The concept captures the CO2 within the exhaust system, converts it into a liquid and stores it on the vehicle. The liquid CO2 would then be delivered to a service station where it could be turned back into fuel using renewable energy.
The project is being coordinated by the Industrial Process and Energy Systems Engineering group, led by François Maréchal, at EPFL’s School of Engineering.
The scientists propose to combine several technologies developed at EFL to capture CO2 and convert it from a gas to a liquid in a process that recovers most of the energy available onboard, such as the heat from the engine.
First, the vehicle’s flue gases in the exhaust pipe are cooled down and the water is separated from the gases. CO2 is isolated from the other gases with a temperature swing adsorption system, using metal-organic frameworks adsorbent, which are specially designed to absorb CO2.
The materials are being developed by the Energypolis team at EPFL Valais Wallis, led by Wendy Queen. Once the material is saturated with CO2, it is heated so that pure CO2 can be extracted from it.
High speed turbocompressors developed by Jürg Schiffmann’s laboratory at EPFL’s Neuchâtel campus use heat from the vehicle’s engine to compress the extracted CO2 and turn it into a liquid.
That liquid is stored in a tank and can then be converted back into conventional fuel at the service stations using renewable electricity.
The researchers’ calculations highlight that a truck using one kilogram of conventional fuel could produce three kilograms of liquid CO2, and that the conversion does not involve any energy penalty.
Only 10% of the CO2 emissions cannot be recycled, and the researchers propose to offset that using biomass. The system could theoretically work with all trucks, buses and boats, with any type of fuel.