Reviewing Calculation Methods

To wrap up, let’s review how organizations select and apply calculation methods as part of their Scope 3 decarbonization efforts. As discussed throughout this module, higher-quality activity data generally supports more accurate emissions calculations, while proxy data tends to produce less precise estimates. Having multiple calculation methods available allows organizations to use readily available data today while improving data quality and methodologies over time.

One of the most accessible data points for many organizations is spend-based data. For example, when estimating emissions from employee travel, an organization may have access to flight receipts or expense records. While spend-based methods are easy to implement and useful for establishing a baseline, they involve important tradeoffs.

Spend-based methods are typically less precise and provide limited visibility into the drivers of emissions. As a result, they can make it more difficult to identify, attribute, and track emissions reductions over time—particularly when reductions are driven by operational changes rather than reduced spending.

More activity-based approaches, such as distance-based, fuel-based (where fuel data is available), or supplier-specific methods, provide greater flexibility and insight. These methods enable organizations to capture emissions changes resulting from actions such as switching suppliers, improving efficiency, or changing operational practices, rather than relying solely on changes in spending.

By progressively adopting more granular calculation methods where feasible, organizations can improve the accuracy of their Scope 3 inventories and generate more actionable insights to support decarbonization strategies.