Audi Makes Diesel out of Thin Air (and Water)

German automobile giant Audi has a pilot program to produce diesel from carbon dioxide pulled out of the air, combining it with hydrogen electrolyzed from water with electricity from wind turbines. According to Audi's website:

Production of Audi e‑diesel involves various steps: First, water heated up to form steam is broken down into hydrogen and oxygen by means of high-temperature electrolysis. This process, involving a temperature in excess of 800 degrees Celsius, is more efficient than conventional techniques because of heat recovery, for example. Another special feature of high-temperature electrolysis is that it can be used dynamically, to stabilize the grid when production of green power peaks.

In two further steps, the hydrogen reacts with the CO2 in synthesis reactors, again under pressure and at high temperature. The reaction product is a liquid made from long‑chain hydrocarbon compounds, known as blue crude. The efficiency of the overall process – from renewable power to liquid hydrocarbon – is very high at around 70 percent. Similarly to a fossil crude oil, blue crude can be refined to yield the end product Audi e‑diesel. This synthetic fuel is free from sulfur and aromatic hydrocarbons, and its high cetane number means it is readily ignitable. As lab tests conducted at Audi have shown, it is suitable for admixing with fossil diesel or, prospectively, for use as a fuel in its own right.

Audi also has a pilot plant that produces "e-gas," creating methane (natural gas) with a similar process. Natural gas can be used to power vehicles, heat homes, cook food, etc.

The "blue crude" idea is kind of cool, as it would allow existing vehicles to be powered by carbon-neutral fuel. But it's limited: when we start cleaning up our act and reducing carbon emissions, over time the level of CO2 will drop as the carbon dioxide is sequestered in animals, plants, the earth and the ocean.

The real promise of this process is the extremely efficient high-temperature electrolysis that creates hydrogen. Hydrogen can be used to power fuel cells, which emit water as their waste product. Fuel cells powered the Apollo moon missions: the astronauts drank the water. Fuel cells are used in cars like the Audi h-tron, the Toyota Mirai and the Honda Clarity. Fuel cells can also generate electricity for general consumption.

As mentioned on the Audi website, this would allow load balancing of the grid: when wind and solar are making more electricity than is being consumed, the excess can be diverted to hydrogen production, which can then be stored. That hydrogen could be used to power fuel cells to generate electricity when wind and solar are offline, or to power vehicles.

Storage of excess energy from wind and solar has always been a major criticism of the technologies. And conservatives don't have to worry: these "green" energy production techniques will still piss off environmentalists. Solar and wind farms will kill some birds and displace some endangered species, and large-scale electrolysis will have to use ocean water, which means there will be briny waste that kill some fish.

We will still be the undisputed rulers of the earth, wielding the power of life and death: it'll just be a little more life and a little less death.

Everybody wins!