The main goal of the voluntary carbon market is to drive finance to carbon projects that reduce greenhouse gas (GHG) emissions. Carbon offsets are the vehicle that connects carbon projects with consumers that purchase offsets to achieve their climate targets. A carbon offset represents a measurable and verifiable removal, reduction, or avoidance of GHG emissions and is denominated in tCO2e (which means "tonne of CO2 equivalent").
→ Take a deeper dive into carbon offsets with these docs.
→ Learn about how voluntary carbon markets differ from compliance markets here.
In the voluntary carbon market, carbon standards set the rules and requirements carbon projects need to follow in order to demonstrate they meet minimum quality criteria. Verra's Verified Carbon Standard and Gold Standard are the two major players, with smaller standards issuing less than a quarter of total offsets each year.
The "rules" carbon projects need to follow are a combination of high-level requirements and processes set by the standard and specific accounting methodologies. A methodology dictates things like monitoring requirements and is different for each carbon offset-generating activity. A methodology for protecting forests from deforestation requires different data to be collected than a methodology for wetland restoration. Independent 3rd parties—a list of auditors authorized by each standard—will assess projects against these rules and requirements. Only after a successful verification will the project be issued offsets by the standard body.
Each standard maintains a centralized registry with a list of all its projects, and the issued and retired offsets associated with each project.
After projects have proven that they've removed or reduced GHG emissions they are issued offset credits that are in an active state. Because projects generally don't have direct contact with companies who will buy their offsets to satisfy sustainability claims, they often sell them to intermediaries—brokers, resellers, and retailers. Offset credits can pass from one hand to another without changing their status. But when an end-buyer wants to use the offsets to compensate their GHG emissions for carbon accounting purposes, the offsets need to be retired. Now the offset has fulfilled its "duty" and nobody else will be able to claim the carbon removal or reduction for their books. A registry account is needed to trade carbon credits in an active state. These accounts can cost $1000 a year in the case of Gold Standard.