The evolution of a biomass standard: how Puro.earth has approached biochar feedstock sustainability 

When we published our first Biochar Methodology in 2019, the sector looked very different from how it looks today. The projects we were certifying were smaller, the feedstocks were more straightforward, and the supply chains were shorter. The biomass requirements we wrote then were rigorous and fit for that moment.  

Since then, the sector has grown considerably, and our biomass sourcing requirements have developed alongside it as part of the normal cycle of methodology review and revision. This article sets out the approach we have taken, and why.  

Where we started 

Our very first biochar methodology, published in 2019, took a deliberately narrow approach: forest biomass was only eligible if it came from the EU and from PEFC- or FSC-certified forests. Besides forest biomass, eligible feedstocks were limited to waste biomass such as agricultural waste, biodegradable waste and food waste.  

As Puro.earth began working with a broader and more diverse set of biochar project developers, Edition 2022 of the Biochar Methodology progressively broadened that scope. Version 1 removed the EU-only restriction on forest biomass, and offered several evidence routes reflecting the diversity of contexts in which biochar projects operate. The most commonly used of these has been certification through recognised international schemes such as FSC, SFI or PEFC – well-established frameworks with broad market recognition.  

Version 3 then added a further evidence route: forest management plans approved by a government, state or regional authority, provided the country scores 50 or above on Transparency International’s Corruption Perceptions Index. Version 3 also made explicit that proof of origin and sustainability must be kept in records, submitted to Puro.earth and made available for output audits.  

Throughout Edition 2022, a further route also allowed Puro.earth to assess and approve other reputable certification programmes with high scientific standards and market recognition, whether public or private, on a case-by-case basis, beyond the three pre-approved forest management schemes (FSC, SFI and PEFC). This reflected the fact that other reputable certification schemes exist and that some jurisdictions have robust statutory forestry frameworks, with defined management plans, inspection regimes and enforcement powers. Recognising those frameworks required proper evaluation of what the law requires, how it is enforced and whether it credibly addresses our sustainability criteria. If a framework is established and mandated by law, and that law sets out robust requirements and enforcement mechanisms, that carries genuine weight.  

That approach – embedded in the methodology, applied case by case – worked well for a sector at an earlier stage of development. But as biochar has scaled, and as the range of feedstocks has diversified, it became clear that a more systematic framework was needed. 

Biomass Sourcing Criteria: a natural next step 

The Biomass Sourcing Criteria (BSC) were introduced to create a more uniform way to apply biomass sourcing rules on an increasingly growing number of projects, each bringing their own unique approaches and models.  

First published in May 2024 and consulted on as part of our Geologically Stored Carbon methodology updates, the BSC acts as a layer across all of Puro.earth’s biomass-based methodologies. Each methodology then adds pathway-specific requirements on top: biochar, for example, has strict rules on hazardous biomass and impurity contamination that don’t apply in the same way to other pathways. The two layers work together, but each can evolve independently. That flexibility is important in a sector moving as fast as biochar.  

The practical problem we encountered with an increasingly growing number of projects using our older methodologies was project diversity: numerous projects, in numerous jurisdictions, of different scales and supply-chain complexity, and subject to different forest and biomass regulations.  

Addressing all of that within a single methodology, written primarily around the biochar production process itself, was increasingly unwieldy. Requirements needed to be consistent across methodologies, updatable independently of the production rules, and clear enough to be applied reliably by suppliers and auditors operating across very different contexts. 

The same logic applies across all biomass-based CDR pathways. Bioenergy with carbon capture and storage (BECCS) draws on many of the same feedstock types as biochar – agricultural residues, forestry biomass, dedicated energy crops – and raises the same fundamental questions about origin, sustainability and traceability. As Puro.earth’s portfolio of biomass-based methodologies has grown, the case for a single coherent framework governing the feedstock question across all of them has become stronger. 

How the BSC works 

The BSC recognises 16 distinct feedstock categories – from forest biomass and agricultural residues to food waste, municipal sludge, animal waste, aquatic biomass and conservation landscape management material. Each category carries different socio-ecological risks, and the BSC calibrates its requirements accordingly. For each category, three things are defined: the traceability information that must be documented, the sustainability criteria that must be evidenced, and the evidence options available to demonstrate them. 

