Screening & prioritizing Scope 3 categories: Where to start for maximum impact

If there’s one thing that makes Scope 3 emissions challenging, it’s their scale. For many companies, these indirect emissions from suppliers, transport, product use and even end-of-life treatment can make up 70–90% of the total footprint. With 15 categories defined under the GHG Protocol, the natural question is: where do you start?

The answer lies in screening and prioritisation. Not every category is equally significant, and trying to measure everything at once can lead to wasted effort, patchy data and frustration. A smarter approach is to focus first on the categories with the greatest impact on your business and climate strategy.

Step 1: Do a high-level screening

Start with a quick estimate of each Scope 3 category using spend data, industry averages or input–output models. This won’t give you perfect numbers, but it will highlight where the “big-ticket” items are. For most companies, purchased goods and services, business travel and transportation dominate but every value chain has its own story.

Step 2: Identify material categories

Next, evaluate which categories matter most based on three dimensions:

• