Grain Ecosystem

Before you read this article, please read 

Agricultural residues can be climate-positive feedstocks, but verifying sustainability requires careful attention to land use, soil health, and sourcing transparency.  

Puro.Earth applies the same sustainability criteria to both food and non-food agricultural crops. To meet these requirements, projects must clearly document the origin, type, and traceability of each feedstock delivery. For every batch received, they must record basic details such as the delivery date, quantity, transporter, and delivery location. They also need to specify the type of crop, the crop part used, moisture level at delivery, and typical carbon content. Traceability is key: projects must describe the full supply chain, including all intermediaries, and provide geographic sourcing details precise enough to prove the feedstock meets sustainability criteria. If multiple biomass sources are mixed, data must be retained to apply a mass-balance approach to determine which portion of the mix is eligible. Whenever possible, keeping eligible and non-eligible biomass separate along the supply chain is preferred, as it simplifies sustainability verification. Criteria to be evidenced are: 

To prove these criteria, projects can provide: 

If the feedstock consists of in-field agricultural residues (such as cereal straw or pruning waste) Puro.Earth requires extra documentation to ensure these materials are collected responsibly. Projects must: 

To prove these criteria, projects can submit: 

Verra Verified Carbon Standard (Verra VCS) 

For projects using agricultural waste biomass sourced directly from fields —rather than from centralized processing facilities— Verra requires evidence that the activity does not degrade soil health. Specifically, projects must provide documentation showing that biomass removal does not reduce soil carbon stocks or crop productivity, or that the baseline scenario involved the open burning of residues without energy recovery. If such documentation is unavailable, Verra imposes a strict limit: no more than 50% of total residues may be removed from the field, in order to safeguard against soil degradation. 

CAR assumes that the business-as-usual fate for agricultural waste is combustion or decomposition. Eligible agricultural feedstocks include: 

1. Harvest residues (e.g. straw, stalks, husks) 

2. Orchard, vineyard, and woody biomass prunings or orchard/vineyard renewal clearings. Projects must demonstrate that biomass removal is part of a normal management cycle or operation. 

3. Fruit and vegetable residues, including nut shells. No specific environmental safeguards apply. 

For agricultural feedstocks specifically, the project must demonstrate that the material qualifies as an agricultural residue or waste, meaning it is a by-product generated alongside a primary marketable crop, not produced intentionally for biochar. 

In the case of agricultural crop residues, the project must also ensure that the biomass is not sourced from the same acreage in consecutive years. This must be stipulated in the purchase contract between the Project and the feedstock supplier. Alternatively, if the feedstock is sourced from the same land in sequential years, the project must provide evidence that the land has been monocropped (with no crop rotation) for at least five years. 

For non-forestry feedstocks, the project must also prove that the biomass was not intentionally grown for energy production and does not have a likely alternative use as an energy source. To meet this requirement, the Project must carry out an analysis of how that type of biomass is typically used in the region. This analysis must show that one of the following conditions is true: (1) Less than 50% of the total harvested biomass —both in terms of volume and value— is used for energy production in the region. This can be done by demonstrating that the feedstock is not sourced from within 50 km of a cellulosic ethanol plant, or providing farm-level documentation proving that the supplier has not previously delivered biomass to any cellulosic ethanol facility. (2) The biomass has already fulfilled its energy purpose, such as manure that has been used in anaerobic digestion before being sourced for the project. 

The bottom line? Feedstock eligibility isn’t just about what the material is, it’s also about how you prove it. That means: 

Your sustainability claim is only as strong as the evidence that backs it. 

Table S10. You can also download the full PDF 

Table S10

This article expands on the main guide “Securing Your Feedstock: How to Prove it’s Sustainable” with specific requirements for agricultural residues.

