Book and claim lets a buyer pay for low-carbon fuel and steel it cannot physically receive

Book and claim is a chain-of-custody model in which the environmental attribute of a product, such as the lower emissions of a fuel, is traded separately from the physical product. The producer or user of the low-carbon product books the attribute in a registry. A buyer elsewhere in the same system buys it and claims it, and the registry records that the attribute has been used once.

It exists because physical delivery is often impossible. Fuel goes into shared bunkering, pipeline or airport systems, and steel from one plant is mixed with steel from others before it reaches a car maker. Without book and claim, a company that wants to pay for a lower-emission version of a product it buys has no way to do so unless the product happens to reach it.

Maritime. A carrier burns a lower-emission fuel on one vessel, and cargo owners whose goods travel on other vessels in the same network buy certificates for the emissions benefit. The Mærsk Mc-Kinney Møller Center for Zero Carbon Shipping has published a maritime book and claim methodology, and the Book and Claim Community, founded by the Smart Freight Centre and RMI, has published principles and best practices for book and claim in heavy transport.

Aviation. Sustainable aviation fuel (SAF) is supplied into airport fuel systems, so the airline or corporate buyer rarely receives the molecules it paid for. Registries such as the RSB Book and Claim Registry and the SAFc Registry record SAF certificates. The Sustainable Aviation Buyers Alliance publishes a list of registries it considers eligible. Corporate buyers typically relate SAF claims to Scope 3 Category 6, business travel, or Category 4 for air freight.

Steel. RMI published a Book and Claim Framework for the Iron and Steel Sector in February 2026. It sets out how certificates for low-emissions steel could be issued against verified emissions performance, transferred, retired and tracked in a registry. It is guidance for pilots, not yet an operating certification scheme. For imported steel, the EU’s border carbon price adds a separate data requirement; see CBAM and Scope 3.

• A defined system boundary in geography and time, so the attribute is claimed within a system the buyer draws on.
• Independent verification of the emissions benefit at the source, against a stated baseline or reference fuel.
• A registry that gives each certificate one identifier and one holder, records every transfer and retires it permanently, so no tonne or tonne of fuel is claimed twice.
• Clear rules on which claims a certificate supports, and disclosure of whether it is reported within the inventory or separately.