Scenario-based case study: low-carbon ammonia

This case study uses a hypothetical food and agriculture supply chain scenario to explore how market instruments can be used to account for low-carbon ammonia used in fertilizer. Developed by WBCSD in collaboration with Carbon Trust, with input from participating member companies, it reflects the practical sourcing decisions companies face today. All figures are illustrative.

The worked example shows how the gap between physical and market-based reporting differs under each approach, and why. The case study also sets out what remains open under current standards, including certificate governance and residual emission factors, and what this means for making credible claims as the standards landscape evolves.

Through this case study, readers can:

• Understand why book-and-claim is the primary route in this scenario, where physical traceability is lost at two points: between producer and farm, and between farm and buyer
• See the narrower conditions under which mass balance allocation can be credible, such as a defined and traceable cooperative or supply-shed pool
• Use a worked example of both approaches to inform claims across long, fragmented agricultural value chains