Life cycle assessment of novel CCS technologies

Abstract

CO2 emissions from the combustion of fossil fuels are the largest sources of anthropogenic greenhouse gas emissions to the atmosphere. Carbon capture and storage (CCS) is one of the better options to mitigate these emissions and thereby limit global warming even while continuing the use of fossil fuels for power generation. As CCS increases the energy consumption of the power plant itself, there will be an increased use of fuel and therefore also increased environmental impacts connected to this. To calculate these impacts it is important to include the entire supply chain and life cycle of the power plant.This thesis involves a tiered hybrid life cycle assessment of natural gas- and coal power plants with chilled ammonia process (CAP) and sorption enhanced water-gas shift (SEWGS) capture technologies. These novel capture technologies are two of the least studied when it comes to environmental assessments. The results from this assessment are compared to two of the more studied capture technologies, post-combustion capture by monoethanolamine (MEA) and oxyfuel combustion capture.Both the CAP capture alternative and the SEWGS alternative have been shown to decrease the global warming potential (GWP) in a natural gas plant by 70%. For the coal-fired power plants, the CAP technology managed a decrease in GWP of 77% while the SEWGS technology showed a decrease of 77.5%. This decrease comes at a cost of other impact categories where for example the freshwater ecotoxicity potential (FETP) has an increase of 87-88% for both the CAP and SEWGS capture technologies in NGCC plants. This impact category has an increase of 25 and 22% for the CAP and SEWGS technologies in the coal-fired power plants.Compared to post-combustion capture by MEA and oxyfuel combustion capture, the results were clear on MEA being the least preferable option in an environmental perspective for both coal- and natural gas-fired power plants. Oxyfuel combustion capture, on the other hand, was shown to be the most preferable option.