Akshat Rathi writes: There’s a colorless, odorless, and largely benign gas that humanity just can’t get enough of. We produce 40 trillion kg of carbon dioxide each year, and we’re on track to cross a crucial emissions threshold that will cause global temperature rise to pass the dangerous 2°C limit set by the Paris climate agreement.

But, in hushed tones, climate scientists are already talking about a technology that could pull us back from the brink. It’s called direct-air capture, and it consists of machines that work like a tree does, sucking carbon dioxide (CO2) out from the air, but on steroids—capturing thousands of times more carbon in the same amount of time, and, hopefully, ensuring we don’t suffer climate catastrophe.

There are at least two reasons that, to date, conversations about direct air capture have been muted. First, climate scientists have hoped global carbon emissions would come under control, and we wouldn’t need direct air capture. But most experts believe that ship has sailed. That brings up the second issue: to date, all estimates suggest direct air capture would be exorbitantly expensive to deploy.

For the past decade, a group of entrepreneurs—partly funded by billionaires like Bill Gates of Microsoft, Edgar Bronfman Jr. of Warner Music, and the late Gary Comer of Land’s End—have been working to prove those estimates wrong. Three companies—Switzerland’s Climeworks, Canada’s Carbon Engineering, and the US’s Global Thermostat—are building machines that, at reasonable costs, can capture CO2 directly from the air. (A fourth company, Kilimanjaro Energy, closed shop due to a lack of funding.) [Continue reading…]