Book and claim applies an approach already used in markets such as renewable electricity and sustainable aviation fuel: the physical product and its environmental benefit do not have to travel to the same customer.
Under RMI’s proposed system, qualifying production of low-emissions iron or steel generates an environmental attribute certificate. Once registered, the certificate becomes a book-and-claim unit, or BCU, corresponding to one metric ton of verified iron or steel.
The physical steel can continue through existing distribution channels. The BCU, meanwhile, can be purchased separately by a company seeking to support lower-emissions steelmaking.
Take a U.S. business whose steel arrives through fabricators, distributors or equipment suppliers. A European steelmaker may be producing substantially lower-emissions material, but restructuring the buyer’s entire supply chain to source from that facility could be commercially or logistically unrealistic.
Book and claim creates another route. The U.S. company could purchase and retire the environmental attributes generated by the European facility while the physical steel is sold elsewhere.
That distinction matters for corporate claims. Buying the certificate would not mean that a specific building, vehicle, turbine or other product was physically manufactured from the corresponding low-emissions steel. RMI’s framework is intended to keep the contractual environmental claim separate from claims about the material actually contained in a product.
RMI is also attempting to prevent the system from rewarding minor emissions reductions as though they represented deep decarbonization.
Eligibility is linked to emissions-intensity thresholds, with separate pathways for iron and crude steel. The methodology accounts for scrap content when setting steel thresholds and includes a Near-Zero Aligned designation for qualifying production at the lowest emissions levels.
The framework also sets conditions around production routes involving technologies such as fossil-fuel-based direct-reduced iron, carbon capture and biomass. The goal is to distinguish between different decarbonization pathways rather than treating every reduction in emissions intensity as interchangeable.
For producers, the commercial logic is significant. Hydrogen-based direct-reduced iron, electrification and other low-emissions production routes can require substantial capital investment before a large physical market exists for the resulting steel.
Book and claim potentially expands that market. Producers would no longer depend exclusively on customers able and willing to take delivery from a particular facility. Buyers in other markets could contribute financially to the emissions improvement.
The approach could be particularly relevant for companies that influence steel demand without directly purchasing large volumes from mills.
Automakers can often engage directly with steel producers, while building owners, technology companies, renewable energy developers and other businesses may encounter steel primarily through construction contractors, machinery or manufactured components.
That leaves them with limited leverage over the original producer despite carrying steel-related emissions in their value chains. A book-and-claim system could allow those companies to aggregate demand across projects and geographies without first rebuilding established procurement networks.
In that sense, certificates are less about replacing physical procurement of lower-emissions steel and more about addressing a market-development gap. Early projects need customers prepared to pay a premium for reduced emissions. Requiring every one of those customers to physically receive the associated steel can sharply limit the available pool of capital.
The feature that gives book and claim its flexibility also creates its biggest challenge.
Once an environmental attribute is separated from the physical steel, companies need a reliable way to establish who owns the benefit, who has already claimed it and whether it has been counted elsewhere.
RMI’s framework calls for safeguards including third-party verification, certificate issuance after production, unique registry records and retirement of certificates before environmental claims are made. It also seeks to prevent the same attribute from being issued or claimed more than once.
Vintage requirements are another control. These are intended to reduce the risk that companies accumulate old environmental attributes and later apply them to reporting periods disconnected from the production that generated the emissions reduction.
Product-level reporting could prove more complicated.
One concern identified in the framework is that an emissions factor adjusted using book-and-claim certificates could move downstream through an environmental product declaration or product carbon footprint and then be reused by organizations that never purchased the underlying certificate.
For example, an environmental benefit associated with 10,000 tons of steel could effectively spread across a much larger volume if an adjusted emissions factor entered product documentation or lifecycle databases without sufficient controls.
That creates a potential disconnect between what the registry records and how downstream companies report emissions.
RMI’s approach therefore emphasizes keeping book-and-claim accounting distinct from emissions information associated with physically purchased steel. For corporate buyers, that distinction is likely to be critical for assurance teams, investors and customers evaluating climate disclosures.
Another source of uncertainty sits outside the steel market itself: corporate greenhouse gas accounting rules are still developing.
RMI’s framework provides guidance for early transactions rather than functioning as a finalized certification standard or operating registry. At the same time, the GHG Protocol is developing an Actions and Market Instruments Standard addressing instruments that include green-steel certificates.
Its current work is still evolving, meaning businesses considering steel certificates need to evaluate more than the technical quality of the underlying project.
They will also need to determine how any resulting environmental claim interacts with Scope 3 inventories, corporate climate targets, reporting requirements and external assurance.
That is likely to be the real test for the model.
Book and claim could give steelmakers access to a broader pool of climate-focused capital while allowing companies with complicated supply chains to support lower-emissions production. But its long-term value will depend on whether the market can maintain credible emissions baselines, independent verification, clear ownership of environmental attributes and strict controls against double counting.
The physical steel may travel one way and its environmental attribute another. For the model to scale, the accounting around both will need to remain clear.
