This idea, favored by many economists, is similar to a system that already allows electric utilities to trade air-pollution credits.
European countries that consume oil refined from African countries have the opportunity to subsidize the costs of individual level, village level, or community level alternative energy systems through emissions trading credits.
The Clean Air Act allows generators of acid rain gases to trade credits, allowing the emission of a certain amount of pollutants.
The remaining 30 percent was converted to trade credits, repayable at low rates of interest over a period of up to 20 years.
And under proposals to cap emissions nationally and let companies trade credits for extra reductions, only the cheapest methods of reducing greenhouse gases would thrive in the marketplace.
In January, the Bush administration proposed allowing coal-fired electric power plants, the primary sources of mercury pollution, to trade credits for mercury emissions.
The strategy would set tighter limits of national emissions of major pollutants but allow utilities to trade credits among themselves, in effect, letting the market dictate how the limits are met.
For utilities and manufacturers, the ability to trade credits could take some of the sting out of regulation.
Last spring, hard-strapped Bulgaria had to stop all payments on that debt, and as a result it has no access to trade credits or foreign capital.