Extracting CO2 from the air is one of the best ways to address climate change without preventing billions of people from getting the energy they need. But the trick is what to do with it afterwards.

Common approaches include injecting it deep underground to get rid of it. But if you could use it to make useful stuff, then it would do double duty and make the products zero-carbon since they wouldn’t put extra carbon into the atmosphere. For years, focus has been on making zero-carbon petrol or jet fuel from the extracted carbon using non-fossil fuels to generate the energy needed.

Today, XPRIZE revealed the two winners in this year’s 20-million-dollar prize for a contest developed to create breakthrough carbon technologies that turn emissions into products with a high net value. The winners were CarbonCure of Canada and CarbonBuilt of California. Interestingly, they both demonstrated technologies focused on decarbonizing the concrete industry.

CarbonBuilt developed a technology that reduces the carbon footprint of concrete by more than 50% while reducing raw material costs. During the curing process, CO2 is directly injected into the concrete mixture where it is chemically transformed and permanently stored.

CarbonCure’s technology enables the production of concrete with a reduced water and carbon footprint while increasing the material’s reliability. The CO2 is transformed into a permanently embedded mineral which can then be combined with new concrete mixes. The technology is able to reduce the material costs and increase profitability for producers.

Concrete is a major contributor to global warming as producing it releases a huge amount of carbon dioxide. Yet it’s the most widely used artificial material, second only to water. Renewable energy sources use much concrete per unit energy produced. If they are to increase enough to make a difference in time to help the planet, getting control of the CO2 in concrete production is essential.

A major new facility to pull CO₂ out of the atmosphere has started operating in Iceland, which is a boost to an emerging technology that experts say could eventually play an important role in reducing greenhouse gases.

The plant in southwest Iceland is the biggest of its kind, its builder says. It is able to capture 900 tons of CO₂ every year but it needs heat and electricity to work. It is using energy produced from waste and is built on the roof of a waste incineration plant, and through the burning of rubbish, energy is generated.

Human-sized fans are built into a series of boxes. They take CO2 out of the air, catching it in sponge like filters(过滤器). The filters are blasted with heat freeing the gas, which is then mixed with water and pumped deep into deep underground basalt caves, where over time it turns into dark-gray stone. Pumping CO2 into the ground is just one way to deal with it. The makers are also selling the gas to be used again. The CO2 can be captured just a few 100 miles away. It is pumped through an underground pipe line directly into a greenhouse. Vegetables and plants love CO2 and higher concentrations of the gas within the greenhouse improve the growth of plants.

By 2050, humanity will need to pull nearly a billion metric tons of CO2 from the atmosphere every year through direct air capture technology to achieve carbon neutral(碳中和) goals, according to International Energy Agency recommendations. The plant in Iceland will be able to capture 4,000 metric tons annually—just a small amount of what will be necessary, but one that Clime works, the company that built it, says can grow rapidly as efficiency improves and costs decrease.