What are reFuels and how do the terms „HVO“ and „E-Fuel“ relate to each other?
Dr. Toedter: The term „reFuels“ is a name describing all fuels that can be produced from renewable sources and used in existing infrastructure. HVO, produced from residual and waste materials, is one example of this group of fuels. The production uses waste that already contains a significant amount of energy. However, only a small amount of additional hydrogen is required. Therefore, HVO requires less energy than e-fuels (power-to-liquid, PtL). Fischer-Tropsch fuels, synthesized at locations with abundant sunshine and wind, are an example of the PtL process. As diesel fuels, both comply with DIN EN 15940 for paraffinic diesel. The following graphic from the Karlsruhe Institute of Technology (KIT) describes the reFuel concept in more detail. Electricity-based fuels, so-called e-fuels, also belong to the reFuels group. The KIT graphic uses an analogy with an apple and an orange. E-fuels are preferably produced in sunny and windy, mostly southern countries (analogy: orange). In contrast, HVO requires little electricity and can therefore also be produced in Nordic countries (analogy: apple).
Note from eFuelsNow::
The map displays the following reFuels:
=> HVO diesel fuels
=> Bionaphtha-based gasoline
E-fuels (gasoline and diesel) will also be displayed in the future (date unknown).
What are the differences between HVO and biodiesel?
Prof. Willner: Both are diesel substitutes. However, they differ chemically. Biodiesel fuels are fatty acid methyl esters (FAME) that still contain approximately 11% oxygen by weight in their molecules. It conforms to DIN EN 14214. HVO (Hydrotreated Vegetable Oil) is produced exclusively from pure liquid hydrocarbons. It contains no oxygen. Unlike biodiesel, pure HVO fuel has an unlimited shelf life. It complies with DIN EN 15940. HVO contains no aromatics. It is crystal clear, almost odorless, and burns cleaner than biodiesel or fossil diesel. Furthermore, it is resistant to diesel bug. HVO can also be used without problems in conventional diesel engines in its pure form. This is not the case with biodiesel engines.
Are there also fuel-based alternatives (similar to HVO) for gasoline engines?
Dr. Toedter: Yes, fuels based on residual materials are also available for gasoline engines. Currently, E10 fuel is most often supplemented with bionaphtha.Gasoline-powered fuels can be produced via both the PtL route (usually using e-methanol) and the BtL (biomass-to-liquid) route. Bio-methanol, based on biogenic residues and waste materials, is a basis for both synthetic gasoline from bionaphtha and gasoline produced via methanol-gasoline. Gasoline engines have higher requirements for knock resistance.
Anmerkung eFuelsNow: You can also find gas stations offering these types of fuel in the app.
How efficient is HVO?
Prof. Willner: First, we need to clarify what kind of efficiency we’re talking about. In terms of cost, time, electricity, and resource efficiency, HVO is unrivaled. Existing diesel vehicles can immediately contribute to climate protection without significant time investment, without engine modifications and by utilizing existing infrastructure. This results in the highest CO2 savings efficiency. HVO is also considerably more effective than electric vehicles in terms of electricity efficiency. This is because the waste materials already contain a lot of energy. Therefore, very little additional energy is required for production.
How efficient is e-fuel?
Dr. Toedter: The concept of efficiency has several levels. In terms of cost, time, and resources, e-fuels are efficient fuels because closed carbon cycles within existing infrastructure contribute immediately to climate protection. However, e-fuels (power-to-liquid, PtL) require a significant amount of electrical energy for hydrogen electrolysis. CO2 from the air is captured via direct air capture (DAC) or from industrial plants. This is used to create a high-energy-density energy storage system. The electrical energy required for this should be sourced from favorable locations, meaning sites with high yields of wind and solar power.
Many efficiency calculations assume that e-fuel would be produced in Germany. However, for yield reasons, this would only be feasible at a few locations. At these favorable locations, the significantly higher yield factor offsets the conversion losses. Globally, there is no shortage of energy from renewable sources. The main challenges are transportation and energy storage. In this case, the energy is stored as fuel. Even with directly used electrical energy, losses due to conversion and auxiliary equipment must be taken into account.
Note from eFuelsNow: Electricity is a very valuable form of energy, instantly usable energy that doesn’t occur naturally. Electricity always requires pre-transformation, which inevitably results in losses. Whether these thermodynamic processes take place under the hood of a car or on the outskirts of a city is completely irrelevant.
Are reFuels also used in aircraft? Wouldn’t it be more sensible to concentrate solely on the marine and aviation sectors?
Prof. Willner: Many airlines already fly with renewable kerosene, similar to HVO. Companies like Neste are already producing it on a large scale. However, producing kerosene in isolation makes no sense because its manufacture always generates byproducts, in the gasoline and diesel sectors. Furthermore, fuel consumption in the shipping and aviation sectors is much lower than in road transport. Focusing on the small application areas of aviation and shipping would massively slow down climate protection, precisely where the impact for CO2 savings is greatest, namely in road transport. Moreover, fuel will become cheaper for everyone if all byproducts generated during production can be sold and the facilities are used optimally.
