On a tributary of the Hudson River, a tugboat powered by ammonia eased away from the shipyard dock and sailed for the first time to show how the maritime industry can slash planet-warming carbon dioxide emissions.

The tugboat used to run on diesel fuel. The New York-based startup company Amogy bought the 67-year-old ship to switch it to cleanly-made ammonia, a new, carbon-free fuel.

They named the tugboat NH3 Kraken, after the chemical formula for ammonia and their method of “cracking” it into hydrogen and nitrogen. Amogy’s system uses ammonia to make hydrogen for a fuel cell, making the tug an electric-powered ship. The International Maritime Organization set a target for international shipping to reach net-zero greenhouse gas emissions by, or close to, 2050.