The fossil fuel era is ending. Countries such as Switzerland and the EU member states, which aim for climate neutrality by 2050, must stop burning oil, natural gas and coal by then at the latest, because the associated CO2 emissions are not compatible with that goal. So-called synthetic fuels could replace them, at least in part.
Synthetic fuels are produced from hydrogen and CO2 and can usually directly replace petrol, diesel, kerosene and natural gas. If the hydrogen is produced using electrolysis and electricity from renewable sources and the CO2 comes from the air, their production and combustion represents a CO2-neutral cycle. Problem solved?
Unfortunately, it's not quite that simple. The production of these synthetic fuels requires a lot of electricity and is currently very expensive. In addition, there are still open questions on the technical side, and to date very few plants produce such synthetic fuels in large quantities.
E-fuel research projects at LEA
This is where researchers at the Laboratory for Energy Systems Analysis come in. As part of several projects, they want to find out how climate- and environmentally sustainable synthetic fuels really are, to what extent their costs can be reduced, where they can be produced in the most environmentally sustainable and cheapest way, for which purposes they are most urgently needed, and what role they will play in achieving Switzerland's climate targets.
Christian Bauer, a long-standing scientist in the Laboratory for Energy System Analysis, has an overview of all these projects. "Recently, there has been a lot of hype surrounding these synthetic fuels, which are often referred to as ‘e-fuels.’ Some see them as the solution to sustainable heating, flying and driving. Others demonize them. I see it as our role to demonstrate the environmental and economic consequences associated with the widespread use of e-fuels, and to explain for which purposes they make sense, and for which they do not. Ultimately, our work should help to set the right course towards a climate-neutral Switzerland at an early stage, without relying on false promises," says Bauer.
Although the individual research projects are all concerned with synthetic fuels, they each have a very specific focus.
SHELTERED
In the SHELTERED project, Zipeng Liu, Romain Sacchi, Christian Bauer, Kannan Ramachandran and Martin Densing are working to find out what role low-carbon fuels will play in achieving Switzerland's net-zero target.
Zipeng Liu explains: "The special thing about this project is that, for the first time, we are looking at the full range of low-carbon fuel options for reducing greenhouse gas emissions in Switzerland, including synthetic fuels, the direct use of electricity from renewable sources, and biofuels." To this end, the environmental burdens of individual fuels will be assessed using life cycle assessment, along with their global production and supply chain costs.
"Both the global perspective and the view into the future are very important," says Martin Densing. "This is the only way we can determine the best locations for the production of synthetic fuels. In terms of costs and greenhouse gas emissions, it makes a huge difference whether e-fuels are produced in Morocco, for example, with plenty of wind and sun and then imported, or here in Switzerland, where we are blessed with neither a lot of wind nor sun."
The life cycle assessments and cost calculations are linked to a Swiss and a global energy system model. This allows the optimal combination of technologies and fuels to be determined to achieve the net-zero target by 2050, taking into account various framework conditions, such as the development of oil, gas and CO2 prices or PV systems and CO2 capture from the air.
The final results of the project, which is funded by the Swiss Federal Office of Energy, are expected at the beginning of 2025.
SynFuel Initiative
The SynFuel Initiative focuses on air traffic and so-called "sustainable aviation fuels" (SAF for short). There are two types of SAF: one based on biomass waste, the other on a combination of hydrogen and CO2. Great hopes have been pinned on the latter to make air travel more climate-friendly because, unlike biomass waste, it could one day be available in sufficiently large quantities. The topic is also gaining momentum thanks to the regulation that recently came into force at EU level, which stipulates a 70% share of SAF in aviation fuel by 2050.
Romain Sacchi, Dimitri Saad, Meixi Zhang, Evangelos Panos and Christian Bauer from the Laboratory for Energy Systems Analysis are involved in the analyses. "EU legislation is a very important driver for the accelerated introduction of SAF," says Evangelos Panos. "We are investigating what impact it could have on the European production of synthetic fuels and on other sectors of the energy system. We are also evaluating the different objectives of this regulation and the different forecasts for demand in aviation." Meixi Zhang adds: "SAF production needs a lot of electricity from renewables, mainly led by its input demand for green hydrogen. It is therefore important to understand how certain blending quotas will affect the entire energy system given various aviation demand projections and SAF import potentials."
Despite all the uncertainties, one thing is very clear from the results of the work so far: even SAFs are not the panacea that will make air traffic climate-sustainable in one fell swoop, in view of the predicted global doubling of traffic by 2050. The quantities required are enormous. In addition, we must not forget the warming effect of soot particles, condensation trails and cloud formation caused by aircraft, which will increase as air traffic rises, despite using SAF.
Romain Sacchi makes it clear: "if we continue to fly more and more, climate neutrality will remain an illusion until 2050. It is extremely unlikely that there will be enough electricity from renewables and enough plants for water electrolysis and CO2 capture for SAF production." Even if this were the case, to compensate for the warming caused by condensation trails and cloud formation, a huge amount of CO2 would have to be extracted from the air and permanently stored. Possible storage locations for extracted CO2 are also a limited resource.
