What Does a Supplier Carbon Assessment Include? A Factory-Level Checklist

A supplier carbon assessment at factory level should cover six areas: the site and its boundaries, energy use by source and process, direct emissions from fuels, processes and refrigerants, electricity sourcing, material inputs and precursors, and the quality of the data behind all of it. A good assessment ends with a site emissions estimate, an allocation to the products you buy, and a short list of reduction opportunities with owners. The checklist below sets out what to ask for, what evidence to see and which gaps to flag.

Buyers often use supplier questionnaires to collect this information, but a questionnaire only records what a supplier says. An assessment, whether on site or remote with document review, tests whether the numbers hold up and shows where emissions can be cut. That makes it the core tool for decarbonising the few suppliers that drive most of a category’s footprint.

Before the assessment: agree scope and method

Agree three things with the supplier in advance:

• Boundary. Which site or sites, which production lines, and whether the assessment covers the whole facility or only the lines making your products.
• Accounting basis. Use the GHG Protocol Corporate Standard or ISO 14064-1:2018 for site-level emissions 1 2, and ISO 14067:2018 where a product carbon footprint is required 5. In China, the national product footprint standard GB/T 24067-2024 is adapted from ISO 14067 10.
• Reporting period. Normally the most recent full calendar or financial year, with monthly data where available.

Send the document request at least two weeks before the visit. Most delays happen because records are held by different departments, such as finance for invoices, facilities for meters and production for output.

1. Site profile and boundaries

• Legal entity, address and ownership of the site
• Products made, production lines and annual output by product or product family
• Share of site output supplied to you
• Operating hours, shifts and seasonal patterns
• Outsourced processes (plating, heat treatment, dyeing, painting) and who performs them
• Any on-site third parties, such as a utility operating a boiler or solar array

Watch for: boundaries that change between years, and outsourced processes left out of the footprint.

2. Energy use by source and process

• Monthly electricity consumption from utility bills, with meter numbers
• Fuel purchases by type (coal, natural gas, LPG, diesel, fuel oil, biomass) with invoices
• Purchased steam or heat, and its supplier
• Sub-metering by process or major equipment, where it exists
• Energy management system certification, if any
• Results of past energy audits

An energy audit is often the quickest route from assessment to action. ISO 50002-1:2025 sets out general requirements for energy audits and defines levels from walk-through assessments to detailed engineering studies 4. Ask whether an audit has been done and whether its recommendations were implemented.

Watch for: fuel bought for several sites on one invoice, and diesel for generators or vehicles missing from records.

3. Direct emissions: combustion, process and refrigerants

• Stationary combustion in boilers, furnaces, kilns, ovens and dryers
• Mobile combustion in on-site vehicles and forklifts
• Process emissions from chemical reactions, such as carbonate decomposition, anode consumption or chemical processes
• Refrigerant inventory: equipment list, gas type, charge size and top-up records
• Other greenhouse gases used in processes, such as SF₆ in switchgear or fluorinated gases in electronics manufacturing

The GHG Protocol covers seven greenhouse gases: CO₂, CH₄, N₂O, HFCs, PFCs, SF₆ and NF₃ 1. Refrigerant and process-gas leaks are often missed but can be material because of their high global warming potential. Top-up purchase records are a practical proxy for leakage.

Watch for: refrigerants recorded as maintenance costs with no quantity, and emission factors with no stated source.

4. Electricity sourcing and Scope 2

• Grid region and the emission factor applied
• On-site generation (rooftop solar, combined heat and power) and metered output
• Renewable electricity contracts, green power trading or energy attribute certificates, with retirement evidence
• Whether both location-based and market-based figures are calculated

The GHG Protocol requires dual reporting of location-based and market-based Scope 2. It is revising its Scope 2 guidance, including proposals for hourly matching and deliverability in market-based reporting, with final publication expected in 2027 3. Check claims against today’s rules, and note which instruments may be affected by the changes.

For Chinese sites, use the national electricity carbon footprint factor published by the Ministry of Ecology and Environment (0.6205 kg CO₂e/kWh for 2023) as a consistent default where no better factor applies 8. Green electricity certificates (GECs) are now the only renewable electricity certificate in China and have been recognised by RE100 since May 2025 9.

Watch for: certificates claimed without retirement records, and renewable percentages that do not reconcile with invoices.