How much of global traffic can be covered by renewable fuels such as HVO and e-fuel?
Prof Willner: In principle, the entire fuel demand for all global transport sectors (cars, ships, airplanes, etc.) can easily be covered with waste-based fuels and e-fuels over a period of 30-40 years. According to a projection by the company Neste, using all types of alternative fuels could supply approximately 40% of global fuel demand by 2040. These figures align with potential estimates from the Hamburg University of Applied Sciences (HAW Hamburg). Additionally, a study has identified a significant HVO potential of 200 megatons per year based on jathropha. This could cover the entire fuel demand of the EU. Jathropha is a plant that grows on marginal soils in desert fringe areas and therefore does not cause any food-fuel conflicts. This opens up export opportunities for previously disadvantaged countries. Furthermore, the cultivation of jathropha offers additional CO2 sequestration potential, as the plants are grown in areas where no vegetation previously existed. This results in a negative CO2 footprint for the fuels produced. Looking beyond the next 40 years, it’s possible to meet the entire global energy demand of humanity with renewable energy. This also applies to fuel requirements, of course. However, this requires appropriate regulations.
Does HVO have a „food versus fuel“ conflict? What is HVO made from?
Dr. Toedter: HVO is produced from residual and waste materials. These can include used cooking oils, inedible food scraps, tailings, sewage sludge, etc. Many residual materials contain carbon and hydrogen compounds that can be made usable again through cracking and hydrogenation. Food versus fuel conflicts do not exist with HVO, as these residual materials are not cultivated. Perhaps only Jatropha, which grows on poor soils, would be such a case. However, this plant is not yet in use, and the land required for its cultivation cannot be used for food production.
Prof. Willner (added): Since HVO is currently produced exclusively from waste biomass, this problem does not exist here. This fact is reviewed and documented annually in the evaluation report of the Federal Office for Agriculture and Food.
Does HVO have a palm oil problem?
Prof Willner: Palm oil is not used for biodiesel or HVO production in Europe. Since 2023, it has no longer been counted towards greenhouse gas emissions quotas. This is documented for Germany in the evaluation report of the Federal Office for Agriculture and Food.
Can HVO100 be used in any diesel vehicle and do I need any lubricating additives?
Dr. Toedter: HVO is a very compatible fuel that can be used in 99% of all diesel engines. There are only very few cases where problems might arise, such as with rare high-performance diesel engines. We are not aware of any specific examples. The Karlsruhe Institute of Technology (KIT) also conducted a long-term study over 800,000 km in a transport company with very positive results. We also operate our institute’s fleet and our private cars exclusively on HVO100. The fuel meets or even exceeds standard diesel in all its properties. It is only 6% lighter. Due to the higher cetane number, however, there are only minor differences in fuel consumption (if any). Positive long-term experiences from Scandinavia and California already exist. The fuel has been sold there for over 10 years. Due to very high legally mandated blends, it is used millions of times daily, regardless of manufacturer approval. There are also no differences in lubricating properties. Because HVO100 at petrol stations complies with the legal standard DIN EN 15940. Lubricating additives are part of the regular production process. As a result, HVO100 sometimes even achieves better lubricating properties than fossil diesel.
Can e-fuels be used in any gasoline engine?
Dr. Toedter: E-fuels are fuels without a fixed crude oil base. These fuels can be optimally adapted to engine requirements. Therefore, there will be no problems with e-fuels in the vehicle fleet. Tests have already begun with positive results.
Can reFuel gasoline (e.g., made from bionaphtha) be used in every gasoline engine?
Dr Toedter: Gasoline with bio-based additives (e.g., bionaphtha) is very compatible with diesel fuel, similar to HVO. However, the supply is still very limited. Therefore, such fuels are usually blended with ethanol to achieve greater CO2 reduction. This is most often an E10 blend, which is compatible with 95% of all current gasoline vehicles. Nevertheless, it is important to ensure that the fuel has been approved according to DIN EN 228. This approval, however, relates to the ethanol content and not to the bionaphtha content!
When will e-fuels be available at gas stations?
Dr Toedter: The technology is already tried and tested and established. The only decisive factors for its scaling up are economic and regulatory frameworks. Equal consideration of greenhouse gas reduction in all sectors, along with taking import requirements into account, would accelerate the scaling up. Outside the EU, several facilities are in operation and even more are under construction.
Why is the German HVO network not as well developed as in Italy?
eFuelsNow: This is related to regulations in Italy, which have always been significantly more open to different technologies. Furthermore, Germany (as of the end of 2025) is one of the last countries where Super E5 is still legally required. This blocks tank capacity. However, 95% of all registered gasoline vehicles could easily run on E10. Ultimately, the expansion of the refueling network also depends on the GHG quota in the fuel sector. In the past, this quota was considerably less ambitious in Germany than in other countries. This demonstrated a clear contradiction, as a reduction in CO2 emissions was being demanded very loudly.
The video shows the development of the HVO refueling network between 2023 and January 2025. Current figures can be found in the app and on the HVO refueling station map (website).
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