The phrase "net emitter" refers to something or someone that releases or produces more of a certain thing (usually gases or pollutants) than it takes in or absorbs. Full definition
Now, in a perverse twist, a new study shows that in a few years, the pests will have turned the once climate - friendly forests into net emitters of carbon dioxide. (dotearth.blogs.nytimes.com)
Ponds and lakes play a significant role in the global carbon cycle, and are often net emitters of carbon gases to the atmosphere. (sciencedaily.com)
As exciting as these wildlife changes have been, Hey notes that potentially more important is a change in the environment's chemistry — a change that has turned the wetland from a net emitter of nitrates to an eliminator of these pollutants. (sciencenews.org)