The answer to this underpins some of the “unit”-ization and why many argue that book and claim interventions are a robust method of reducing scope 1 and 3 emissions, much like similar market-based systems are recognized to be durable reductions of scope 2 emissions. In the electricity sector, the precedent is that the REC is not defined as a unit of CO2 reduction but rather a verified megawatt hour (MWh) of renewable electricity generated, which is associated with specific environmental attributes.

A REC is a tradeable certificate representing the holder’s legally recognized property right in the environmental attributes associated with the generation of one-megawatt hour of electricity by a renewable resource. Each REC is a unique certificate that may be traded independently from the underlying electricity, and each REC can be retired by or on behalf of its owner in order to claim usage of the renewable generation represented by the REC. Read more, here, in CRS’ “The Legal Basis for Renewable Energy Certificates”. While RECs aren’t a perfect mechanism, they do provide a valuable precedent for other book and claim systems to build from. This physical unit concept is key to book and claim in heavy transport when we are counting our “claimed” transportation alongside other reported data. We generally count utilizing quantity of fuel or quantity of transportation, not tonnes of carbon emissions reduced. There is a reason for this. These are not out-of-value-chain offsets of in-scope emissions. These are operational emissions directly and verifiably reduced somewhere, which can be claimed somewhere else through the acquisition and retirement of low emissions transportation environmental attributes via structured book and claim systems, as if the claimant had consumed the environmental attributes of the booked units themselves.

One area in which heavy transport book and claim systems have the opportunity to improve upon the REC model is in directly and clearly conveying a verified emissions profile or reduction in relation to an established baseline. Maintaining the physical basis of a unit while standardizing and simplifying emissions profile reporting—i.e. showcasing these parallel metrics side-by-side—is a key opportunity to facilitate accurate and simple disclosure.