International units
Last updated 2 November 2025
International emissions units are used to measure and trade reductions in greenhouse gas emissions on a global scale.
Under the Clean Development Mechanism, emission reduction projects in industrialised countries can earn CERs. Each CER represents one tonne of carbon dioxide-equivalent (tCO₂-e) emissions abated or sequestered.
Each CER has a unique serial number that identifies the:
● unit as a CER
● Kyoto party that issued it
● Kyoto commitment period it was issued for
● CDM project number of the CER.
CERs are only valid for the commitment period for which they are issued.
Individuals, companies or organisations can buy CERs through:
● BidCarbon marketplace
● United Nations Carbon Offset Platform.
Certified emission reduction units (CERs)
Learn more
Voluntary offsetting
BidCarbon removal units are used to measure and trade greenhouse gas emissions globally. Learn more about purchasing and cancel BidCarbon removal units, when you aren't legally required to do so.
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