Climate change is already significantly impacting California’s water system—and those effects will only worsen in the coming years. Reducing greenhouse gas emissions is essential, and California is set to play a major role in those efforts. In November, the nation’s first direct air capture (DAC) facility opened in Tracy, California. But what is direct air capture, and how does it fit into the state’s emissions reduction strategy? We turned to Roger Aines, who leads the Carbon Initiative at Lawrence Livermore National Labs, to tell us more.

What is direct air capture and how does it work?

There’s too much carbon dioxide in the atmosphere. We need to stop putting carbon dioxide into the atmosphere, but that alone won’t fix the fact that there’s already too much there. We’ve developed technologies to remove some of that carbon dioxide, and the simplest of those is called “direct air capture.”

A machine sucks in air, removes the carbon dioxide, and spits clean air back out. Perhaps the most challenging thing is finding permanent storage for the CO2. Almost always, the answer is to put it back where it came from: deep underground in rocks that held oil for millions of years. When you put carbon dioxide deep underground, it turns into a liquid that’s very similar to oil. The Department of Energy (DOE) has worked on this for a long time, and they’ve put 14 million tons of CO2 underground in experimental programs. We’re confident that we can do it safely.

Tell us about its profile nationally and in California.

There are only four machines that capture carbon dioxide from the air around the world today, and they’re capturing a thousand tons of CO2 a year—which is nothing. People are working to figure out how to build these machines more cheaply and efficiently. Driving down the cost is important, because the scale of the need is enormous: by 2050, we’ll need a carbon removal industry that’s twice the size of the global oil industry today. (The world currently produces about 5 billion tons of oil a year.) The good news is that these machines work, and they work pretty well.

Would adopting direct air capture mean that we’re giving up on limiting greenhouse gas emissions?

That’s a grave concern. This is an area that begs for policy and regulatory attention.

About 80% of worldwide greenhouse gas emissions can be eliminated by eliminating fossil fuels and becoming more efficient. But we can’t get rid of about 20% of our emissions, which we call “residual emissions.” In California, one of the interesting sources of residual emissions is fertilizer, for instance. We believe that we should only use DAC to erase residual emissions.

How much land will this technology need as it scales up?

That’s the most important constraint on it, by far—the money is nowhere near as hard as the land. We’ll need to be removing between 1.5 and 10 billion tons of carbon from the atmosphere annually by 2050. It takes roughly seven square miles of solar panels to power 1 million tons of DAC capacity. The DAC facility would look like a large apartment complex surrounded by seven square miles of panels.

The DOE asked Lawrence Livermore National Lab to undertake a national-scale analysis of the carbon dioxide removal required to meet the administration’s climate goals in response to this historic challenge. Our new report, “Road to Removal,” describes a panoply of opportunities for DAC across the country. It maps out available land—land that’s not a city, a park, an active farm, protected, or a wetland—and it also maps land with the geology to store CO2. There are a lot of places in the western US—including a strip ranging from Texas to North Dakota and places like California’s Central Valley—where those conditions come together. Bakersfield, for instance, has all the right physical characteristics: there is storage under the old oil fields, copious land, and an experienced oil workforce that can do the job.

What are the challenges and opportunities in scaling up?

We need to scale up an enormous amount, very quickly, and it’s hard to build these facilities quickly. Heirloom’s facility in Tracy took about a year and a half to build. We consider removing 1 million tons of carbon annually to be an efficient size for a DAC facility—that’s a thousand times bigger than what they built in Tracy. That’s one reason the government is investing in all these projects. The government is supporting 12 more projects around the country right now.

What gives you hope?

I am fundamentally as optimistic as anybody in this field—I see so many ways to succeed. One way is to take CO2 out of the air, but that’s one of the most expensive and difficult methods. There are many other things we can do today, including taking better care of our forests and soil so they can capture and store more carbon, keeping carbon in our trash from returning to the air, turning agricultural waste into hydrogen and CO2, and working with the oceans to reduce CO2. A bunch of methods may fail, but many will succeed.