Dozens of companies and academic groups are pitching the same theory: that sinking rocks, nutrients, crop waste or seaweed in the ocean could lock away climate-warming carbon dioxide for centuries or more.

From the grounds of a gas-fired power plant on the eastern shores of Canada, a little-known company is pumping a slurry of minerals into the ocean in the name of stopping climate change.

Whether it’s pollution or a silver bullet that will save the planet may depend on whom you ask.

From shore, a pipe releases a mixture of water and magnesium oxide — a powdery white mineral used in everything from construction to heartburn pills that Planetary Technologies, based in Nova Scotia, is betting will absorb more planet-warming gases into the sea.

“Restore the climate. Heal the ocean,” reads the motto stamped on a shipping container nearby.