Which scope 3 categories are the hardest to measure?

Less than 1 minutemin

4 August 2026

Which scope 3 categories are the hardest to measure?

Measuring scope 3 emissions is one of the most technically demanding tasks in corporate sustainability. Unlike scope 1 and 2 emissions, which sit within a company’s direct control, scope 3 spans the entire value chain, from raw material extraction to how customers eventually dispose of a product. For most organizations, scope 3 accounts for the vast majority of their total carbon footprint, which makes getting it right both critically important and genuinely difficult.

Not all scope 3 categories are created equal, though. Some are relatively straightforward to quantify with existing data. Others are a measurement headache that even experienced teams struggle with. Understanding which scope 3 categories pose the greatest challenges, and why, is the first step toward building a credible measurement approach.

Why scope 3 data is notoriously difficult to collect

The core problem with scope 3 is that most of the emissions happen outside your organization. You’re relying on suppliers, customers, logistics partners, and sometimes end users to either share their data or behave in ways you can anticipate. Neither of those things is guaranteed.

The GHG Protocol divides scope 3 into 15 categories across upstream and downstream activities. Each one requires a different data collection approach, and the quality of available data varies enormously. Primary data, meaning actual figures from your value chain partners, is almost always more accurate than secondary data like industry averages or spend-based estimates. The problem is that primary data is also far harder to obtain. Suppliers may not track their emissions at all, or they may use different methodologies, making comparisons unreliable. Downstream categories introduce even more complexity because you’re essentially trying to model how people outside your organization use and dispose of your products.

Add to that the sheer volume of transactions, products, and relationships most companies manage, and it becomes clear why scope 3 data collection is so resource-intensive.

The scope 3 categories with the greatest measurement challenges

Some categories consistently stand out as the hardest to measure accurately, regardless of industry or company size.

Purchased goods and services (Category 1): This is typically the largest upstream category and one of the hardest to pin down. It requires emissions data from every supplier across your entire procurement spend. Most organizations default to spend-based estimation, which introduces significant uncertainty.
Capital goods (Category 2): Calculating the embedded emissions in machinery, buildings, or equipment requires detailed life cycle data that suppliers rarely provide in a usable format.
Business travel (Category 6): While conceptually simple, this category becomes complex when employees book travel independently, use a mix of providers, or travel internationally where emission factors differ widely.
Employee commuting (Category 7): This one often relies entirely on employee surveys, which are notoriously inconsistent. People forget, estimate, or simply don’t respond, leaving large data gaps.
Use of sold products (Category 11): This requires modeling how customers actually use your products over their lifetime, including energy consumption patterns that vary by geography, usage intensity, and user behavior. For consumer electronics, appliances, or vehicles, this category can dwarf everything else.
End-of-life treatment of sold products (Category 12): Estimating whether products end up in landfill, recycling, or incineration requires assumptions about waste infrastructure that vary significantly by country and region.
Investments (Category 15): Relevant for financial institutions and holding companies, this category requires emissions data from investee companies, many of which don’t disclose it.

What ties these categories together is a common thread: they all depend on data that sits beyond your organizational boundary. Whether it’s a supplier’s manufacturing process, a customer’s usage habits, or an investee’s operations, you’re working with incomplete information and making assumptions to fill the gaps. That’s not a failure of methodology, it’s simply the nature of scope 3. The key is being transparent about where estimates are used and how confident you are in them.

Common data gaps and estimation pitfalls

Even teams with strong processes run into recurring problems when working through their scope 3 inventory. A few patterns come up again and again.

Overreliance on spend-based estimates is probably the most common issue. Spend-based methods use financial data and average emission intensity factors to estimate emissions. They’re easy to apply and cover gaps quickly, but they can be wildly inaccurate for specific suppliers or product categories. Using them across an entire Category 1 inventory without any supplier-level data gives you a number that looks precise on a spreadsheet but has very wide uncertainty bounds in practice.

Another pitfall is inconsistent system boundaries. Companies sometimes include certain suppliers or product lines in one year and exclude them the next, making year-on-year comparisons meaningless. This is particularly common when organizations are still figuring out which entities fall within their reporting scope under frameworks like CSRD.

Double counting is also a real risk, especially in complex supply chains where the same emissions might be attributed to multiple tiers. And at the downstream end, assumptions about product lifetimes and usage patterns are often borrowed from industry averages that may not reflect your actual customer base at all.

How leading organizations are closing the measurement gap

Progress on scope 3 measurement doesn’t happen all at once. The organizations doing it well tend to take an iterative approach, improving data quality category by category over time rather than trying to achieve perfection in the first year.

Supplier engagement is one of the most effective levers available. When companies actively work with key suppliers to collect primary emissions data, it improves accuracy for Category 1 significantly. Some organizations build supplier data requests into procurement processes or use collaborative platforms to standardize how data is shared. Setting SBTi-aligned supplier targets also creates a shared incentive to improve data quality on both sides.

For downstream categories, product-level life cycle assessments (LCAs) are increasingly used to build more accurate use-phase and end-of-life models. LCA specialists bring a specific methodology to this work that goes well beyond generic emission factors, and the results can meaningfully change how a company understands its total footprint.

Many organizations also invest in better internal data infrastructure. Connecting procurement systems, travel booking tools, and financial data to a centralized emissions platform reduces manual work and improves consistency. It won’t solve the supplier data problem overnight, but it does create a more reliable foundation for year-on-year tracking.

When to bring in a scope 3 specialist

There’s a point in most scope 3 measurement journeys where internal capacity hits its limit. That might be when a company is preparing its first full value chain inventory, when existing estimates are being challenged by stakeholders or auditors, or when regulatory requirements like CSRD are raising the bar on what “good enough” actually means.

It’s worth being specific here, because scope 3 measurement draws on several distinct areas of expertise. A scope 3 emissions reduction consultant approaches the problem differently from an LCA specialist, who in turn works differently from a CSRD reporting expert focused on disclosure requirements. The right kind of help depends on what stage you’re at and what your specific challenge is. Someone building a Category 11 model for a consumer product company needs different skills than someone designing a supplier engagement program for a manufacturing business.

External specialists are particularly useful when the work requires deep technical knowledge that isn’t worth building in-house for a defined project, or when an independent perspective adds credibility to your reported figures. They can also help organizations move faster, which matters when reporting deadlines are fixed and the internal team is already stretched.

Ready to make scope 3 measurement less daunting?

Scope 3 is genuinely hard, but it doesn’t have to be a blocker. With the right expertise on your side, even the most complex categories become workable. At Dazzle, we match organizations with pre-screened scope 3 specialists who know this territory inside out, whether you need an LCA expert, a supplier engagement lead, or someone to help you prepare for CSRD reporting requirements.

Our network of 300+ sustainability professionals is available on a project or interim basis, so you get exactly the support you need without overcommitting. And because we hand-pick matches based on your specific challenge, you’re not just getting a generalist. You’re getting someone who has done this work before. Reach out to our team and you could be working with the right expert within 48 hours.

Looking for hands-on support with this? See how our Scope 3 consultants help companies build inventories that hold up to scrutiny.