An emitter is something that releases or gives out something, such as light, sound, or particles. It is like a source that sends out or emits energy or information. Full definition
One report concluded that China's total energy use now tops that of the United States, just a couple of years behind its rise to the top position on lists of emitters of carbon dioxide. (dotearth.blogs.nytimes.com)
Overwhelming disapproval was launched at the second largest emitter of greenhouse gases, with claims that it was acting fecklessly rejecting what many nations see as necessary progression towards a greener planet. (blog.politics.ox.ac.uk)
If food waste was a country it would be the third biggest emitter of greenhouse gases globally after China and the US. (sustainablebrands.com)