Selling “carbon credits” is an effort to reduce greenhouse gas emissions by giving them a monetary value.

In theory, this is how it works: One credit gives the owner the right to emit one ton of carbon dioxide into the atmosphere.

International treaties, such as the Kyoto Protocol, set quotas on the amount of greenhouse gases countries can produce. Countries, in turn, set quotas on the emissions of businesses. Businesses that emit over their quotas must buy carbon credits for their excess pollution, while businesses that emit below their quotas can sell their remaining credits. By allowing credits to be bought and sold, a business for which reducing its emissions would be expensive or prohibitive can pay another business to make the reduction for it. This minimizes the quota's impact on the business, while still reaching a country’s quota.

Credits can be exchanged between businesses or bought and sold in international markets at a prevailing market price. Currently, two exchanges for carbon credits are chartered, the Chicago Climate Exchange and the European Climate Exchange. Lobster.COM joined the Chicago Climate Exchange (CCX).