Puro Biochar Methodology Edition 2025
Parent concept: Puro CORC200+
Operator: Puro.earth Overview
Project ops / audits: Puro Project Cycle and MRV
Comparison: Puro vs Other Standards
This is the vault’s exhaustive note on Puro’s current biochar methodology: Edition 2022 → 2025 evolution, permanence modeling, eligibility, feedstock, end uses, LCA boundaries, and phase-out dates. Facts below are drawn from the Puro deep-dive research (2026-09-14) and primary PDFs/URLs cited there — not invented.
Primary PDF: Edition 2025 v2 — For Publication
Transition PDF: Methodology Transition Plan for Biochar Edition 2025 (2025-08-10)
Science cross-links while reading: Permanence · Permanence Science for Credits · Properties · Production · Contaminants and Quality · MRV Stack
Versions at a glance
| Version | Approval | Publishing / notes |
|---|---|---|
| Edition 2025 V1 | 12 Jun 2025 (Advisory Board) | Published Document Library 30 Jun 2025. Introduces CORC200+, revised power-law permanence model, stricter Biomass Sourcing Criteria, mobile facility rules, Table 3.2 overhaul. Retail Category R3 initially not CORC-eligible. |
| Edition 2025 v2 | 27 Nov 2025 | Makes retail-to-individuals (Category R3) CORC-eligible under product controls + country-level RDF. (retail update) |
Launch (earliest Facility Audit under Edition 2025): 1 Nov 2025 (extended from 15 Aug 2025 per transition plan).
Exact transition timeline (2022 → 2025)
| Milestone | Date |
|---|---|
| Public consultation | 3–28 Apr 2025 |
| Advisory Board approval (Ed. 2025 V1) | 12 Jun 2025 |
| Publishing (Document Library) | 30 Jun 2025 |
| Launch (earliest Facility Audit under 2025) | 1 Nov 2025 |
| End of transition (last Ed. 2022 Audit Package for pre-launch registrations) | 15 Dec 2025 |
| Edition 2022 termination | 12 Jun 2030 (max 5-year crediting from approval of new edition) |
| Edition 2025 v2 (retail R3 eligible) | Approved 27 Nov 2025 |
Implications by facility stage (transition PDF)
| Facility stage | Rule |
|---|---|
| Already certified under 2022 | May finish current crediting period; renew only against latest edition; optional early upgrade at next Output Audit |
| Registered before Launch, not yet audited | Encouraged to use 2025; allowed 2022 only if complete Audit Package submitted by End of Transition (15 Dec 2025) |
| Registered on/after Launch | Must use Edition 2025 |
| Preliminary Assessments against 2022 | Do not carry over as assessments for 2025 |
Crediting period under Edition 2025: 10 years, renewable twice (via new Facility Audit against latest rules) — contrasted in transition docs with prior 5-year framing often cited for older facilities.
What changed (Edition 2022 → 2025)
Documented changes (methodology intro, permanence post, retail post, transition plan):
| # | Theme | Edition 2022 | Edition 2025 |
|---|---|---|---|
| 1 | Durability claim | CORC100+ | CORC200+ (“several centuries”) |
| 2 | Permanence model | models soil GHG from biochar multi-pool exponential | Revised power model over 200 years, then soil-depth protection assumed for further centuries; 80% confidence interval lower bound; H/C_org domain 0–0.7; soil T floor 7 °C; open-source on GitHub |
| 3 | Random reflectance (Ro) | — | Reporting encouraged; does not affect quantification yet |
| 4 | Biomass sourcing | Prior rules | Stricter alignment with Puro Biomass Sourcing Criteria (category A MSW excluded; category J food crops excluded; category P land-clearing processable but no CORCs; etc.) |
| 5 | Mobile pyrolyzers | Limited treatment | Explicit Stationary vs Mobile facility definitions; spatial extent within one host country; fleet rules |
| 6 | Baselines | — | New Facility / Retrofit / Charcoal Repurpose |
| 7 | Crediting period | Often cited as 5y for legacy facilities in transition docs | 10 years, renewable twice |
| 8 | Use pathways | Prior Table | Table 3.2 overhaul; retail R3 initially not CORC-eligible, then v2 adds safeguards |
| 9 | LCA / leakage / uncertainty | Prior sections | Expanded quantification (project emissions, leakage, monitoring, measurement uncertainty) |
| 10 | Reversal buffer | — | No default buffer for reversal risk (eligibility + evidence; supplier liability if reversal from non-compliance) |
Concept note for the durable-credit claim (without repeating this whole method): Puro CORC200+
