It turns out there is a way to make cement by absorbing CO2 instead of emitting it.
The technique has been developed by McGill graduates who are semifinalists in the Carbon XPRIZE competition.
The global competition is designed to encourage innovative technologies that convert carbon-dioxide emissions into environmentally sound products.
The McGill group - Mehrdad Mahoutian, Chris Stern, Yuri Mytko and Mario Venditti - call their Montreal-based company Carbicrete.
Cement is a key component in the production of concrete blocks used in construction.
The technology developed by the McGill team substitutes slag from steel factories for cement as the binding ingredient in concrete blocks.
Carbicrete points out their product has environmental benefits and is cheaper to produce.
The competition lasts four years.
Teams advancing to the next round will be evaluated on the amount of carbon-dioxide they convert and the environmental utility of their product.
Carbicrete is into the second round of the $20 million California-based competition along with 26 other teams.
Round two judging is schedued for November and December 2017.