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280 million cars are registered in Europe, almost all of them run on petrol or diesel. Ships and planes also rely heavily on liquid, petroleum-based fuels. Thanks to renewable fuels — also called efuels — all of these could be operated in a carbon-neutral manner in the future.

Take Germany as an example. On average, a German car owner uses around 900 to 1,000 liters of fuel per year — a considerable contribution to the overall German carbon footprint. According to many experts, little will change over the next 20 years, which is how long it is at least going to take to extensively switch to electric cars. But private consumers are not too keen on changing their cars to electric, even with heavy government funding. Only about 400,000 electric cars are registered in Germany, meaning the majority of the 48 million cars will continue to use liquid fuels. So do the 3.3 million trucks, commercial and recreational ships, and the complete aviation sector. This represents a massive market for climate-neutral fuels.

The declared goal of the federal government is to make Germany climate neutral by 2050, including the transport and traffic sectors. Electric cars could make a significant contribution to this energy and transport turnaround if they really use renewable energy. But since this is highly unlikely, in part because Germany is getting rid of its nuclear power plants, e-mobility will have to be supported by other carbon- neutral technologies. Even the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) assumes that synthetic fuels can make an important contribution to reducing greenhouse emissions, especially in heavy haulage and long-distance traffic sectors. These new and carbon-neutral fuels are even more important since it is very unlikely that planes and ships can be fully electrified in the near future. One might even argue that technological hurdles for the electric transformation of these areas are just too high. With renewable fuels, however, all of these modes of transport can be made carbon-neutral.

What are renewable fuels?

Renewable fuels are produced using renewable energies. Put simply, they combine hydrogen from green electricity generation with CO2, for example from industrial exhaust gases or from the air, to create a carbon-neutral, gaseous or liquid hydrocarbon. The terms power-to-X (PtX), power-to- liquid (PtL), or biomass-to-liquid (BtL) describe the various end products. Simply put, PtL (Power-to-Liquid) is a process for converting electricity into hydrogen and combining that with carbon dioxide and gas into various liquid synthetic fuels such as gasoline, diesel, kerosene, and methanol.

The electrolysis of water generates hydrogen, which can either be used directly as fuel (for fuel cell vehicles) or can react with CO2 to form various gaseous (power-to-gas) or liquid (power-to-liquid) hydrocarbons. These synthetic fuels can be used in conventional internal combustion engines. This creates the possibility of making heavy-duty and long- distance traffic carbon-neutral, which, at the moment, is still not attainable with electric motors and current battery technology.

The energy sources produced by the BtL (biomass to liquid) process also have a better carbon footprint than fossil fuels. BtL products, when used in an engine, release only the amount of CO2 that they previously absorbed from the atmosphere. However, BtL fuels only make sense if the biomass required for their production does not compete with forest or cultivation areas for food. The second generation of biogenic fuels avoids that competition because they use algae, wood waste, straw, or sewage sludge. In principle, any carbon-containing biomass is suitable as a raw material for BtL.

How are synthetic fuels and renewable fuels made?

Synthetic fuels use CO2 captured from the atmosphere and biogenic waste and other carbon suppliers, like garbage, sorting residues, or processed waste. In this way, waste is no longer used just to generate heat by burning it, but serves as part of the value chain for fuel production.

During production, pure synthesis gas is generated first before being converted into new plastics or synthetic fuels. At the heart of the technology is a reactor in which the carbonaceous raw materials are chemically converted with oxygen and water vapor at temperatures of over 1,000 degrees Celsius. The resulting synthesis gas is a mixture of carbon monoxide and hydrogen. In a second step this is catalytically converted into a wide range of gaseous and liquid hydrocarbons. This process is known as the Fischer- Tropsch synthesis and was invented in 1925 and originally used to liquefy coal. Depending on the catalyst and target product, the synthesis takes place at temperatures of around 160 to 300 degrees Celsius and pressures of up to 25 bar.

OME — oxymethylene ether — is also fascinating, because in addition to reducing fine dust emissions, nitrogen oxide emissions are also reduced when it is burned.
In addition to liquid, low-sulfur synthetic fuels, the Fischer- Tropsch synthesis also produces synthetic engine oils and hydrocarbons. These hydrocarbons can be synthesized into gasoline, diesel, methanol, and further into OME. OME differs in its chemical structure from conventional petroleum-based fuels due to the stored oxygen. That is why OME burns practically free of fine dust and soot. That makes it extremely interesting as a fuel. The enormously complex and costly exhaust gas treatment of diesel engines could be reduced to a minimum with OME.

Renewable fuels burn cleaner and are suitable for all engines

In general, renewable fuels lack nitrogen and sulfur compounds as well as aromatic hydrocarbons, all of which contributes to lower pollutant emissions. Another key advantage: synthetic fuels do not differ technically from their conventional counterparts. They can even be used in classic cars and sold via the existing fuel infrastructure — in their pure form or as an add-on. However, OME, for example, is not compatible with all the sealing materials used in an engine. The technical adaptation of vehicle fuel systems and an expansion of the refueling infrastructure would appear to be very sensible in this case because of the many advantages OME offers. In order to prevent damage to the engines in existing vehicles, the properties of synthetic fuels must conform to the standards for diesel and gasoline. Synthetic fuels now have their own standard, EN 15940, which makes it easier for manufacturers to develop engines in new vehicles that are suitable for synthetic fuels.

Adding-on renewable fuels can have a great effect on fighting climate change

Even if renewable fuels are not initially used in their pure form, they can have a major impact on reducing CO2 and pollutant emissions in the transportation sector when being added to normal fuel, a process known as blending. The average car on Germany’s roads is about eleven years old. The carbon emissions of the transportation sector could be quickly and sustainably reduced with blends within the currently valid fuel standards. Renewable fuels can be added on in the future but this is already happening with so-called biofuels. One example is the diesel fuel R33, a mixture of conventional diesel and 33 percent bio- components, which consists of hydrogenated vegetable oil and used cooking oil methyl esters.