Permanence science debate: Permanence Science for Credits · Risks and Controversies
Who can list (supplier eligibility)
- CO₂ Removal Supplier = biochar producer or contracted representative with sole CORC claim rights and end-to-end data access (rules 2.1.1–2.1.3)
- Must comply with methodology + Puro Standard General Rules + local law
- Path: Facility Audit (initial, typically on-site) → Certified Facility → Output Audits (at least annually) → CORC issuance
Operational detail: Puro Project Cycle and MRV
Feedstock rules (Biomass Sourcing Criteria)
Categories that can potentially generate CORCs (non-exhaustive)
Allowed categories potentially generating CORCs include:
| Code | Description (high level) |
|---|---|
| B | Sorted food waste |
| C | Sorted MSW fractions other than food |
| D | Green waste |
| E | Animal waste |
| F | Municipal sludge / biosolids |
| G | Forest biomass meeting BSC |
| H | Pulp/paper sludge |
| I | Non-food ag crops with land-use limits |
| K | In-field residues |
| L | Non-field processing residues |
| M | Palm residuals |
| N | Conservation / invasive biomass |
| O | Aquatic biomass |
Not allowed / no CORCs
| Code | Rule |
|---|---|
| A | Mixed unsorted MSW — not allowed |
| J | Food / feed crops — not allowed |
| P | Land-clearing biomass — may be processed but shall not issue CORCs |
Additional operational feedstock rules
- No co-firing with fossil coal/oil in feedstock
- Impurity & fossil-C accounting (plastics, paints, sludge fossil C)
- Stockpiling CH₄ controls
- Biohazard treatment (≥500 °C × 3 min if relying on carbonization)
Cross-link: MRV Stack · Contaminants and Quality · Production
Production requirements
- Thermochemical conversion: pyrolysis / gasification / modified combustion / other
- H/C_org < 0.70 mandatory (rule 3.5.1) — hard gate for quantification eligibility
- Reactor categorization: mode, process, heating, streams, co-product fate
- Combustion of volatiles: design for complete combustion; ≥95% normal combustion operating time; flameout procedures; CH₄/N₂O monitoring rules
- Fossil fuel use allowed for ignition/support if no fossil C enters biochar and LCA includes emissions (coal as process fuel not allowed)
Facility baselines under Edition 2025:
| Baseline type | Intent |
|---|---|
| New Facility | Greenfield / new installation |
| Retrofit Facility | Conversion / upgrade of existing equipment |
| Charcoal Repurpose | Prior charcoal production redirected into eligible CDR pathway |
Retrofit / charcoal-repurpose baselines deduct prior char storage via Eqs. 6.6–6.9 (see quantification section below).
Mobile rules (Edition 2025): explicit Stationary vs Mobile facility definitions; spatial extent within one host country; fleet rules. Common US pitfall when units cross state lines that imply multi-country or unclear host-country scope — see Puro Project Cycle and MRV.
End uses (Table 3.2 highlights)
Point of CORC creation = first durable eligible use (rule 2.3.1) — i.e., ex-post relative to application, not at factory gate alone. Ownership/double-counting: Double Counting and Credit Ownership.
CORC-eligible examples
| Family | Examples |
|---|---|
| Agriculture / soil (AF*) | Soil amendment pure/mixed (AF1–AF2); cultivation/planting substrates (AF3–AF4); seed coatings (AF5) |
| Animal / husbandry (AH*) | Animal bedding / manure additives / feed cascades with safeguards |
| Waste / landfill (WM*) | Waste/landfill uses with evidence |
| Environmental remediation (EM*) | Remediation pathways |
| Built environment (BE*) | Built-environment soils / materials / road surfacing |
| Natural environment (NE1) | Certain natural-environment soil uses with conditions |
| Retail / landscaping | Landscaping retail (R4); under v2, retail-to-individuals (R3) with product controls + country-level RDF |
Not CORC-eligible (examples)
| Pathway | Status |
|---|---|
| Addition to water systems (NE2) | Not CORC-eligible |
| Pet feed / cosmetics / short-lived retail (R1 etc.) | Not CORC-eligible |
| Industrial fuel | Explicitly not removal |
| Short-lived industrial materials (IMF2/IMF3) | Not CORC-eligible |
| Fuel / biocoke uses | Explicitly not removal |
Honesty note: Exact Table 3.2 rows beyond those extracted should be read from the official PDF for project design.
