What’s the difference—and which one do I need for what?
As of February 2025
Anyone buying or selling in the biomethane market will encounter two terms that sound similar at first glance but mean fundamentally different things: sustainability certificate (NNW) and certificate of origin (HKN). Both certify something about a quantity of gas—but each certifies something different. This article explains what these two types of certificates entail, how they differ from one another, and when to use which one.
The sustainability certificate verifies that a given quantity of biomethane meets the EU’s legally mandated sustainability criteria. Essentially, it comes down to two questions:
Only when these criteria are verifiably met may the gas be legally classified as “sustainable.” Without a valid sustainability certificate, biomethane does not count as renewable energy for regulatory purposes—regardless of how it was actually produced.
The NNW is the key to accessing government incentive programs and meeting statutory compliance requirements:
In short: Anyone who wants to market or use biomethane for regulatory purposes needs an NNW.
Nabisy is the central registry in Germany when it comes to sustainability in the biofuel sector. For many market participants, it is crucial primarily for one reason:
Distributors of biogenic fuels (e.g., bio-CNG/bio-LNG) can generate GHG quotas and participate in quota trading. This requires that the necessary documentation be correctly maintained in the system.
Nabisy serves as a platform for managing sustainability certificates, transferring them along the supply chain, and invalidating them as needed.
To use Nabisy, you first need an account. This must be requested from the BLE. For traders/suppliers (Lfr) and producers (SSt), certification under a voluntary system is mandatory. Once the account is set up, it can be used to generate (SSt), accept, share, or invalidate certificates (Lfr).
Important: Without a functioning Nabisy setup, marketing through quota-relevant applications can quickly be blocked—even if the biomethane is technically flawless.
Anyone wishing to issue sustainability certificates must be certified by an EU-recognized certification system (e.g., ISCC EU or REDcert EU) and register as an economic operator in Nabisy. Only after a successful audit and active certification can NNWs be generated and transferred in the system. The recipient—whether a trader or end user—must also be registered in Nabisy to receive and process certificates.
The Certificate of Origin does not certify sustainability characteristics, but rather the nature of a quantity of gas: Where does the gas come from, how was it produced, and what are its characteristics?
Typical information included in a certificate of origin includes:
The HKN is therefore a certificate of origin. Put simply, it confirms:
“This amount of energy comes from a renewable source.”
The HKN is primarily relevant in the voluntary and private sectors:
Important: The HKN alone generally does not qualify as fulfillment of statutory sustainability obligations. It supplements the NNW but does not replace it.
In the German market, the dena Biogas Register operated by the German Energy Agency (dena) plays a central role in managing certificates of origin. It documents in detail the characteristics of biomethane—from raw materials and plant technology to greenhouse gas emissions. For every volume of gas fed into the grid, a quality certificate is issued that can be passed along the supply chain.
The registry deliberately goes beyond the minimum legal requirements: It enables granular quality differentiation, which is particularly valuable for premium products and sophisticated purchase agreements.
To issue certificates of origin in the dena Biogas Register, plant operators must register as participants and have their plant data verified by an independent auditor. The recorded quality characteristics are documented and approved on a batch-by-batch basis. Recipients—that is, traders, utilities, or industrial buyers—must also be registered in the dena Biogas Register in order to receive, transfer, or invalidate certificates.
The following table summarizes the key differences:
|
|
Sustainability Certificate (NNW) |
Proof of Origin (HKN) |
|
What is certified? |
Compliance with statutory sustainability criteria + GHG savings |
Characteristics and origin of the gas volume |
|
Nature |
Regulatory / statutory |
Private sector / voluntary |
|
Mandatory or voluntary? |
Mandatory for regulatory crediting |
Voluntary (market-driven) |
|
Who needs it? |
Anyone who uses biomethane for quotas, tax breaks, or similar purposes |
Utilities, industry, entities subject to reporting requirements |
|
German Registry |
Nabisy (BLE) |
dena Biogas Registry |
|
Does one replace the other? |
No |
No |
In practice, the type of certification required—or whether both are needed—depends on the intended use:
If biomethane is used exclusively to meet legal obligations—e.g., for the GHG quota in the transportation sector or for tax relief—proof of sustainability is generally sufficient.
If an energy provider wants to offer its customers a “green gas” product, or if an industrial company wants to document the source of its energy in its sustainability reporting, a certificate of origin is sufficient.
In many commercial transactions, both NNW and HKN are transferred together. This allows the customer to account for the gas both for regulatory and sustainability purposes, as well as to transparently communicate its characteristics. This combination is particularly common among industrial customers with stringent reporting requirements, or when the final use of the gas has not yet been determined.
The UDB (Union Database) is the European system for collecting sustainability and supply chain data. It is gaining importance because it is intended to standardize documentation across the EU and will be made mandatory for all market participants.
For producers and retailers, this means that in addition to national systems such as Nabisy, the UDB will also become relevant in the future.
The UDB is a central online platform operated by the European Commission (DG ENER). Economic operators can access the system in three ways: directly via the web interface, through a third-party service provider authorized by their certification system (Voluntary Scheme), or via their own IT connection using the eDelivery interface.
Organizational management is structured in three tiers: The European Commission operates and hosts the platform. Voluntary certification schemes (VS) handle the onboarding of economic operators, register their certificates, and serve as the central point of contact. Member States are responsible for integrating the gaseous value chain—in particular, DSOs, TSOs, and gas suppliers.
The UDB is intended for all economic operators along the supply chain for renewable and recycled fuels: raw material collectors, producers, processors, traders, and suppliers. Certified operators in the liquid supply chain gain access through their respective voluntary scheme. Non-certified suppliers in the liquid value chain currently do not have access. In the gaseous value chain, DSOs/TSOs, suppliers, and large consumers are connected through the relevant Member States.
Sustainability certificates and guarantees of origin are two different tools serving different purposes. The NNW opens the door to regulated markets and statutory crediting opportunities. The HKN provides transparency regarding the composition of biomethane and is indispensable for credible green product offerings and robust sustainability reporting.
Anyone active in the biomethane market should have a clear understanding of which certification is required for which use case—and how the German registries Nabisy and the dena Biogas Register interrelate in this context.
Would you like to know which certifications are relevant for your specific business model? agriportance would be happy to advise you.