How Carbon-neutral E-fuels Work

Wind, Wheels and Watts

The e-gas plant in Werlte is the first in the world to combine hydrogen electrolysis with methanation (the hydrogen gas and carbon dioxide reaction), but that's not the only innovation. The electricity used in the electrolysis reactions will begin as strong breezes whipping over the North Sea, the site of three large-scale offshore wind farms. There, Audi has built four turbines, each with a capacity of 3.6 megawatts. Together, the turbines should generate 53 gigawatt-hours of electricity each year [source: Audi USA]. This renewable energy will be used in three ways [sources: Audi USA, Fraunhofer-Gesellschaft]:

  1. Audi has earmarked a portion of this energy for its e-tron electric vehicle program. The company estimates it can harness enough energy from its wind turbines to produce 1,000 Audi A1 e-tron models and operate them for 6,210 miles (10,000 kilometers) per year.
  2. The rest of the energy -- about 20 gigawatt-hours -- will flow to the e-gas plant in Werlte. There, the renewable electricity will power the hydrolysis that splits water into oxygen and hydrogen gas. In the future, the hydrogen could find a home in vehicle fuel cells, but in the next several years, it will serve as one of the main ingredients to make synthetic methane, or e-gas. The e-gas will enter the natural gas supply and, ultimately, the fuel tanks of NGVs.
  3. The synthetic methane will also provide a storage function. Right now, wind farms like those in the North Sea often produce more electricity than the power grid needs at that moment. That electricity is lost if it can't be stored for future use. Enter e-gas, which can be diverted into Germany's vast natural gas infrastructure and then pulled back out, when needed, as a fuel source in power generation. By some estimates, the German natural gas network could hold the equivalent of 200 terawatt-hours of electricity -- enough to satisfy consumption for several months.

Audi didn't come up with this concept on its own. The process was developed by the Center for Solar Energy and Hydrogen Research Baden-Württemberg, in cooperation with the Fraunhofer Institute for Wind Energy and Energy System Technology. Other partners include Solar Fuel Technology, which has a facility next to the e-gas plant. Waste heat generated during electrolysis and methanation in the Audi plant will be used in the Solar Fuel Technology facility, tremendously enhancing overall efficiency.


The car company celebrated the topping out of its Werlte facility in December 2012 and expects e-gas production to begin in 2013. This will be followed by delivery of its new Audi A3 Sportback TCNG vehicles, which will begin arriving at dealerships in late 2013. Audi also plans to launch a second TCNG model, based on the A4, in 2015. By then, you can expect to see more and more natural gas vehicles on the road. Both Chrysler and General Motors have launched natural-gas versions of their heavy-duty trucks. And Honda will continue to promote its natural-gas Civic to consumers looking to save a little money and -- just maybe -- the planet.

Author's Note: How Carbon-neutral E-fuels Work

It's easy to mistake NGVs as a new concept, but they've been around a long time. My father, who worked in the West Texas oil fields in the late 1940s and early '50s, used to tell stories of guys running their beat-up trucks on natural gas. Wonder what those roughnecks would think today of synthetic methane or the new Audi A3 Sportback TCNG?

Related Articles


  • Atiyeh, Clifford. "Audi to open natural gas, hydrogen plant in 2013." MSN Autos: Exhaust Notes. Dec. 19, 2012. (Jan. 2, 2013)
  • Audi USA. "Audi balanced mobility." April 12, 2012. (Jan. 2, 2013);jsessionid=CD5CBC290206D63A734E3C332D5D7CA9?&id=2875&allImage=1&teaser=audi-balanced-mobility&mid=
  • Audi Worldwide. "Topping-out ceremony for the Audi e-gas plant." Dec. 13, 2012. (Jan. 2, 2013)
  • Consumer Reports. "The natural-gas alternative." March 2012. (Jan. 2, 2013)
  • DeMorro, Christopher. "Audi E-Gas Claims Carbon Neutrality." Gas 2. Oct. 9, 2012. (Jan. 2, 2013)
  • Durbin, Dee-Ann. "Natural Gas Vehicles Flooding Market As Gas Prices Rise." Huffington Post. March 7, 2012. (Jan. 2, 2013)
  • Electric Drive Transportation Association. "Electric Car Sales." (Jan. 2, 2013)
  • Fraunhofer-Gesellschaft. "Storing green electricity as natural gas." May 5, 2010. (Jan. 2, 2013)
  • Millikin, Mike. "Audi unveils e-gas project: synthetic methane from the methanation of green hydrogen; series production of CNG models in 2013 powered by e-gas." Green Car Congress. May 13, 2011. (Jan. 2, 2013)
  • Natural Gas Vehicles for America. "About NGVs." (Jan. 2, 2013)
  • NGV Global. "Current Natural Gas Vehicle Statistics." (Jan. 18, 2013)
  • Okulski, Travis. "This E-Fuel Works Just Like Gasoline But Is Entirely Carbon Neutral." Jalopnik. Oct. 4, 2012. (Jan. 2, 2013)