By Katherine Bourzac
Scientists are trying to convert carbon dioxide emissions into something of value—without using too much energy
We humans emitted 35.9 metric gigatons of carbon dioxide into the atmosphere in 2014, mostly from burning coal and natural gas in power plants, making fertilizer and cement, and other industrial processes. If chemists could capture carbon dioxide and turn it into chemical building blocks for other products, the way plants do, says Cornell University chemical engineer Lynden Archer, “carbon dioxide would not be a nuisance anymore, but a gift.”
For years scientists have been trying to store carbon dioxide captured from exhaust flues at power plants and other emitters, mostly by injecting it deep underground. Without large subsidies, however, this expensive carbon sequestration process may not be economically viable. Injecting carbon dioxide into old oil wells to drive out more oil is one application, but it’s not enough, and it’s not clear it even pays, given current low oil prices. Proponents of utilizing carbon rather than storing it hope they will profit by creating something of value from this waste product. The most likely applications use the gas as a raw material for making chemical products, which could also pay off by replacing petrochemicals with something greener.
These proponents face a difficult chemistry problem. Carbon dioxide is a stable molecule, and doesn’t store much energy in its chemical bonds. To use it, chemists have to add energy, often through heating, which usually requires electricity. Much of that comes from power plants that burn coal or natural gas—emitting more carbon dioxide into the atmosphere, even more than was captured.
Engineers, chemists and other researchers say new technologies are changing the picture. Paul Bunje, senior scientist in the Energy and Environment group at the XPrize Foundation, hopes that awarding a big prize for a solution will stimulate a diverse group of technologists. Next Wednesday, the foundation will announce that more than 40 teams are competing to win a $20 million prize. The winner of the Carbon XPrize, to be announced in spring 2020, will sequester the most carbon dioxide into a product of greatest net value. Some teams aim to make polymers, or fuels to replace gasoline, or industrial chemicals.
In the longer term, all the different companies producing one chemical or another could make up a carbon-utilization industry that could make a difference. A problem on the scale of climate change needs multiple solutions, Bunje says.