Definitions of terms used
Transparency on the subject of eFuels
Transparency is the key to creating trust in new technologies. And openness to technology is the key to achieving the transport transition. At eFuels Forum, we attach great importance to providing you with all the information you need to make informed decisions. The terms “climate-neutral” and “CO2-neutral” are often interpreted differently. In addition, the German Federal Court of Justice (BGH ) ruled on June 27, 2024 that terms such as “climate-neutral” or “CO2-neutral” must be explained clearly and precisely in advertising so as not to mislead consumers.
We welcome this approach and have prepared our content accordingly. It is particularly important to us that you, the consumer, fully understand the information provided and can make informed decisions.
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New CO₂ emissions and the greenhouse gas balance
Here, “new CO₂ emissions” means CO₂ emissions added to the atmosphere through the use of fossil fuels. Burning carbon-containing eFuels also releases CO₂. Any potential reduction must be assessed over the entire life cycle against a specifically identified fossil reference fuel. The electricity and CO₂ sources, production, transport and use are particularly important. A CO₂ cycle alone does not demonstrate climate neutrality.
What are eFuels and how do they differ from fossil fuels?
eFuels (electricity-based fuels) are liquid synthetic transport and heating fuels produced from hydrogen and carbon dioxide using renewable electricity. The CO2 is captured either directly from the air or from industrial exhaust gases. This production process makes it possible to produce liquid fuels that can be used in existing combustion engines without requiring new vehicles or infrastructure.
During combustion, the carbon contained in the fuel is released as CO₂. Whether and to what extent greenhouse gas emissions are reduced compared with fossil fuel depends on the specific production pathway and its full life-cycle greenhouse gas balance. Key factors include the energy used, the source of the CO₂ used, and emissions from production, transport and use.
How are eFuels produced?
The production of eFuels is based on power-to-liquid (PtL) processes. Renewable electricity is used to produce hydrogen through electrolysis. This hydrogen, obtained using wind, solar or hydropower, is then combined with carbon dioxide using either the Fischer–Tropsch process or methanol synthesis to produce a synthetic fuel. It is crucial that the electricity comes from renewable sources such as solar or wind power in order to improve the CO2 balance.
How high are the pollutant emissions of eFuels?
The research report reFuels – Rethinking Fuels provides important data on the pollutant emissions of eFuels compared to fossil fuels:
Particulate matter emissions (PM2.5): The life cycle assessment analyses in the report show that eFuels often have lower particulate matter emissions (PM2.5) than fossil fuels. These lower emissions are due to the clean combustion processes and the higher quality of synthetic fuels, which cause less incomplete combustion and therefore less particle formation.
Nitrogen oxide emissions (NOₓ): The report highlights that nitrogen oxide (NOₓ) emissions can vary when using eFuels, depending on the type of synthetic fuel and the specific engine. In some cases, slightly increased NOₓ values were found, which may be due to differences in the combustion process between synthetic and fossil fuels. Despite these variations, the emissions of eFuels generally remain within the legal limits and can be further reduced by optimizing the engine technology.
Comparison of greenhouse gas emissions: The report’s life cycle analyses show that eFuels can have a significantly better balance in terms of new CO2 emissions, depending on the production process and electricity source used. New emissions can be significantly reduced, especially if renewable energies such as wind or solar power are used in the production process. This is also the assessment of the researchers and authors of the study GHG Saving Potential of E-fuels.
Source: Research report reFuels – Rethinking fuels
Source: GHG Saving Potential of E-fuels
In addition, the ADAC tested the pollutant emissions of vehicles powered by eFuels in 2022. Three vehicle models were examined:
- VW Golf VIII: “All test results confirm the engine’s very low pollutant emissions. In all cycles, emissions are well below the limit values, even in the very demanding highway cycle of the ADAC Ecotest. Particle emissions are extremely low with both fuels. NOₓ emissions are even reduced by around 40 percent with the electricity-based fuel.”
- Ford Fiesta: “In the test, the pollutant emissions are partly within the limit values. With the e-fuel from CAC, there is a slight deterioration in nitrogen oxides, but the percentage difference is so marginal (in absolute values) that it could also be due to measurement tolerances.”
- VW Golf VII: “With the E10 e-fuel from CAC, the emissions change only slightly. Despite a slight increase in nitrogen oxides and an increased number of particles in the exhaust gas, the values remain legally compliant.”
Source: https://www.adac.de/verkehr/tanken-kraftstoff-antrieb/alternative-antriebe/e-fuels-test/
Frequently asked questions about CO2 emissions from eFuels
Why is the efficiency of eFuels production not decisive, provided renewable energy is used?
The efficiency of eFuels production, meaning the number of kWh of electricity required, is not the decisive factor when production takes place in regions where renewable energy sources such as wind or sunshine are not scarce. In such areas, renewable energy is abundant, so eFuels production places no additional burden on the electricity grid and has no negative impact on the CO2 balance. It may therefore make more sense to produce eFuels in these regions than to focus exclusively on energy conversion efficiency.
How important are the transport and distribution of eFuels to the overall CO2 balance?
The transport and distribution of eFuels play an important role in the overall CO2 balance. Naturally, all CO2 emissions arising from transport and distribution must be included in the calculation of total emissions. To fully realise the environmental benefits of eFuels, these processes should be designed to produce as few emissions as possible, or none at all.
What happens if eFuels are produced using the current electricity mix?
Producing eFuels using the current electricity mix, which still contains a high proportion of fossil energy sources, is not appropriate. Electricity generation from fossil sources causes additional CO2 emissions that form part of the eFuels production balance. It is therefore crucial for eFuels to be produced with a very high share of renewable energy to fully realise their benefits in reducing CO2 emissions.
Conclusion and outlook
eFuels offer a promising opportunity to reduce new CO2 emissions in the transport sector, particularly in areas where switching to electric mobility is more difficult. It is important to continue following developments in this field and to use a combination of technologies to enable the best solutions for modern mobility.
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