GHG Protocol vs SBTi: what each one asks of your Scope 3 data

TL;DR

The GHG Protocol Corporate Value Chain (Scope 3) Standard is the accounting rulebook. It sets out which of the 15 categories you account for, which calculation methods are acceptable, and what you disclose alongside the number.

SBTi is a target framework, not an accounting standard. Its Corporate Net-Zero Standard sets coverage and ambition criteria for the target you submit, and SBTi decides whether a target is validated.

To be report ready under the Protocol: map your categories, pick a method per category, version-lock your emission factors, and write a short methods memo.

To put a Scope 3 target boundary together: calculate coverage against your total Scope 3, show how you will improve the data behind material categories, and put governance around recalculation.

1) GHG Protocol vs SBTi: who asks for what?

The GHG Protocol tells you how to measure and report Scope 3. SBTi tells you what a credible reduction target looks like once you have measured it. Meeting one does not satisfy the other, and neither one signs off the other's work.

SBTi has consulted on a version 2 of the Corporate Net-Zero Standard, so check the criteria published at sciencebasedtargets.org before you fix a target boundary. Validation is SBTi's determination, and whether your inventory holds up is your third-party auditor's.

2) Which Scope 3 method should you use, and when?

Start with whatever gives you complete coverage, then upgrade the categories that carry the footprint. The GHG Protocol Scope 3 Standard names four calculation methods for category 1, purchased goods and services: supplier-specific, hybrid, average-data and spend-based. The ladder below is a practical sequence for moving between them, not a Protocol requirement.

L1 buys coverage. L2 and L3 buy precision where a category is material. L4 is how you attribute a reduction to something you actually did.

3) What data does each Scope 3 category need?

The Protocol accepts any of its calculation methods as long as you disclose the one you used. The minimum column below is the cheapest route to a complete number. The stronger column is what you want sitting behind a category inside a target boundary. Categories 8, 10, 13 and 14 are not listed here: assess them and record the decision either way.

4) How do you document your data sources?

One row per data domain, kept in the same place as the inventory. The first question a third-party auditor asks is where a number came from, and this table is the answer. Fill in the blank columns for your own organisation.

A is activity based, S is spend based, SS is supplier specific.

5) How should you govern emission factors?

Name the factor set, the region and the vintage for every category, then freeze that combination for the base year. Named sets such as DEFRA, EPA, CEDA, Ecoinvent and GaBi each carry their own boundaries and update cycles, so mixing them inside one category without saying so is where consistency breaks. The register below is a template and the bracketed fields are yours to complete.

Version-lock the factor pack used in the baseline, and record any mid-year substitution with the date and the reason.

Ask any factor provider what has been checked and by whom. DitchCarbon's emission factor methodology for spend-based Scope 3 categories 1 and 2 was independently assessed by Globus Thenken in August 2025, and the DitchCarbon Portal calculator is verified to ISO 14064-3 at limited assurance by UL Solutions, renewed annually. Both reports are downloadable from the trust centre.

6) What goes in a methods and assumptions memo?

Seven headings and two or three pages. Write it while you build the inventory rather than the week before someone asks for it.

1. Organisational and operational boundaries.
2. The method used per category, spend based, activity based or supplier specific, and the controls that stop double counting.
3. Electricity treatment, location based and market based, with the certificate criteria you applied.
4. Factor libraries: names, regions, vintages and version IDs.
5. Data gaps and proxies: what is missing, why, and when you will replace it.
6. QA rules, including outlier tests and intensity benchmarks against prior years.
7. Recalculation triggers and thresholds.

7) Which QA rules can you adopt today?

• Completeness. Every one of the 15 categories has a decision recorded against it, included or not relevant, with a reason.
• Double counting. Check category 3 against Scope 1 and 2, category 1 against category 2, and categories 4 and 9 against logistics you run yourself.
• Factor consistency. One geography and one vintage per category unless you justify otherwise.
• Outliers. Flag any site or category that moves more than 30% year on year and investigate before you publish. Set the threshold yourself; 30% is a starting point, not a standard.
• Intensity checks. tCO₂e per unit of revenue, per unit produced and per employee, against the prior year.
• Traceability. Lineage from source system to transformation to factor to result, for every figure.
• Lock and label. Factor pack version and memo version stamped into every export.

Traceability is the rule that decides how your third-party auditor's week goes. Every figure in DitchCarbon carries its source and change history, so an auditor can sample any line and follow it back.

8) What about the common edge cases?