Retail Category R3 (v2, Nov 2025)
Eligible for CORCs only with:
- Product-level particle size / moisture controls
- Consumer labelling
- Contractual clarity with last tracked intermediary
- Country-level reversal-risk discount (RDF) on (C_{\mathrm{stored}})
- Conservative transport accounting
Source: Dec 2025 retail update
Even with v2 safeguards, consumer channels remain higher-risk than contracted farm application (Risks and Controversies).
Additionality / baseline
Three components (rule 3.3.1):
- Carbon additionality
- Regulatory additionality
- Financial additionality
Per Puro Additionality Assessment Requirements + Baseline and Additionality Questionnaire (made public after successful Facility Audit).
Biochar-specific financial analysis must cover:
- Biochar sales prices
- Co-product revenues
- Cost structure
Pitfall: waste-treatment cost-saving projects may fail financial additionality if savings alone make the project viable without CORCs (rule 3.3.4). See Puro Project Cycle and MRV · Risks and Controversies.
Lifecycle emissions, leakage, and net CORCs
Overall equation (5.2.1):
[ \mathrm{CORCs} = C_{\mathrm{stored}} - C_{\mathrm{baseline}} - C_{\mathrm{loss}} - E_{\mathrm{project}} - E_{\mathrm{leakage}} ]
| Term | Meaning |
|---|---|
| (C_{\mathrm{stored}}) | Stored biochar C as CO₂e: (Q_{\mathrm{biochar}} \times C_{\mathrm{org}} \times 44/12) (Eq. 6.1) |
| (C_{\mathrm{baseline}}) | Removals that would have occurred anyway (incl. retrofit / charcoal-repurpose deductions via Eqs. 6.6–6.9) |
| (C_{\mathrm{loss}}) | Expected decay losses via persistence fraction PF (Eq. 6.3 conceptually: (C_{\mathrm{stored}} \times (100 - PF)/100) with PF in %) |
| (E_{\mathrm{project}}) | Full LCA operational + embodied emissions; allocation to co-products; cut-offs |
| (E_{\mathrm{leakage}}) | Identify, mitigate, quantify residual market/activity-shifting leakage |
Net CDR logic in words: Stored biochar C (as CO₂e) minus expected decay losses minus baseline removals that would have occurred anyway minus project LCA emissions minus unmitigated leakage — only for biochar proven in an eligible end use.
LCA / MRV operational stack: Puro Project Cycle and MRV · MRV Stack
Permanence & quantification (Edition 2025)
Persistence fraction
[ PF = M - a \times (H/C_{\mathrm{org}}) \quad (\mathrm{Eq.\ 6.4}) ]
(M) and (a) from Table 6.1 by mean annual soil temperature (T_s) (°C). Examples from the deep dive:
| (T_s) | (M) | (a) |
|---|---|---|
| 7 °C (floor) | 96.59 | 11.28 |
| 15 °C | 91.87 | 28.16 |
| 20 °C | 89.87 | 35.29 |
| 30 °C | 87.66 | 43.10 |
| 40 °C | 86.19 | 48.25 |
Model design choices:
- Soil T from Puro-provided dataset (SBIO1 annual mean 5–15 cm); minimum 7 °C
- 200-year power-law extrapolation; thereafter deeper-soil protection assumed → CORC200+
- Uses lower bound of 80% CI (program-level conservatism)
- H/C_org domain 0–0.7
- Open source: https://github.com/puro-earth/PuroBiocharPersistenceEdition2025 (built on SLU
biocharStability)
Worked intuition (from deep dive):
| Soil T | H/C_org | Approx PF |
|---|---|---|
| 20 °C | 0.4 | (89.87 - 35.29 \times 0.4) ≈ 75.8% |
| 20 °C | 0.2 | ≈ 82.8% |
Lab metrics for quantification
| Metric | Role |
|---|---|
| C_org ((C_{\mathrm{tot}} - C_{\mathrm{inorg}})) | Required for (C_{\mathrm{stored}}) |
| H → H/C_org | Required for PF; gate < 0.70 |
| Dry mass free of impurities | Required mass basis |
| Ro / petrography | Optional complementary reporting (rules 6.2.5–6.2.6); not in CORC math yet |
