A CER is a certificate which is issued every time the United Nations prevents one tonne of CO2 equivalent being emitted through carbon projects registered with the Clean Development Mechanism (CDM). CDM Projects include for example replacing coal or fossil fuel fired electricity with clean technology, or methane capture from landfill sites.
One Certified Emission Reduction (CER) equates to an emission reduction of one tonne of CO2 equivalent. Holders of CERs are entitled to use them to offset their own carbon emissions as one way of achieving their Kyoto or European Union emission reduction target, or resell them on the market at the prevailing rate.
CERs have emerged as a strong carbon currency accepted in most existing and emerging national and regional emissions trading schemes.
CER prices are increasingly important in the EU and global carbon markets. CERs can be substituted for European Union Allowances (EUAs) by European emitters to meet obligations under the EU ETS.