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<p></p><p><em>Before you read this article, please read </em><a href="https://grainecosystem.com/knowledge-hub/articles/68af5254b1d72ab2d7467ef7" target="_blank" rel="noopener noreferrer"><em>Securing Your Feedstock: How to Prove it’s Sustainable</em></a><em> </em></p><p>Agricultural residues can be climate-positive feedstocks, but verifying sustainability requires careful attention to land use, soil health, and sourcing transparency.  </p><h2>What You Need to Prove </h2><ul class="bullet"><li value=1>Material is a residue, not co-product or purpose-harvested biomass </li></ul><ul class="bullet"><li value=1>Removing it does not harm soil health or fertility </li></ul><ul class="bullet"><li value=1>Feedstock has no alternative high-value use (like fodder or bioenergy) </li></ul><ul class="bullet"><li value=1>Traceability to farm or aggregation point </li></ul><h2>Accepted Proof by Standard </h2><h3>Puro.Earth</h3><p>Puro.Earth applies the same sustainability criteria to both food and non-food agricultural crops. To meet these requirements, projects must clearly document the origin, type, and traceability of each feedstock delivery. For every batch received, they must record basic details such as the delivery date, quantity, transporter, and delivery location. They also need to specify the type of crop, the crop part used, moisture level at delivery, and typical carbon content. Traceability is key: projects must describe the full supply chain, including all intermediaries, and provide geographic sourcing details precise enough to prove the feedstock meets sustainability criteria. If multiple biomass sources are mixed, data must be retained to apply a mass-balance approach to determine which portion of the mix is eligible. Whenever possible, keeping eligible and non-eligible biomass separate along the supply chain is preferred, as it simplifies sustainability verification. Criteria to be evidenced are: </p><ul class="bullet"><li value=1>Legality: The crops must be grown in line with local laws and regulations. </li></ul><ul class="bullet"><li value=1>Worker Safety: Safe working conditions must be ensured during both planting and harvesting. </li></ul><ul class="bullet"><li value=1>Protection of Natural Areas: Crops cannot be grown on land that was a forest, wetland, peatland, or other high-carbon or high-biodiversity area after January 1, 2008. Only land already used for agriculture before that date is allowed. </li></ul><ul class="bullet"><li value=1>Carbon Stock Preservation: The way these crops are grown must help maintain or increase the amount of carbon stored in the soil and land over time. </li></ul><ul class="bullet"><li value=1>No Competition with Food or Feed: Crops can be grown on degraded, marginal, or contaminated land if these are officially recognized as such by local authorities. If the land is suitable for growing food or feed, these crops are only allowed if they’re used as cover crops or intermediary crops (i.e., not replacing food production). Exceptions are made if the CDR crop itself is a food or feed product; or if the land has already been used to grow bioenergy crops (like corn) for more than 20 years before the CDR project starts. </li></ul><ul class="bullet"><li value=1>Environmentally Responsible Farming: New crop projects started after 2020 must follow national or recognized best-practice farming guidelines, protecting soil and water, using fertilizers and pesticides responsibly, and supporting biodiversity. Older crop operations (before 2021) that are now being repurposed for CDR are encouraged to follow these practices, but it’s not mandatory. </li></ul><ul class="bullet"><li value=1>Minimal Impact on Nearby Areas: Projects must avoid causing indirect environmental damage nearby, such as changes to water flow or vegetation that would reduce carbon storage or increase emissions. </li></ul><ul class="bullet"><li value=1>Respect for Indigenous Communities: If crops are sourced in areas where Indigenous peoples live, the project must not interfere with the land or resources essential to their basic needs. </li></ul><p>To prove these criteria, projects can provide: </p><ul class="bullet"><li value=1>Certifications of good farming practices </li></ul><ul class="bullet"><li value=1>Proof of compliance with regulations like the EU RED III or Paris Agreement, </li></ul><ul class="bullet"><li value=1>Evidence of local land-use laws or agricultural policies </li></ul><ul class="bullet"><li