You wouldn't burn the ammonia, but use a process to 'crack' ammonia into hydrogen and nitrogen gas, for example [1]. No oxygen is involved.
Edit: Upon rereading, I found that the article actually states: "There are challenges. Burning ammonia can create polluting nitrous oxides, therefore the exhaust needs cleaning up", which would indicate they're burning it. So either the reporter misunderstood or it's really a non-innovation then.