A practical overview of primary and secondary data for carbon accounting

This article provides an overview of how primary and secondary data plays a role in Scope 1, 2, and 3 emissions reporting, while offering guidance on where to focus your efforts in order to maximize impact.

Primary or secondary data… What’s the difference?

Primary data originates directly from your operations or supply chain and is typically the most precise option. Examples include on-site fuel use or supplier-specific emissions factors.

This data definitely enhances precision, transparency, and the ability to benchmark operational changes, but there is a caveat. It often comes with higher costs and a need for rigorous verification to ensure quality​​.

Secondary data on the other hand relies on industry averages, estimates, and published data sources. It is cost-effective and accessible, but can fall short in capturing the nuances of your business operations, potentially limiting the granularity of your carbon reduction strategies​​.

Consider the following example:

An industrial company buys steel from two different suppliers and needs to report its GHG emissions.

As you can see, the emissions that each of these suppliers produce is likely vastly different. While the same average-based secondary data emission factor from DEFRA might appear to apply to both of them, there’s a good chance Supplier B is producing far more GHG.

Does that mean you should avoid secondary data like the plague? No, but it is important to know which data is the best for each scope and its categories.

Choosing the right data for each scope

The balance between primary and secondary data varies between the different emissions’ Scopes:

Scope 1: Direct emissions

Primary data is critical here as you are taking direct measurements of things like fuel consumption and heating for your buildings.

Secondary data may only supplement gaps where direct measurement is impractical, such as using industry emission factors for fugitive emissions​​.

Scope 2: Indirect emissions from purchased energy

A mix of primary and secondary data will be needed when reporting both location-based and market-based emissions.

Primary data may include specific energy consumption invoices while secondary data can then be used in the absence of detailed contracts or when reporting residual emissions.

Scope 3: Value chain emissions

This is the most complex category, where secondary data frequently dominates due to the sheer breadth of value chain activities.

However, integrating supplier-specific primary data, especially for purchased goods or transportation, significantly enhances accuracy​​. But if you want a comprehensive understanding of what counts as primary vs secondary data across all three scopes, we’ve put together an exhaustive list in the following guide.

Balancing precision and feasibility

Striking the right balance between primary and secondary data is both an art and a science. Over-reliance on secondary data can erode the credibility of your reporting, while exclusively using primary data may be resource-intensive and impractical. The best approach is a hybrid one, focusing primary data collection on material hotspots while using secondary data to provide broader coverage. For example:

Secondary data supplementation: Downstream Scope 3 categories like consumer use of sold products, where collecting direct data may not be feasible​​.

Primary data focus: Critical suppliers with high GHG impacts or direct operational emissions (Scopes 1 and 2).

Common pitfalls and how to avoid them

1. Overestimating data precision: Secondary data is inherently less accurate, and using it without transparency can undermine stakeholder trust. Always disclose the percentage of emissions calculated using secondary data, particularly for Scope 3.
2. Failing to engage suppliers: Many Scope 3 hotspots, such as purchased goods or inbound logistics, require supplier collaboration to gather meaningful primary data.

Practical tips for enhanced carbon accounting

Focus on hotspots: Prioritize collecting primary data for emission sources that significantly contribute to your carbon footprint.

Standardize data quality checks: Whether using primary or secondary data, ensure accuracy by implementing rigorous validation processes.

Invest in automation tools: Carbon accounting software, like Position Green’s dedicated solution, can help streamline data collection and improve audit readiness.

Conclusion

By mastering the complexities of primary and secondary data, businesses can produce transparent, credible GHG inventories that enhance stakeholder confidence and align with long-term environmental goals.

But in case you missed it above, we highly recommend downloading our practical resource on carbon accounting data types. It offers deeper insights into balancing precision and feasibility, with real-world examples tailored to Scope 1, 2, and 3 emissions.