For lower-risk waste-derived feedstocks, the requirements are relatively straightforward: demonstrate the material is what it claims to be, comes from where it is said to come from, and has not been deliberately produced for CDR purposes.  

For forest biomass, the bar is substantially higher: legal operations, systematic regeneration, maintenance of carbon stocks and soil quality, protection of water resources and biodiversity, avoidance of primary forests and high-value ecosystems, and respect for the rights of indigenous communities. 

The evidence options are deliberately flexible. A supplier can use an FSC forest management certificate toward meeting our criteria – but the certificate is not itself a pass. It needs to be matched against the specific BSC criteria it addresses, and gaps need to be filled with additional evidence. The same principle applies to national regulatory frameworks: where a statutory forestry scheme is mandated by law and credibly addresses our criteria through its requirements, inspection regime and enforcement powers, it can serve as a legitimate evidence route. What matters is whether the framework actually does what it says – and that requires a real assessment, not an assumption. 

Compliance operates in two steps. At the initial facility audit, the supplier presents a demonstration plan – criterion by criterion, source by source – showing how compliance will be evidenced. This plan is reviewed and validated by the independent auditor. Subsequent output audits then verify that the plan is being executed: that the records are being kept, the evidence is being collected, and the sources remain as declared. The first step is the more intensive one. Once validated, it makes the ongoing audit cycle more focused and efficient. 

Going further 

Suppliers who go further – and publish additional information either on their own websites, their supplier listing or on the Puro Registry – are doing something genuinely valuable for the sector.  

Suppliers can use their facility listing to publish a wide range of additional information, such as traceability documentation, samples of the records that underpin their supply chains, lab reports, information related to Sustainable Development Goals and the project purpose and mission. Where documentation is commercially sensitive or involves complex regulatory records that might only be available to regulators or auditors, suppliers can publish extracts alongside explanatory context – for instance, helping to demonstrate how the traceability system works without compromising confidential information. We think this kind of voluntary transparency reflects well on the sector, and we actively support suppliers who choose to do it. 

The next chapter: BSC v1.3 and Biochar Edition 2025 

The BSC is a living document, updated at least every two years – or sooner when the science or operational experience demands it. Version 1.0 was published in May 2024; v1.1 followed in June 2025 (alongside the Biochar Edition 2025 public methodology consultation); v1.2 in November 2025; v1.3 was published in September 2026.  

Under the BSC, suppliers must declare all biomass sources upfront and maintain batch-level records for every delivery, linking each consignment to a declared source and feedstock category. These changes apply across biochar, BECCS and all other pathways governed by the BSC. 

Biochar Edition 2025 then builds pathway-specific biomass requirements on top of this base. For instance, the methodology tackles four areas of more explicit operational requirement:  

• Suppliers must assess and report impurity levels in their biomass sources, distinguishing between plastics, metals, glass and minerals, and account for their effect on carbon removal calculations in a manner commensurate with the risks. 

• Biomass stockpiling at the facility must follow documented procedures that minimise decomposition, methane emissions and fire risk. 

• Biomass that is hazardous, contaminated with micropollutants or classified as hazardous waste must be declared and managed accordingly, separated from other biomass streams; and resulting biochar use is restricted to specific applications.  

• Co-firing of biomass with fossil coal or fossil oil is explicitly prohibited.  

Further, the durability threshold has been raised from CORC100+ to CORC200+, reflecting the current scientific consensus on biochar carbon stability – and while some in the sector have argued for even longer durability claims, we have deliberately not moved to CORC1000+. Where the science does not yet robustly support a more expansive claim, we take the more conservative position. 

As Puro-certified projects typically have crediting periods that last five years, the first facilities applying the 2025 Biochar Edition and the current BSC are going through audit preparation right now, and we expect the first issuances to take place in the coming months. Assessments of national biomass regulatory frameworks, where these are used as evidence routes, are also revisited within the context and requirements of the BSC.  

Taken together, the BSC and Biochar Edition 2025 represent the most significant strengthening of our biomass sourcing and biochar carbon accounting requirements since we published our first biochar methodology in 2019.  

A standard should keep pace with the sector it governs. Biochar has grown faster than almost anyone predicted five years ago; our approach to biomass sourcing has grown with it.