In the not so distant future, when you fill up your car, you may be pumping gasoline made from air instead of fossil fuels. The technology to make this happen already exists.

In the U.S., transportation accounts for nearly one-third of all greenhouse gas emissions. While driving generates a number of harmful pollutants, including carbon monoxide, sulfur dioxide, and nitrogen oxide, the most dangerous with regards to climate change is carbon dioxide: Burning through one gallon of fossil fuel-derived gasoline spits 19.6 pounds of carbon dioxide into the atmosphere, where it acts as a heat-trapping gas and contributes to a warming planet.

As concerns about climate change and pollution increase — and America's love for driving remains as strong as ever — the search for alternative fuels is intensifying. This is where something called carbon-neutral fuel comes in. These fuels promise no net greenhouse gas emissions and a carbon footprint of zero. This means that the amount of carbon dioxide emitted by burning the fuel is balanced by the amount removed from the atmosphere to create it. All carbon-neutral fuels function the same way: They neither add to nor decrease the amount of carbon dioxide in the air.

A company called Carbon Engineering wants to create a carbon-neutral fuel by capturing carbon dioxide from the air and turn it into synthetic gasoline. The company's process, called Air to Fuels (A2F), is deceptively simple on the surface: It extracts carbon dioxide from the air, puts it through chemical processes, and creates liquid hydrocarbon fuel. (Hydrocarbons are organic compounds consisting only of hydrogen and carbon. Oil and gasoline are examples of liquid hydrocarbon fuels. The A2F process creates a synthetic version of a liquid hydrocarbon fuel.)

But perhaps unsurprisingly, in reality, it's a bit more complex. Carbon Engineering uses something called direct air capture (DAC) technology to extract the carbon dioxide from the atmosphere and purify it. Then, it relies on a renewable energy source, such as solar power, to make hydrogen by electrolyzing water (H2O). The hydrogen splits off from the water and is free to combine with carbon dioxide. Next, the process combines the carbon dioxide with hydrogen during a proprietary chemical process, and carbon-neutral liquid fuels like gasoline, jet fuel, or diesel are born.

The good news is that you don't have to modify your current car engine for this synthetic gasoline to work. So if your '90s Toyota or Chevy is still going strong, you won't be forced to get rid of it.

But there's one big problem with Carbon Engineering's alternative fuel: the cost. In a peer-reviewed article published in Joule, the company shared that the process currently costs between $94 and $232 per ton of carbon dioxide, as opposed to the traditional process of extracting fossil fuels, which costs about $20 per barrel in the U.S. Some estimates show that synthetic gasoline could cost between $3.80 and $9.20 a gallon. That's likely to be more than the average driver is able or willing to afford.

Carbon Engineering knows this is a problem.

"A2F [Air to Fuels] is the future because it needs 100 times less land and water than biofuels, and can be scaled up and sited anywhere," Geoff Holmes, director of business development at Carbon Engineering, told The Guardian. "But for it to work, it will have to reduce costs to little more than it costs to extract oil today, and — even trickier — persuade countries to set a global carbon price."

The company claims it could produce synthetic fuel for about $1 per liter, or $3.78 per gallon, once production scales up. It also says it's also working on lowering costs by using readily available industrial processes and technology rather than reinventing the wheel. Next, it plans to build full-scale commercial facilities and, hopefully, have customers who are eager to buy its product.

"We imagine individual facilities going to megaton scales — million tons of CO2 captured per year at individual facilities," Holmes told The Daily Beast. "That's capturing and purifying the quantity of emissions released by 250,000 cars […] If you ask yourself, which is more difficult, reducing 250,000 cars or building a facility? It's probably harder to reduce 250,000 cars."

Critics have pointed out that Carbon Engineering's process puts carbon dioxide right back into the air when cars burn the synthetic gasoline. So Air to Fuels can temporarily remove carbon dioxide from the atmosphere, but it won't permanently reduce it. Carbon Engineering acknowledged this when its founder David Keith told National Geographic: "This isn't going to save the world from the impacts of climate change, but it's going to be a big step on the path to a low-carbon economy."