• Inflation distorts spend-based results. Deflate to the base year currency and move your hot spots onto activity data.
• Mixed geographies. Weight regional factors or split the population. Avoid a global average for any category where the grid or the process varies by region.
• Market-based electricity certificates. Define your quality criteria (geography match, vintage, additionality) and disclose where you applied them.
• Homeworking. A kWh per day assumption with regional electricity factors holds up if you document the survey cadence behind it.
• Partial supplier data. Combine supplier-specific data for your largest suppliers with spend or activity methods for the long tail, and label the method line by line.
• PPAs and RECs timing. Align the procurement period with the reporting period, and check you are not counting the same instrument in two entities.

9) When do you have to recalculate your base year?

The GHG Protocol asks you to set a significance threshold in advance and recalculate the base year when a change crosses it. It does not set the number for you, so choose one, state it, and apply it consistently.

Triggers:

• Structural change such as an acquisition, a divestment, outsourcing or insourcing that moves the Scope 3 boundary.
• A factor or method update that would materially shift the base year total.
• A material data correction.
• Misclassification found after the fact, for example spend booked to category 1 that belongs in category 2.

Thresholds: pick a relative threshold as a share of the base year total, and an absolute floor in tCO₂e. Record both in the memo and log every decision against them.

10) How do you ask a supplier for primary data?

Ask for three things rather than thirty, and tell them what you will do with the answer. Use this if you are collecting primary data yourself.

Subject: request for primary emissions data and climate target status

Hello [name],

We are improving the quality of our Scope 3 inventory and would like three things from you:

1. Your latest Scope 1, 2 and 3 inventory, with the base year, the methods and the factor sources.
2. Any plant-level or product-level emission factors relevant to what we buy from you.
3. Your science-based target status, committed or validated, with a link to the evidence.

We will attribute reductions from verified initiatives such as recycled content, renewable energy and logistics mode shifts back to your account. Thank you.

Target status is the part you do not need to ask for, because SBTi publishes it. DitchCarbon runs a free SBTi API so you can look up commitment and validation status per organisation. That dataset is snapshotted weekly.

11) What should a Scope 3 coverage statement say?

A coverage statement names the categories inside the target boundary, the share of total Scope 3 they represent, and the method behind each one. Two blocks to adapt, with the bracketed fields yours to complete.

Coverage. "Our near-term Scope 3 target covers categories [list], which together account for [X]% of total Scope 3 emissions in the [year] base year. Categories [list] are excluded and the rationale is recorded in our methods memo."

Method. "Category 1 is calculated using the spend-based method for the long tail and supplier-specific data for the largest [N] suppliers by spend. Emission factors are [factor set], [region], [vintage year], version-locked for the base year."

Scope 2 sits outside Scope 3, but auditors read the two together, so disclose both the location-based and the market-based figure and state the certificate criteria you applied.

12) FAQs

Do I need supplier-specific data for every supplier?

No. The GHG Protocol Scope 3 Standard accepts spend-based and average-data methods, so put supplier-specific data behind the categories and suppliers that carry your target, and hold the long tail with spend or activity methods. Label the method line by line so an auditor can see which is which.

Can I submit a target built on spend-based data?

SBTi's criteria concern the coverage and ambition of the target rather than mandating one calculation method, and its guidance expects better data where a category is material, together with a plan to improve it. Whether any specific submission is validated is SBTi's decision, so read the criteria in force before you submit.

What is the Scope 3 coverage threshold for SBTi validation?

Under SBTi's Corporate Net-Zero Standard, near-term Scope 3 targets must cover at least 67% of total Scope 3 emissions and long-term targets at least 90%. SBTi has consulted on a version 2 of the standard, so confirm the criteria in force at the point you submit.

What about FLAG?

If land-sector emissions are material in your value chain, SBTi expects separate FLAG accounting and FLAG targets alongside your energy and industry targets.

How DitchCarbon helps with Scope 3 data readiness

DitchCarbon provides verified emissions data for over 2 million organisations, so procurement, sustainability and finance teams can measure and act on supply chain and portfolio emissions from one source. On this job specifically:

• Coverage without a survey round. Map AP and GL spend to organisations and get numbers you can defend within 2 weeks. A recent deployment reached about 60% of a large supplier base within 2 weeks.
• Method upgrades where they matter. Start spend based for completeness, then move material categories onto supplier-specific data.
• Factor registers you can hand over. Region-aware factor libraries with vintages and provenance, and every figure carrying its source and change history.
• Target status, tracked. SBTi commitment and validation status per organisation, snapshotted weekly.
• Governance in the tool. QA rules, outlier flags and a change log against your own materiality thresholds.
• Audit-ready outputs. Boundary statements, methods memos, factor registers and coverage summaries, out of a calculator verified to ISO 14064-3 at limited assurance by UL Solutions.

Build a baseline your targets can stand on

See the Scope 3 coverage DitchCarbon already holds against your own supplier list, and where the gaps are, before you fix a target boundary. See how SBTi-aligned baselining works.

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