Zero-carbon shipping fuel could be a new source of pollution

Switching from burning fossil fuels to burning ammonia is a promising way for the shipping industry to reduce carbon dioxide emissions. But if care is not taken, this exchange can also increase harmful nitrogen pollution.

“That’s a major alarm bell,” he says Xin Zhang at the University of Maryland.

The tens of thousands of ships in the oceans are responsible for about 3% of the world’s CO2 emissions, and burn more than that. 300…