Information and Communication Technologies (ICT) have a significant climate impact, and data centres account for a large proportion of the carbon emissions from ICT. To achieve sustainability goals, it is important that all parties involved in ICT supply chains can track and share accurate carbon emissions data with their customers, investors, and the authorities.

However, businesses have strong incentives to make their numbers look good, whilst less so to publish their accounting methods along with all the input data, due to the risk of revealing sensitive information. It would be uneconomical to use a trusted third party to verify the data for every report for each party in the chain. As a result, carbon emissions reporting in supply chains currently relies on unverified data.

This paper proposes a methodology that applies cryptography and zero-knowledge proofs for carbon emissions claims that can be subsequently verified without the knowledge of the private input data. The proposed system is based on a zero-knowledge Succinct Non-interactive ARguments of Knowledge (zk-SNARK) protocol, which enables verifiable emissions reporting mechanisms across a chain of energy suppliers, cloud data centres, cloud services providers, and customers, without any company needing to disclose commercially sensitive information. This allows customers of cloud services to accurately account for the emissions generated by their activities, improving data quality for their own regulatory reporting. Cloud services providers would also be held accountable for producing accurate carbon emissions data.