value=1>Direct documentation from the feedstock supplier (especially for legality, worker safety, carbon stock, Indigenous impacts, and farming practices), </li></ul><ul class="bullet"><li value=1>Official land records or maps showing the land type and use history to confirm it doesn’t conflict with food production or ecosystem protection. </li></ul><p>If the feedstock consists of in-field agricultural residues (such as cereal straw or pruning waste) Puro.Earth requires extra documentation to ensure these materials are collected responsibly. Projects must: </p><ul class="bullet"><li value=1>Preserve soil quality and carbon stocks by leaving a portion of residues in the field (e.g., roots in place or minimum cutting height) or follow applicable local regulations on residue harvesting </li></ul><ul class="bullet"><li value=1>Ensure safe working conditions during collection and handling of residues </li></ul><p>To prove these criteria, projects can submit: </p><ul class="bullet"><li value=1>Primary documentation from the feedstock supplier explaining the practices in place </li></ul><ul class="bullet"><li value=1>Local or national policies, plans, or laws that regulate residue harvesting and labor practices </li></ul><ul class="bullet"><li value=1>Evidence that these regulations are monitored and enforced </li></ul><h3>Verra Verified Carbon Standard (Verra VCS) </h3><p>For projects using agricultural waste biomass sourced directly from fields —rather than from centralized processing facilities— Verra requires evidence that the activity does not degrade soil health. Specifically, projects must provide documentation showing that biomass removal does not reduce soil carbon stocks or crop productivity, or that the baseline scenario involved the open burning of residues without energy recovery. If such documentation is unavailable, Verra imposes a strict limit: no more than 50% of total residues may be removed from the field, in order to safeguard against soil degradation. </p><h3>Climate Action Reserve (CAR) </h3><p>CAR assumes that the business-as-usual fate for agricultural waste is combustion or decomposition. Eligible agricultural feedstocks include: </p><p>1. Harvest residues (e.g. straw, stalks, husks) </p><ul class="bullet"><li value=1>Retention of a minimum amount of residue is required to maintain soil organic carbon and site productivity. </li></ul><ul class="bullet"><li value=1>You must document that residue removal does not exceed the limits identified by crop type in Table S10 of Karan et al. (2023). (See Table at the end of the article). </li></ul><ul class="bullet"><li value=1>For crops not listed, a default 30% maximum removal limit applies. </li></ul><ul class="bullet"><li value=1>Exceptions are allowed if biochar from the project is returned to the same site in amounts that replenish the excess carbon removed. </li></ul><p>2. Orchard, vineyard, and woody biomass prunings or orchard/vineyard renewal clearings. Projects must demonstrate that biomass removal is part of a normal management cycle or operation. </p><p>3. Fruit and vegetable residues, including nut shells. No specific environmental safeguards apply. </p><h3>Isometric</h3><p>For agricultural feedstocks specifically, the project must demonstrate that the material qualifies as an agricultural residue or waste, meaning it is a by-product generated alongside a primary marketable crop, not produced intentionally for biochar. </p><p>In the case of agricultural crop residues, the project must also ensure that the biomass is not sourced from the same acreage in consecutive years. This must be stipulated in the purchase contract between the Project and the feedstock supplier. Alternatively, if the feedstock is sourced from the same land in sequential years, the project must provide evidence that the land has been monocropped (with no crop rotation) for at least five years. </p><p>For non-forestry feedstocks, the project must also prove that the biomass was not intentionally grown for energy production and does not have a likely alternative use as an energy source. To meet this requirement, the Project must carry out an analysis of how that type of biomass is typically used in the region. This analysis must show that one of the following conditions is true: (1) Less than 50% of the total harvested biomass —both in terms of volume and value— is used for energy production in the region. This can be done by demonstrating that the feedstock is not sourced from within 50 km of a cellulosic ethanol plant, or providing