Think, for a moment, of carbon dioxide as garbage, a waste product from burning fossil fuels. Like other garbage, almost all of that CO2 is thrown away — into the atmosphere, where it contributes to climate change. A small amount is captured and stored underground to keep it out of the air.

But increasingly, scientists are asking, rather than throwing away or storing CO2, how about recycling some of it?

At laboratories around the world, researchers are working on ways to do just that. The X Prize Foundation has created an incentive, a $20 million prize for teams that by 2020 come up with technologies to turn CO2 captured from smokestacks of coal- or gas-fired power plants into useful products.