perform regarding environmental impacts by applying life cycle assessment. This was further analysed using sensitivity scenarios, to verify the hotspots for environmental impacts within the production system. This provides providing important knowledge for the planned future construction of similar plants at other locations. The environmental impact hotspots, identified for the pilot plant were the capture, purification and liquefaction of carbon dioxide, and the electrolysis, which performance is highly dependent on the electricity mix used. This was confirmed by the sensitivity analysis, using German electricity, as opposed to Norwegian. In terms of climate change, the PYROCO2-pilot plant outperforms conventional acetone production considerably, potentially acting as a negative emissions technology. The impacts on toxicity was shown to be higher for the PYROCO2-pilot plant. However, these are connected to metal use for the expansion of the electricity grid, where previous life cycle assessments have shown that embodied emissions for electricity transmission and distribution are negligible.