5. Materials, precursors and inbound inputs

• Main raw materials and purchased components by weight
• Recycled content, with supporting documentation
• Emission factors or supplier data used for materials, and their sources
• Carbon-intensive precursors (steel, aluminium, clinker, chemicals, yarn) and whether supplier-specific data exists
• Packaging materials
• Production waste, scrap rates and how scrap is handled

For many manufactured products, materials outweigh the factory’s own energy use in the product footprint. If goods fall under the EU CBAM, precursor emissions must be calculated using the EU methodology and verified by an accredited verifier 7.

Watch for: recycled content claims with no chain-of-custody evidence, and high scrap rates that inflate material use per unit.

6. Allocation to your products

• Method for allocating site emissions to products (mass, units, machine hours or economic value)
• Reason for the chosen method and its consistency over time
• Product-level footprint for items you buy, if calculated
• Format of any product carbon footprint shared

Allocation is where site data becomes useful to a buyer. Ask for product footprints in a format aligned with the PACT Methodology, which WBCSD updated to Version 3 in June 2026 to support product-level data exchange 6.

Watch for: allocation by revenue for physically similar products, which can shift emissions towards lower-value lines.

7. Data quality and governance

• Who compiles the data and who approves it
• Share of figures based on measured data versus estimates or defaults
• Meter calibration records
• Previous third-party verification or certification, including its scope and date
• Changes in method since previous years
• Data held for other customers or schemes, such as a national ETS or listed-company disclosure

Rate each major data point as measured, calculated from records, estimated or default. This matters more than the headline number, because it tells you how much weight a sourcing decision can bear.

8. Reduction opportunities and commitments

• Existing targets or decarbonisation plans
• Reduction projects completed in the last three years, with evidence
• Opportunities identified during the assessment: efficiency, fuel switching, heat recovery, electrification, renewable electricity, material changes
• Barriers such as capital, site ownership, grid constraints or technical capacity
• Agreed next steps, with an owner and date for each

Estimate the emissions effect of each opportunity where possible, but do not promise the supplier cost savings or paybacks that have not been worked through with them.

After the assessment

Share a written summary with the supplier within a few weeks. Include the site emissions estimate, data-quality ratings, the main gaps and the agreed actions. Then:

• update your Scope 3 baseline for purchased goods and services with the supplier-specific figures, recording the change of method;
• add agreed actions and data improvements to the supplier’s business review agenda;
• schedule a follow-up, usually annually, or sooner if a major project is under way.

For how assessments fit into a wider programme, see our 90-day supplier decarbonisation pilot plan. If you need factory-level assessments for suppliers in China, Hong Kong, Taiwan or elsewhere in APAC, talk to our team.

Sources

1. GHG Protocol, “Corporate Accounting and Reporting Standard”. https://ghgprotocol.org/corporate-standard
2. ISO, “ISO 14064-1:2018 Greenhouse gases — Part 1: Specification with guidance at the organization level for quantification and reporting of greenhouse gas emissions and removals”, December 2018. https://www.iso.org/standard/66453.html
3. GHG Protocol, “GHG Protocol Opens Public Consultations on Scope 2 and Electricity Sector Consequential Accounting”, 20 October 2025. https://ghgprotocol.org/blog/release-ghg-protocol-opens-public-consultations-scope-2-and-electricity-sector-consequential
4. ISO, “ISO 50002-1:2025 Energy audits — Part 1: General requirements with guidance for use”, June 2025. https://www.iso.org/standard/83645.html
5. ISO, “ISO 14067:2018 Greenhouse gases — Carbon footprint of products — Requirements and guidelines for quantification”, August 2018. https://www.iso.org/standard/71206.html
6. WBCSD, “PACT Methodology Version 3”, 2 June 2026. https://www.wbcsd.org/resources/pact-methodology-version-3/
7. European Commission, Taxation and Customs Union, “Verification of CBAM emissions”. https://taxation-customs.ec.europa.eu/carbon-border-adjustment-mechanism/cbam-verification_en
8. Sino-German Cooperation on Climate Change (GIZ), “China releases 2025 report on product carbon footprint management”, 11 July 2025. https://climatecooperation.cn/climate/china-releases-2025-report-on-product-carbon-footprint-management/
9. State Council Information Office, “China’s green system wins key approval”, 20 May 2025. http://english.scio.gov.cn/chinavoices/2025-05/20/content_117884420.html
10. SESEC, “China Releases Guidelines for Product Carbon Footprint Accounting”. https://sesec.eu/china-releases-guidelines-for-product-carbon-footprint-accounting/