Green money sounds nice-eh? It means both the greenbacks and eco-friendly.
Are you operating a blog on green issues? There is an ad network that is willing to serve your green blog with green oriented banner ads. You can try to monetize your blog with this new kind of advertising.
I believe there are more green ad networks in the Internet and more to come. They offer PPC, CPM and CPA types of advertisement.
Since this a niche advertising segment, you can expect the approval process to be strict. Most of the websites that focus on alternate energy sources, sites that speak for paperless work will be approved easily.