| Contaminant / environmental quality | Table 3.2 points to WBC class thresholds (e.g., WBC Agro for soil) where local regulation is absent |
Sampling cadence, accredited lab preference, and standards (ISO 16948, ASTM D5373, etc.): Puro Project Cycle and MRV
Science anchors:
- Puro permanence post
- Woolf et al. 2021 — DOI 10.1021/acs.est.1c02425
- inertinite permanence benchmark — DOI 10.1016/j.coal.2023.104409
- Azzi et al. 2024 — DOI 10.1016/j.geoderma.2023.116761
- Vault: Permanence · Permanence Science for Credits · Properties
Puro’s permanence stance vs millennial claims
Puro explicitly stopped at centuries, not millennia, pending integration of inertinite/Ro science (permanence post). Ro is encouraged for reporting but does not change CORC quantification under Edition 2025. Contrast with Isometric Biochar Protocol (200y or Ro≥2% → 1000y) and CSI Global Biochar C-Sink (upper GPC path via Ro≥3.8% or HyPy≥90%). Concept note: Puro CORC200+.
Reversal policy
- No default buffer deduction (rule 4.2.1)
- Risks managed via use eligibility + evidence
- Supplier liable for reversals caused by non-compliance
Critics may prefer pooled buffers — see Risks and Controversies · Puro vs Other Standards.
Crediting period and renewals
| Item | Edition 2025 |
|---|---|
| Initial crediting period | 10 years |
| Renewals | Twice, via new Facility Audit against latest rules |
| Edition 2022 hard stop | 12 Jun 2030 |
Capacity expansion of similar reactors may be possible without resetting period (rules 3.1.6–3.1.8 — detail in Puro Project Cycle and MRV).
ICVCM status for this methodology
As of ICVCM announcement 2025-12-11 and research date 2026-09-14:
- Puro program is CCP-Eligible (General Rules v4.2+)
- Biochar methodology is not yet CCP-Approved
Buyers wanting CCP-labelled credits today may prefer Verra VM0044 until Puro’s category assessment completes. Re-check ICVCM Assessment Status before relying on this. See Puro.earth Overview · Puro vs Other Standards.
When this methodology is the right fit
Prefer Edition 2025 / CORC200+ when you want:
- Mature BCR buyer recognition + CORCCHAR price signal + Nasdaq registry infrastructure
- Flexible baselines (New / Retrofit / Charcoal Repurpose) and explicit mobile fleet rules
- A centuries-scale (200+) permanence claim with open-source PF model
Consider alternatives when you need CCP methodology labels today (Verra VM0044), a 1000-year Ro path (Isometric Biochar Protocol), or EBC/WBC-native GPC/SPC (CSI Global Biochar C-Sink). Full chooser: Puro vs Other Standards.
Primary citations (URLs / DOIs from research)
- Edition 2025 v2 PDF
- Transition plan PDF
- Permanence science
- Retail v2 update
- Persistence model — https://github.com/puro-earth/PuroBiocharPersistenceEdition2025
- Woolf et al. 2021 — https://doi.org/10.1021/acs.est.1c02425
- Sanei et al. 2024 — https://doi.org/10.1016/j.coal.2023.104409
- Azzi et al. 2024 — https://doi.org/10.1016/j.geoderma.2023.116761
- Document library
- Fees / journey
Also listed in Key Sources.
See also
Puro CORC200+ · Puro.earth Overview · Puro Project Cycle and MRV · Puro Pricing and CORC Indexes · Puro vs Other Standards · MRV Stack · Permanence Science for Credits · Permanence · Biochar as Durable CDR · Verra VM0044 · Isometric Biochar Protocol · CSI Global Biochar C-Sink · Risks and Controversies · Double Counting and Credit Ownership · Contaminants and Quality · Production · Properties · Carbon Markets Hub · Key Sources