Pulling carbon dioxide (CO2) from the air and using it to make synthetic fuel seems like the ultimate solution to climate change: Instead of adding ever more CO2 to the air from fossil fuels, we can simply recycle the same CO2 molecules over and over. But such technology is expensive—about $600 per ton of CO2, by one recent estimate. Now, in a new study, scientists say future chemical plants could drop that cost below $100 per ton—which could make synthetic fuels a reality in places such as California that incentivize low-carbon fuels.