If global warming is a problem, and if it can be restrained by reducing emissions of greenhouse gases, then Georgists suggest a tax on emissions would be the way to go. Proceeds of this tax can be used to reduce taxes on productive activity, benefitting everyone who works.
The alternative “cap and trade” approach gives existing polluters a tradeable right to pollute, tho not quite so much as they have been doing. These emitters can either clean up their operations, or buy credits from others who have reduced net emissions.
And that’s where the problem comes up, how do you measure emissions which didn’t occur? Today’s WSJ describes how some landfill operators can get credit for capturing methane emissions from their facilities. The fact that they might already be harvesting the methane and selling it is irrelevant, so WSJ considers that a “double-dip.” The article notes that not all landfills are eligible, only those small enough that they aren’t legally required to capture methane.
Describing the experience of one Pennsylvania landfill operator, WSJ notes “its first carbon-credit sale, netting $26,600 after paying $11,900 in fees and commissions…” 31% of the revenue goes to the traders. There’s the free market in action.