Driving with Synthetic Fuels
Synthetic fuels – so-called synfuels – can be produced using renewably generated hydrogen and CO2 from sources like biogas plants or from the atmosphere. In 2020, Empa launched a project to produce synthetic methane that can be used in gas-powered vehicles. The chemical reaction combining hydrogen and CO2 is carried out using a process developed at Empa.
Synfuels can be used in conventional gasoline, diesel or gas-powered vehicles. These fuels are climate-friendly since the CO2, which is released from the exhaust, is previously taken from the atmosphere for production. The CO2 is kept in a closed carbon cycle.
Synfuels and syngas can be mixed with gasoline, diesel or natural gas/biogas. The transition to renewable fuels can therefore take place smoothly and without further technological hurdles.
Losses during production
The disadvantage in producing Synfuels are the high energetic losses. Today, 50% of the primary energy is lost in the production of synfuels from renewable electricity. These losses can probably be reduced to 40 - 45% in the future. Economic considerations show that synfuels only have a market opportunity in areas where it is not possible to electrify means of transport - for example, long-distance trucks, cargo ships and aircraft.
Advantages in transportability and storage
However, looking at the energy system as a whole, synfuels have a key advantage: these energy carriers can be easily transported over long distances, therefore even distant renewable energy resources can be tapped. In addition, they can be stored over longer periods of time. They thus allow the necessary flexibilization of the local, renewable energy system.
Technology of methanation at move
The basic chemical process of methanation is known as "Sabatier process" for over 100 years: Methane (CH4) and water (H2O) are generated from carbon dioxide (CO2) and hydrogen (H2) by catalytic conversion. In conventional processes, there is one major problem: Due to the high temperatures, some of the produced water is converted back to hydrogen as a result of the water-gas shift reaction. The gas produced by the methanation reaction therefore contains a few percent of hydrogen. Therefore, it is not possible to feed it directly into the local gas grid. It is inevitable to separate the hydrogen in a subsequent chemical process.
At move, researchers circumvent this problem with a special process developed at Empa: the sorption-enhanced methanation process. The water, which is generated during the chemical process, is continuously adsorbed on a porous medium. This helps to eliminate the need for hydrogen separation after the process.
The CO2 for methanation as well as the water for the production of hydrogen will be extracted from the atmosphere directly on site from 2021 onwards using a CO2 collector made by the ETH spin-off Climeworks.