Nevertheless, the topic of SAFs should remain at the top of the PSI research priority list, says Christian Bauer: "SAFs can make an important contribution to more climate-sustainable flying. However, production must become significantly cheaper and more energy efficient." This is precisely where the PSI Laboratory for Energy Systems Analysis can play a part.
The SynFuel initiative, financed by the ETH Domain, and in which various research groups at PSI and Empa are involved, will be completed in late 2024.
Metafuels
The Metafuels project, carried out at the PSI ESI Platform, aims to construct a pilot plant for the cost-effective and efficient production of SAF, thereby acceleratiing the commercialization of the process. The aviation fuel, "aerobrew," is created through an innovative process patented by PSI and Metafuels.
For this project, Karin Treyer and Bettina Eberle at the Laboratory for Energy Systems Analysis are calculating the environmental impact of aerobrew production. "In doing so, we will also answer the question of where geographically the individual process steps are best situated. This depends, on the one hand, on where resources such as electricity from renewables, CO2 and water are available at low cost, and on the other hand, on how transport, storage and logistics are organized right up to the airport,” explains Treyer.
The Metafuels project is funded by the company Metafuels and by the Swiss Federal Office of Energy and is expected to run at least until 2026.
SWEET-ReFuel.ch
The ReFuel.ch project, which was launched in late 2023, is dedicated to similar questions as the SHELTERED project (described above). In addition to technical, economic and environmental aspects, the focus is also on political and social issues, as well as practical implementation. The project seeks to answer questions such as
- What political framework conditions are necessary to make the required quantities of synthetic fuels available as quickly as possible?
- How can problematic dependencies of Switzerland on other countries be avoided?
The reFuel.ch consortium consists of researchers at nine institutions. The key partners for LEA scientists are the Laboratory for Urban Energy Systems at Empa and the Energy and Process Systems Engineering Group at ETH Zürich. Practical relevance is ensured by means of concrete case studies and partners in Oman and Spain.
The ReFuel.ch project is part of the SWEET program, funded by the Swiss Federal Office of Energy.
ESYN
The ESYN project focuses neither on air traffic nor on Switzerland, but on motorized private transport in Africa. A collaboration between ETH Zurich—the Chair of Energy Systems Analysis, the Climate Policy lab, and the Energy and Technology Policy Group—and PSI is investigating how passenger road transport in Africa can be made as environmentally sustainably as possible. Despite the frequent lack of infrastructure for power supply and battery charging, are battery-powered electric cars and two-wheelers an advantage here too, as they are in many European countries, or would synthetic gasoline in imported used cars be better?
"I think it is very important that we address the question of how we can realize a clean transport sector in Africa," says Christian Moretti, who is co-leading the work at the PSI Laboratory for Energy Systems Analysis. "In contrast to Europe, we expect enormous growth there, and the opportunity to grow in a sustainable way must not be missed."
The researchers are creating a dynamic system model to analyze the competition between electric vehicles and synthetic fuels. This model will consider both the existing vehicle stock and the demand for new and used vehicles. In addition to the costs of vehicles and fuels, the model will also consider the need for new infrastructure and practical feasibility. Greenhouse gas emissions and other environmental impacts will be calculated using life cycle assessments. Finally, the project will examine how political measures can influence the course and results of the necessary transformation processes.
The ESYN project is part of the ETH Mobility Initiative.
Related recent publications:
Boyce, J., Sacchi, R., Goetheer, E. & Steubing, B. (2024). A prospective life cycle assessment of global ammonia decarbonisation scenarios. Heliyon. doi: 10.1016/j.heliyon.2024.e27547
Wei, S., Sacchi, R., Tukker, A., Suh, S. & Steubing, B. (2024). Future environmental impacts of global hydrogen production. Energy & Environmental Science. doi: 10.1039/D3EE03875K
Saad, M. D., Terlouw, T., Sacchi, R., Bauer, C. (2024). Life Cycle Economic and Environmental Assessment of Producing Synthetic Jet Fuel Using CO2/Biomass Feedstocks. Environmental Science & Technology. doi: 10.1021/acs.est.4c01578
Sacchi, R., Becattini, V., Gabrielli, P. et al. (2023). How to make climate-neutral aviation fly. Nature Communications 14, 3989. doi: 10.1038/s41467-023-39749-y
Treyer, K., Sacchi, R., Bauer, C. (2021). Life Cycle Assessment of synthetic hydrocarbons for use as jet fuel: “Power-to-Liquid” and “Sun-to-Liquid” processes. Paul Scherrer Institute (PSI), Villigen, Switzerland. Commissioned by the Swiss Federal Office of Civil Aviation (FOCA). https://www.psi.ch/en/media/72878/download?attachment?attachment