How important synthetic fuels, also known as e-fuels, will be in a future energy system is a question many are hotly debating these days. The answer, of course, depends on whom you ask and whom they represent. To bring some facts to the table, energy institute ifeu recently conducted a study for German environment agency UBA to determine the amounts of carbon dioxide and other pollutants emitted by fuels produced through power-to-X.

Titled “Comparing clean energy carriers,” the study was written jointly by ifeu staff and researchers working at the German Aerospace Center – DLR and the Joanneum Research Forschungsgesellschaft. The authors found that many pathways for producing synthetic fuels release between 85 percent and 90 percent fewer emissions than those relying on fossil energy sources.

Even when using lower heating values as a basis, hydrogen continues to have the lowest environmental impact, followed by synfuels, Fischer-Tropsch fuels and methanol. Additionally, biomass production pathways are, on average, more sustainable than pathways sourcing electricity. Overall, ifeu said that while e-fuels can contribute to climate protection, there is likewise a risk that they could lower air, water or soil quality.

“E-fuels are not the answer. They should only be used as a bridging technology.”

Werner Diwald, DWV chairman

“E-fuels are one option to give automakers a bit more time to adapt.”

Christoph Bender, chief executive of oil association MWV

E-fuels are produced from clean energy and can be used in conventional ICEs. Their manufacture (aka synthesis) requires carbon dioxide, which will later be emitted during combustion. In contrast to fossil fuels, e-fuels do not emit additional carbon dioxide but bind it temporarily. They are said to extend the useful life of gasoline and diesel engines without offering advantages similar to those of electric motors running on clean electricity.