As European energy markets strive to achieve a minimum 55 per cent cut in greenhouse gas emissions by 2030, biomethane has emerged as a strategic tool for decarbonising high-emission sectors. Upgraded from raw biogas to a methane purity exceeding 95 per cent, biomethane shares the same energy density and physical quality as fossil natural gas, making it a drop-in replacement that can be injected directly into existing gas grids. However, as the market matures, corporate buyers and fuel suppliers face a highly complex, bifurcated regulatory landscape. Navigating the biomethane market now requires a clear understanding of the fundamental distinction between Proof of Sustainability certificates, which are bound to physical mass balance systems, and gaseous Guarantees of Origin, which operate on a book-and-claim basis.

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The Rigour of Mass Balance: Proof of Sustainability

For organisations seeking to use biomethane for official regulatory compliance, the primary instrument of choice is the Proof of Sustainability, or PoS. Under Article 27 of the second Renewable Energy Directive, a principle fully maintained under RED III, any renewable gas claimed toward European decarbonisation targets must be verified using a strict mass balance chain-of-custody system.

A mass balance framework requires physical linkage to the gas network. Under this system, while the physical green molecules do not need to be delivered to the exact point of consumption, the supplier must demonstrate that an equivalent volume of biomethane was physically injected into the interconnected grid. A PoS certificate contains highly granular data, including the specific feedstock used, the exact production pathway, and the verified greenhouse gas emission factor. These certificates are issued by economic operators under voluntary schemes approved by the European Commission, such as ISCC or REDcert.

Because of this rigorous physical tracing, PoS certificates are the only instruments accepted for formal compliance obligations. Sourcing a physical PoS is mandatory for companies attempting to offset emissions under the European Union Emissions Trading System, satisfy fuel targets under the FuelEU Maritime regulation, or meet the strict transport fuel quotas set out in national legislations.

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The Flexibility of Book-and-Claim: Gaseous Guarantees of Origin

In contrast to the physical constraints of the PoS, gaseous Guarantees of Origin, or gGOs, provide a more flexible mechanism designed primarily for consumer disclosure and voluntary green claims. A gGO is defined as an official document certifying that a specific unit of gas was produced from renewable sources, including renewable hydrogen.

Unlike a PoS, gGOs operate under a book-and-claim model. Under this system, the environmental attributes of the renewable gas are decoupled from the physical commodity. This decoupling allows the certificates to be traded, exported, and imported across European member states completely independently of the physical gas flow. A corporate buyer located in a region with limited local biogas production can purchase gGOs from a producer in another European country to back up their green marketing campaigns or voluntary corporate sustainability reports.

This separation of attributes is highly valuable for market liquidity, but it introduces strict safeguards to prevent double counting. If both a PoS and a gGO are issued for the same batch of biomethane, the regulations dictate that they must remain strictly bundled. This bundling ensures that a single unit of renewable gas cannot have its physical compliance value claimed by an industrial facility under the EU ETS while its green marketing attributes are sold to a separate corporate client.

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Structuring National Registries: The Irish Supervisory Framework

As the trans-European biomethane trade expands, national regulatory bodies are establishing formal registry frameworks to bring structure and credibility to the gGO market. A prominent example of this regulatory maturation is Ireland's Commission for Regulation of Utilities, or CRU, which published its definitive decision paper on a supervisory framework for renewable gas guarantees of origin on 24 March 2026.

The Irish framework provides a clear operational model for registry integration and trade rules. The CRU appointed Gas Networks Ireland, the national gas network operator, as the official Issuing Body for gGOs. Under this framework, producers, traders, and suppliers can hold active accounts in a centralised electronic registry. However, to preserve market integrity, the framework restricts administrative actions: while any account holder can transfer certificates, only producers can request the issuance of gGOs, and only suppliers are permitted to execute final cancellations.

Furthermore, the Irish framework integrates strict sustainability requirements directly into the issuance process. A gGO will only be issued on a monthly basis after Gas Networks Ireland verifies the producer's sustainability credentials through European voluntary certification schemes. This rigorous approach is also applied to imported certificates, which must meet equivalent European sustainability criteria once the Internal Gas Market Directive is fully transposed into Irish law. To fund this oversight, the registry imposes annual fees of 2,000 euros for producers and 3,000 euros for suppliers and traders. Reflecting the strict connection to physical infrastructure, the Irish framework is restricted exclusively to grid-injected gas and prohibits trading with the United Kingdom, in accordance with the current lack of a bilateral legal agreement between the UK and the EU.

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Strategic Implications for Corporate Procurement

For corporate energy buyers, the bifurcation between PoS and gGO certificates has immediate strategic consequences for contract design. Relying solely on a gGO is insufficient for organisations that must satisfy mandatory carbon compliance or legally binding greenhouse gas reduction quotas. Without a physical PoS and a verified mass-balance chain of custody, auditors and regulators will reject claims of zero-carbon gas use.

Conversely, for voluntary corporate disclosures under frameworks such as the Corporate Sustainability Reporting Directive, or CSRD, gGOs provide a verified and auditable method to demonstrate support for renewable energy. When negotiating long-term Biomethane Purchase Agreements, procurement teams must ensure that contracts explicitly define who owns both the PoS and the associated gGO. By structuring these agreements with professional advisory support, businesses can successfully navigate this bifurcated market, securing the exact environmental attributes needed to satisfy both their voluntary sustainability goals and their mandatory regulatory obligations.