Net-zero greenhouse gas mitigation potential across multi-tier supply chains

Attainment of corporate net-zero goals will depend on sufficient mitigation of scope 3 emissions, but implementation is challenged by measurement and management complexities. Here, we investigate the multi-tier greenhouse gas emissions structures of supply chains to assess mitigation potential using environmentally extended input-output models. We find that 56–70% of scope 3 emissions included in current science-based coverage guidance occur within the operational emissions of the first two tiers of supply. To meet net-zero objectives, companies will typically need to reach deep into tiers 4 or 5 of supply, where traceability has proven impractical. Although the two-tier system is insufficient for net-zero, it could be a near-term strategy with potential benefits of reducing disclosure costs and improving data quality, ultimately increasing scope 3 adoption. Our study highlights opportunities for phased scope 3 coverage provisions in emerging policy, and the allowance of high-quality tradable market mechanisms to aggregate deep mitigation efforts. Implementation of net-zero GHG emissions targets increasingly requires the mitigation of indirect (scope 3) emissions created in companies’ untraceable upstream supply chains, according to an investigation of emissions structures across geographies and tiers of supply.