Towards sustainable aviation: Environmental life cycle assessment of co-electrolysis-based syngas production

Kurzfassung

According to the International Energy Agency (IEA), the aviation sector is responsible for about 2.5% of global energy-related carbon dioxide emissions. This has led to increased efforts to reduce the environmental impact of the aviation industry. One promising solution is Sustainable aviation fuel, which relies on syngas, a mixture of carbon monoxide and hydrogen. Typically, syngas is produced through coal gasification or steam methane reforming, but both methods generate significant carbon emissions. Solid oxide co-electrolysis presents a cleaner way to produce syngas with much lower emissions. However, the extent of these reductions depends on several factors, such as the energy source, system operation, and component degradation. For this reason, a detailed life cycle assessment is necessary to compare co-electrolysis with conventional methods and to identify the factors that contribute most to environmental impact. This study adopts a cradle-to-gate approach that includes carbon dioxide captured directly from the air using a direct air capture unit. The electricity requirement for the co-electrolysis operation is modelled to include consumption during standby periods as well as additional demand resulting from stack degradation over time. Heat demand is estimated using Aspen Plus software, which also incorporates heat recovery from exhaust gases. Two electricity supply scenarios are considered: the German electricity mix for 2024 and a fully renewable electricity supply. The life cycle inventory accounts for the materials used, the energy required for manufacturing, and the replacement of solid oxide cells throughout the lifespan of the system. The results indicate that electricity supply is the largest contributor to climate-related emissions. When powered by renewable electricity, the co-electrolysis process can achieve net-negative emissions, outperforming traditional methods. However, there are trade-offs, as impacts such as resource use and land occupation increase due to the need for larger infrastructure. Additionally, the source and supply of heat play a significant role in the overall environmental footprint. These findings highlight the importance of having clean energy sources to make syngas production more sustainable.