Towards Sustainable Shipping: Climate change and other environmental perspectives on carbon-based marine electrofuels and onboard carbon capture

The global, local, and regional environment is under pressure from human activity. Shipping is a human activity causing emissions to air, water, and soil, which has direct and indirect effects on the environment. New fuels and propulsion technologies are required to lower the emissions from the shipping sector and reduce the impact on the environment. Fuels produced through electricity, water, and carbon dioxide, so-called carbon-based electrofuels, are one group of fuels suggested to reduce the environmental impact of shipping. Another proposed solution is onboard carbon capture. The aim of this thesis is to promote further discussion on how to assess future marine fuels and propulsion technologies by establishing the environmental impacts of these emerging technologies.A mixed methods approach to environmental assessment is used, combining thematic analysis, literature reviews, and life cycle assessment. Through case study applications, the environmental performance of electromethanol, electromethane, and onboard carbon capture are investigated when applied in the maritime sector in northern Europe. Thematic analysis is used to investigate what is hindering low-emission fuels from being further utilized in maritime cargo transportation. The results show that if renewable energy is used in fuel production and CO2 is captured from a source not acting as a driver of fossil fuel extraction, climate change impact can be reduced by using carbon-based electrofuels instead of fossil fuel options. Potential trade-offs were identified as carbon-based electrofuels can lead to higher pressure on human health impacts than today’s conventional fuels. The extent of the trade-offs is uncertain and affected by limitations in the methodological approach. Suggestions on how to address these uncertainties are introduced and analyzed. Assessment of future scenarios for large-scale marine electromethane production in Sweden reveals that combined biofuel and electrofuel production likely results in the lowest environmental impacts. Onboard carbon capture can lower the climate change impact if combined with electrofuel production or carbon capture and storage. The environmental impacts at large depend on the bunkered fuel and the choice of carbon capture technology. The results underscore the importance of integrating life cycle assessment with other scientific methodologies. The environmental impacts of capital goods should be included in life cycle assessments of future marine fuels, and scenario-based assessments are preferable over single-vessel evaluations