THE GND IS TOO CAUTIOUS:

The idea of turning air into liquid fuel may sound fantastical, but the underlying principle is as mundane as a head of lettuce. "It's the same thing that plants do with photosynthesis," says Roland Dittmeyer, leader of the project and director of the Institute for Micro Process Engineering at KIT.

While the machine that I watched produce that energy-dense liquid in the forest clearing is just the first stage of a pilot program, the underlying technology could help reshape the battle against climate change. The project, called P2X, is part of the Copernicus Project, an initiative to prepare Germany for a carbon-neutral economy by 2050. The $40 million demonstration phase was supported by 18 research institutions and 27 industrial firms, including Siemens, Volkswagen, Shell, and ThyssenKrupp.

The process begins with a module, built by Climeworks of Switzerland, that extracts carbon dioxide from the ambient air. The device blows air over a filter that absorbs CO2 and then releases the gas in concentrated form when heated. An adjacent unit, built by a Dresden-based firm, produces hydrogen by splitting water molecules through high-temperature electrolysis. In the third module, built by a Swiss tech company, a reaction called Fischer-Tropsch Synthesis fuses the carbon and hydrogen to produce hydrocarbons, the same carbon chains that make up gasoline, kerosene, coal, and natural gas.

The science behind each step has been understood for decades; what's new is the fusion of the processes into a compact, efficient system. "Fischer-Tropsch has been known for 100 years," says Klumpp. "It's putting the steps together that's hard." The heat produced by the synthesis reaction, for example, is repurposed to optimize the temperature for electrolysis.

The hydrocarbon fuels in use today are extracted from the Earth. When they are burned, they release carbon dioxide that drives climate change. What's coming out of the tap in Karlsruhe is different. So long as the energy used to make it comes from renewable sources, this synthetic hydrocarbon mix -- the P2X team came up with the name "eFuel"-- is carbon neutral when burned. And if the hydrocarbons are turned into materials like plastic, the end product is carbon negative.

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