‘There’s no legally mandated exit from fossil fuels’: Expert discusses trade-offs between renewable fuels

Researchers at the Green Fuel Center (GFC) on the Technical University of Munich (TUM) Straubing Campus are working on the production of renewable fuels. Prof. Jakob Burger talks about the advantages of these alternative fuels and where they could possibly be put to use.

What is the GFC doing for the sustainable mobility of tomorrow?

Prof. Burger: Renewable fuels bind either bioenergy or renewable electrical energy. Each approach has its advantages and disadvantages. In contrast to e-fuels, the production of biofuels for example does not require any CO₂ which has been painstakingly extracted from the atmosphere. On the other hand, when producing e-fuels we can store surplus renewable electrical energy.

The GFC is investigating how we can couple these two approaches with one another. For example electric energy can be used to boost the production of biofuels. Or we can use biocatalysts to improve the production of e-fuels. This interdisciplinary approach promises significant improvements in efficiency. This kind of approach can produce for example bio-based aircraft fuels whose CO₂ footprint has been reduced by one third compared to the most environmentally friendly current bio-aircraft fuels, without a significant increase in costs.

A demonstration system at the GFC uses oxymethylene dimethyl ether (OME) as an alternative to fossil diesel fuel. What is OME and what makes it such a special fuel?

OME is a renewable diesel fuel which can be produced either as biofuel or as e-fuel. This means it has a flexible basis in terms of both raw materials and energy. The chemical structure is different from today’s fossil fuels, and it contains chemically bound oxygen. This means the fuel is extremely clean when it burns, and it’s neither toxic nor harmful to the environment. Although it can be used in any diesel engine, fuel lines and the engine control unit have to be adapted, since typically they’ve been highly modified to optimally accommodate standardized fossil diesel.

When will industrial production of OME begin?

One member of the substance class OME, known as OME1, could also be used as a fuel. It has already been in industrial scale production for a long time now and is used as a solvent in the chemical industry. We’ve also developed a process for the variant OME3-5, optimized for transportation applications, which is expected to begin industrial production beginning in 2025.

How realistic is the idea that, for example, ships could be powered solely with OME in the future?

There’s no legally mandated exit from fossil fuels. The pressure on the electricity market, for example, is completely different. OME in particular is an exceptional renewable fuel. It burns extremely cleanly, but it has limited fleet compatibility. This means it most likely will not be used in airplanes or in passenger cars. And I’m skeptical about OME as the main fuel in shipping on the high seas, since in general, no environmental regulations apply to the high seas. But when these ships enter metropolitan harbors or when construction machinery with diesel engines has to be operated in an urban environment, OME is a great option for real environmental protection.