In an ambitious proposal to counter global warming, an upstart power developer wants to build a coal-fired electric plant on the outskirts of New York City that would capture its emissions of carbon dioxide and pump the pollutant 70 miles offshore. The gas would be injected into sandstone a mile beneath the ocean floor in the hope that it would stay there for eons.

Experts have thought for years that capturing the emissions from power plants will be a crucial technology for limiting climate change. But high cost projections and scientific uncertainty have meant that progress on the technique has been limited, even as the effects of global warming are starting to be felt around the world.

Now SCS Energy, based in Concord, Mass., contends not only that it can build the world’s first such plant and get it to work, but also do so profitably, despite costs that could approach $5 billion. If it succeeded, the plant might become a model that could be copied elsewhere.

A key to the proposal is location: an old industrial site near the shore in Linden, N.J., just across the Arthur Kill waterway from Staten Island. Generating power there would allow the company to sell it into one of the country’s most expensive markets, and injecting the gas deep beneath the ocean floor, where pressure would help keep it down, would eliminate some of the uncertainty that might attend a similar project on land.