farm-level documentation proving that the supplier has not previously delivered biomass to any cellulosic ethanol facility. (2) The biomass has already fulfilled its energy purpose, such as manure that has been used in anaerobic digestion before being sourced for the project. </p><h2>Final Takeaways </h2><p>The bottom line? Feedstock eligibility isn’t just about what the material is, it’s also about how you prove it. That means: </p><ul class="bullet"><li value=1>Clear origin and traceability </li></ul><ul class="bullet"><li value=1>Defined and documented baseline fate </li></ul><ul class="bullet"><li value=1>Proof that it’s a residue or waste, not displacing more valuable uses </li></ul><ul class="bullet"><li value=1>Strong environmental safeguards </li></ul><ul class="bullet"><li value=1>Chain-of-custody documentation aligned with registry requirements </li></ul><p>Your sustainability claim is only as strong as the evidence that backs it. </p><h2>Sources</h2><ul class="bullet"><li value=1><a href="https://7518557.fs1.hubspotusercontent-na1.net/hubfs/7518557/Puro%20Biochar%20Methodology%20-%20Edition%202025%20-%20Approved%20Version%20-%20Pending%20Copy%20Edit.pdf" target="_blank" rel="noopener noreferrer">Puro.Earth. (June, 2025). Biochar Methodology, Edition 2025 V1.</a> </li></ul><ul class="bullet"><li value=1><a href="https://7518557.fs1.hubspotusercontent-na1.net/hubfs/7518557/Biochar%20Public%20Consultation%202025/02_Puro%20Biomass%20Sourcing%20Criteria%20v1.1%20-%20Draft%20for%20consultation.pdf" target="_blank" rel="noopener noreferrer">Puro.Earth (2025) Biomass Sourcing Criteria.</a> </li></ul><ul class="bullet"><li value=1><a href="https://verra.org/methodologies/vm0044-biochar-utilization-in-soil-and-non-soil-applications-v1-2/" target="_blank" rel="noopener noreferrer">Verra (June, 2025). VM0044 Biochar Utilization in Soil and Non-Soil Applications, v1.2</a> </li></ul><ul class="bullet"><li value=1><a href="https://www.climateactionreserve.org/wp-content/uploads/2024/03/CAR-Eligible-Biochar-Feedstocks-List-2024-03-19.pdf" target="_blank" rel="noopener noreferrer">Climate Action Reserve. (March, 2024). Eligible Biochar Feedstock List.</a> </li></ul><ul class="bullet"><li value=1><a href="https://registry.isometric.com/module/biomass-feedstock-accounting" target="_blank" rel="noopener noreferrer">Isometric (2024). Biomass Feedstock Accounting.</a>  </li><li value=2><a href="https://onlinelibrary.wiley.com/doi/epdf/10.1111/gcbb.13102" target="_blank" rel="noopener noreferrer"> Karan, S. K., Woolf, D., Azzi, E. S., Sundberg, C., & Wood, S. A. (2023). Potential for biochar carbon sequestration from crop residues: A global spatially explicit assessment. GCB Bioenergy, 15(12), 1424-1436, DOI: 10.1111/gcbb.13102</a></li><li value=3><a href="https://onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1111%2Fgcbb.13102&file=gcbb13102-sup-0001-Supinfo.pdf" target="_blank" rel="noopener noreferrer">Karan, et. al. (2023). Supplement.</a></li></ul><h2>Annex</h2><p>Table S10. You can also download the full PDF <a href="https://onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1111%2Fgcbb.13102&file=gcbb13102-sup-0001-Supinfo.pdf" target="_blank" rel="noopener noreferrer">here</a> (p. 10).</p><img src="/media/TableS10.jpg" alt="TableS10.jpg" width="864"  height="1015"/><h2>Related content</h2><ul class="bullet"><li value=1><a href="https://grainecosystem.com/knowledge-hub/articles/68af5254b1d72ab2d7467ef7" target="_blank" rel="noopener noreferrer">Securing Your Feedstock: How to Prove it’s Sustainable </a></li></ul><ul class="bullet"><li value=1><a href="https://grainecosystem.com/knowledge-hub/articles/67362abaea63cff8e65976e2" target="_blank" rel="noopener noreferrer">Biochar: Feedstock Sourcing & Eligibility for every Standard</a> </li></ul><ul class="bullet"><li value=1><a href="https://grainecosystem.com/knowledge-hub/articles/674763fc0f29280cdf023b34" target="_blank" rel="noopener noreferrer">How to Choose the Best Methodology for your Biochar Project</a> </li></ul><ul class="bullet"><li value=1><a href="https://grainecosystem.com/knowledge-hub/articles/688a6eb62492b585355e9fd3" target="_blank" rel="noopener noreferrer">The Importance of Laboratory Testing in Biochar Projects</a> </li></ul><ul class="bullet"><li value=1><a href="https://grainecosystem.com/knowledge-hub/articles/6814f3dae44bb4f2fc862292" target="_blank" rel="noopener noreferrer">How to Understand your Biochar Quality</a> </li></ul>

Agricultural Residues: Sustainability Criteria by Standard