or use biomass
• One approach involves continuing to use fossil resources as raw materials, but systematically capturing CO
emissions and sequestering them underground using a process known as carbon capture and storage (CCS). The big advantage here is that today’s industrial production processes would not need to be changed. However, the storage sites must be suitable in terms of their geology, offering for example deep sedimentary layers that contain salt water. Such sites are not found all over the world.
• Another approach would see industry using carbon from CO
captured in advance from air or from industrial waste gases. This process is called carbon capture and utilisation (CCU). Hydrogen required for chemical products would be obtained from water using electricity. The approach would involve a major overhaul of chemical production processes and rebuilding large parts of the industrial infrastructure. In addition, it requires an extremely large amount of electricity – six to ten times more than CCS. “This method can be recommended only in countries with a carbon-neutral electricity mix,” Mazzotti explains, continuing: “We clearly demonstrate that using large quantities of electricity from coal or gas-fired power stations would, in fact, be much worse for the climate than the current production method based on fossil fuels.”
• A final option would be to use biomass (wood, sugar plants, oil plants) as raw material for the chemical industry. Although this method requires less electricity than the others, it involves very intensive land use to grow the crops – requiring 40–240 times more land than the other approaches.
The future of flying
Mazzotti and his co-authors based their study on the production of methanol, which is similar to the process used for producing fuels. Their work therefore also informs the discussion about future aircraft fuels, as Mazzotti points out: “We hear it time and again, even from experts, that the only way aviation can become carbon-neutral is through the use of synthetic fuels,” he says. “But that’s not true.” Producing synthetic fuels is an extremely energy-intensive process. If electricity from coal or gas-fired power stations were to be used for this purpose, synthetic fuels would have an even larger carbon footprint than fossil fuels. The study shows that there are at least two viable alternatives to synthetic fuels: aviation could continue to use fossil fuels if the CO
emitted by aircraft were captured and sequestered elsewhere, or the fuels could be obtained from biomass.
This research project was funded by the Swiss Competence Center for Energy Research – Efficiency of Industrial Processes (SCCER-EIP) and the Swiss Federal Office of Energy.