Renewable fuels could use the existing infrastructure

Standard gasoline can be made more environmentally friendly by adding bioethanol. In order to reduce the CO2 emissions of vehicles with gasoline engines, premium fuel with the addition of E10 was introduced in Germany in 2011. It includes ten percent of biofuel, made up of straw, leaves, sawdust, scrap wood, or sugar cane. Since those ten percent replace the corresponding amount of fossil fuel, it respectively lowers carbon dioxide emissions. From a strictly technical point of view, this is not a synthetic fuel, as it is made from biogenic material and not from electricity. Nevertheless, it is an important contribution to the defossilization of the mobility sector. For more than ten years now, all new passenger cars with gasoline engines have been suitable for E10, but even the owners of older cars, with some exceptions, can use E10.

One company that has been operating right at the cutting edge of synthetic and renewable fuels for years is P1 in Berlin. CEO Martin Popilka explains the current situation: “State-of-the-art internal combustion engines and carbon- neutral fuels can work together to further a climate-neutral mobility. We could start reducing CO2 emissions immediately by using an increasing percentage of renewable components in normal gasoline”. The German filling station network currently comprises around 14,500 filling stations. Blended fuels such as E10 and R33 can easily be stored in the large underground tanks that were previously used for conventional petrol and diesel.

The potential of renewable fuels is great

If we take a look across all the mobility sectors, it seems clear that renewable fuels and electromobility will have to complement each other in the future. Only an orchestrated interaction can guarantee significant progress on the way to emission-free mobility, even taking into account the costs. In 2017, Bosch calculated that, depending on the cost of the regenerative energy used, a hybrid car powered by renewable fuels with a maximum mileage of 160,000 kilometers is cheaper than an electric car over the same distance. And not only that, such a vehicle could use the existing filling stations and the automotive industry and its suppliers can continue to use the existing know-how in combustion technology in the future.

Renewable fuels as energy storage

Renewable fuels, just like conventional liquid fuels, can be easily stored and transported. This does not apply to electricity generated from hydropower, wind, and solar energy unless, of course, one uses the renewable electricity to produce synthetic fuels. Synthetic fuels can become an important part of the energy transition. At the moment, their production is still time-consuming and expensive, because large-scale production facilities are in the process of being set up. But a market ramp-up and a favorable price development in the electricity sector could ensure that renewable fuels become significantly cheaper. According to current studies, fuel costs of EUR 1.00 to EUR 1.40 per liter can be realized in the long run (excluding energy tax).

Figures from German think tank “Agora Verkehrswende“ from 2018 show that the production of synthetic liquid fuels based on wind power plants in the North Sea cost around 20 to 30 ct/kWh in the early 2020s — conventional gasoline manages around 6 ct/kWh. In comparison, a combination of photovoltaics and wind power would be around 40 percent cheaper when set up in North Africa. In the medium to long term, the costs of synthetic fuels will be significantly reduced due to economies of scale and technical progress and could — this, of course, being an optimistic assumption — drop to as little as 10 ct/kWh. In this case, synthetic fuels would only be marginally more expensive than conventional ones. In order to make it cost-neutral for the end customer, the energy tax could be adjusted.

Vehicles powered by renewable fuels from green electricity are climate-neutral, with a correspondingly large impact on CO2 emissions. As early as 2017, Bosch experts calculated how significant the contribution to limiting global warming would be with regard to Europe’s passenger car fleet alone: By 2050, the consistent use of renewable fuels and synthetic fuels in addition to electrification could save up to 2.8 gigatons of CO2. CO2 emissions in the traffic sector in the past were 163.5 million tons in Germany alone. By 2030, this sector is expected to emit only 98 to 95 million tons of carbon dioxide.

The industry is starting to rely on renewable fuels

Many players in the automotive industry want to tackle CO2 reduction with the help of renewable fuels, Audi being one of the pioneers. A pilot project was started back in 2011 in Werlte, Lower Saxony. At that plant Audi and its industrial partners have produced climate-neutral, synthetic e-gas, but not renewable fuels so far.

Porsche wants to take this development one step further and aims at offering its sports cars, especially the 911, with the option of using synthetic fuels. Michael Steiner, Head of Development at Porsche, said in an interview with the magazine Automobilwoche: “If we make good progress, all 911 Carrera models sold worldwide could be supplied with 100 percent renewable fuels as early as 2024”. When delivered, every Porsche 911 would then run on synthetic fuel. Porsche also has in mind the many classic models that are driven by the brand’s enthusiasts and it plans to offer them renewable fuels as well. Around 75 percent of all Porsches ever built are still around today, and all have internal combustion engines. Naturally, Porsche aims to increasingly use renewable fuels in motorsports as well.

Germany is only one example of how synthetic fuels are gaining rapidly in importance internationally. This is the result of political decisions made recently by many countries, including China. In the current Chinese five-year plan, the gigantic empire is looking at new mobility perspectives. The Chinese idea of banning cars with internal combustion engines from 2030 onward, is finally off the table. The new timeline states that petrol and diesel cars will be banned from the salesrooms in 2060 instead. Nevertheless, the internal combustion engine will still have to make its contribution to reducing emissions, and this can only be achieved with carbon-neutral fuels. In addition to electric cars, China also explicitly wants to harness hydrogen and climate-neutral synthetic fuels in its drive toward clean mobility. By the way, in Mandarin, renewable fuels are spelled by these symbols 电子 燃料. It’s something we may come across more often in the future.