The authors, abandoning efforts to have a single economy - wide mechanism for trading pollution credits, have separate sets of carrots and sticks for utilities, transportation and manufacturing. (dotearth.blogs.nytimes.com)
And that's where the idea of pollution credits comes in. (sciencenews.org)
The whole buying pollution credits doesn't solve the «protect the environment» issue. (dotearth.blogs.nytimes.com)