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

Switching from fossil fuel to burning ammonia is a promising way to cut carbon dioxide emissions for the shipping industry. But if it is not careful, this swap can also promote harmful nitrogen pollution.

“This is a major alarm bell that is ringing,” says Shin Zhang At the Maryland Center for Environmental Sciences.

Thousands of ships on the oceans are responsible for about 3 percent of global CO2 emissions,…