Power to X Engineering From Smokestack to Fuel Pump: “Clean” Fuel from Water and CO2

Eco-friendly, limitless and CO2-neutral: Can synthetic fuel become the future of mobility? Power-to-X projects could be used to convert surplus electricity from renewable resources into clean synthetic fuels. While decision makers and politicians are still discussing the concepts feasibility, German engineering experts from Chemieanlagenbau Chemnitz (CAC) show what can be done …

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Powering the future of mobility: Synthetic fuels can become an eco-friendly alternative to crude based gasoline or battery powered electromobility solutions. A German engineeri­ng company shows the possibilities.
Powering the future of mobility: Synthetic fuels can become an eco-friendly alternative to crude based gasoline or battery powered electromobility solutions. A German engineeri­ng company shows the possibilities.
(Source: ©nexusseven - stock.adobe.com; CAC; [M] Herkersdorf)

Gasoline keeps the world moving: For over a century, the hydrocarbon mixture has been powering cars, machines, boats and aircraft engines. Today, US refiners alone produce nearly ten million barrels each and every day. But now, attention shifts towards the CO2 balance of refined crude oil. Is it high time to phase out internal combustion engines and go all in for electro mobility? The pitfall of battery driven cars are well known — weight, range issues and, of course, cell production are enough to give even the most ardent fans of electric vehicles plenty to think about. Could there be an easier way? For example by using synthetic fuels to take advantage of existing infrastructures and technologies that have been refined for decades?

This idea has sparked the ingenuity of researchers: A correspond­ing process, the Fischer-Tropsch synthesis for coal liquefaction, was developed as early as 1925. Although this approach no longer plays an important role in Europe or the US, the idea of creating liquid fuel from synthesis gas lives on. Faced with limited oil reserves, plant and process engineering company CAC started working on synthetic fuels in the early 2000s.

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How Green is Green Fuel Really?

By 2010, the engineers had a­chieved significant breakthroughs, resulting in the manufacture of liter quantities of synthetic gasoline. Their method, dubbed STF (Syngas-to-Fuel), converts various streams of raw gas into synthesis gas. This is then used to produce methanol, which is catalytically converted to gasoline.

Company CEO Joachim Engelmann is certain that their alternative fuel is equivalent or even superior to crude based gasoline, with for example significantly higher oxidation stability. Today, the engineering company from Chemnitz, Germany, has patented the process in Australia, China, India, Eurasia, Canada and Germany. Nonetheless, production of synthetic fuels is a very complex process — and the environmental balance barely differs from that of crude based materials. Would it be possible to produce gasoline without any fossil raw materials at all? For example from carbon dioxide, electricity and water?

Green Gasoline Thanks to STF

Power-to-X is a label for different processes designed to produce a wide range of raw materials with electric energy. Thus, CAC’s management came up with an idea: Could the STF process be used for the production of gasoline virtually from thin air and sunlight? But the leap from lab and technical center testbeds to industrial scale production made it necessary to rethink the reactor design and process control. Engelmann talks about a “decade of suffering” before the process was market-ready.

The idea is that STF-gasoline, which is 1:1 interchangeable with fossil fuel, could become a driver for green technologies: “Synthetic fuels are the future of mobility,” believes Dr. Mario Kuschel, Business Unit Manager Process Engineering at CAC. “We assume that the car of the future will increasingly run on synthetically manufactured gasoline or diesel.” And this is not just a question of preference: The renewable proportion of fuel must reach 14 % (twice the current level) in Europe by 2030, the Renewable Energy Directive (RED II) states. “In addition to emissions cuts, automotive manufacturers can continue to develop their engines,” says Kuschel. Although research is under way on alternatives like battery-electric drives and fuel cells, closer investigation reveals that the greenhouse gas potential of these options still remains high. “Our process enables the almost climate-neutral production of gasoline, as we only use CO2, water and electricity,” explains the PhD process engineer.

From Smokestack to Fuelpump

Unlike Syngas-­to-Fuel, CAC’s Power-to-X process uses methanol produced from hydrogen and carbon dioxide. In an upstream electrolysis process, water is split and used for hydrogenation of the CO2. The resulting methanol is converted isothermally to gasoline. The quality and composition of the product can be influenced very directly as a result, explains Joachim Engelmann. CO2 required for the production of the hydrocarbons is sourced simply from the air — or, more specifically, from industrial waste gases.

If carbon dioxide is captured directly in the smokestack, almost no waste gas is produced — making the so-called carbon capture a win-win situation for both, the industry and the production of fuel. This just leaves the energy demands, with electrolysis in particular, requiring large amounts of electricity. The environmental balance can only become positive if this electricity comes from climate-neu­tral sources (like regenerative or nuclear energies).

For a model project, CAC has worked together with Mitsubishi (MHPSE) to develop a complete process that uses electricity from hydroelectric power for the almost CO2-neutral production of high-­octane fuel. “The use of carbon dioxide for the production of synthetic gasoline is a unique selling point for our technology,” says Stephan Schmidt, Product Manager Synthetic Fuels at CAC. “Although there are competitors who are also researching synthetic fuels, they are still obtaining the CO2 from coal or natural gas.”

A New Career for Waste Gas

The idea of using waste gas for fuel production turns an unwanted by-product into a sought-after commodity. He believes that industrial companies would not need to discharge the carbon dioxide into the environment at all, but instead could direct it straight back into the cycle as a raw material. The savings could be offset with emission certificates. “However, the legal framework is not set up to our advantage,” says Schmidt, who hopes that the legislation will classify synthetic gasoline as a clean fuel. Engelmann sees the biggest potential in point sources like power stations, steelworks or cement plants. “If we can produce a liter of gasoline from three kilogram of CO2, the potential is considerable. We already drew up a concept for a 250,000 tonnes per year plant years ago — we are ready for large-scale industry,” the engineering specialist is confident.

The product could become even “cleaner”, if the CO2 is sourced not from industrial waste gases but instead from biogenic origins. With electricity from alternative energies, the vision of environmentally friendly gasoline is almost here: “There are many interested parties in our process,” says Kuschel, “but no large-scale plants have been built yet.” Just recently the demonstration plant on the premises of Freiberg University of Mining and Technology produced twelve tons of synthetic gasoline for tests with automotive manufacturers. The work is sponsored by the German government and the Free State of Saxony, but CAC has also invested a seven-digit amount in the project out of its own funds.

“We believe that we have developed something totally unique,” explains Engelmann, for whom Carbon-to-X processes have become a matter of great personal importance. “We employ highly qualified process engineers in the field of R&D. We see the potential and are convinced that the technology has the power to break through. It is a great deal of fun to work together with these specialists to bring pioneering technologies onto the market.”

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