ZeroCarbon is PACT conformant: what it means for your product carbon footprints

On 27 October 2026 PACT confirmed that ZeroCarbon passed its conformance tests, and ZeroCarbon is now listed in the PACT Network as a PACT conformant solution. We have written up the announcement separately. This post explains what PACT is, what the tests checked, and what changes for a company that is asked for the carbon footprint of its products.

What PACT is

The Partnership for Carbon Transparency (PACT) is an initiative hosted by the World Business Council for Sustainable Development (WBCSD). It publishes two things that work together: the PACT Methodology, which says how to calculate a product carbon footprint (PCF) consistently, and the PACT Technical Specifications, which say how software systems exchange those footprints through a common data model and API.

The point is interoperability. Without a shared standard, every buyer asks for footprints in its own spreadsheet, and every supplier answers the same question many times in slightly different ways. With PACT, a footprint calculated once can move between any two conformant solutions without re-keying.

What the conformance tests checked

PACT runs its conformance testing tool against a live solution's API and records the results. For Technical Specifications v3.0 the suite has 41 test cases, two of them optional. Our production API passed every mandatory case:

• Authentication. Tokens are issued only for valid credentials, and requests without a valid token are refused.
• Footprints. Listing footprints, fetching one by ID, pagination, and a proper error for an ID that does not exist.
• Filters. By product, company, geography, classification, validity dates and status, combined with AND and OR, including queries that must return nothing and a malformed query that must be rejected.
• Events. A customer asks for a footprint and receives it asynchronously, or receives a rejection for an unknown product, and partners are notified when a footprint is published.
• Transport. Every endpoint refuses plain HTTP.

What changes for suppliers

If you sell to companies that track Scope 3 emissions, you are likely to be asked for product-level footprints, and the request will often name PACT. In ZeroCarbon the path is short:

1. Your bills, invoices and production records become a verified emissions ledger, with each figure linked to its source document.
2. ZeroCarbon calculates the footprint of each product from that ledger under the PACT Methodology v3.0, recording how plant-level emissions were allocated to products.
3. You publish the footprint and grant access to the customers who should see it. Nothing is shared without a grant.
4. Customers using any PACT conformant solution can fetch it, or ask for it through a PACT event, and ZeroCarbon answers automatically.

The same works in the other direction: you can request footprints from your own suppliers in the PACT format, in place of spend-based estimates for purchased goods. How to calculate a product carbon footprint under PACT works through the method with numbers.

What it does not change

PACT is a standard for product footprints across value chains. It does not replace regulatory schemes with their own rules. EU CBAM, for example, defines embedded emissions and its reporting format in its own regulation, and ZeroCarbon handles CBAM separately. The underlying ledger is shared, so the same verified records support both.

Thank you

Thank you to the PACT team at WBCSD for the specifications, the conformance testing service and their help through the process. If a customer has asked you for a PACT footprint, tell us who is asking and we will help you answer it.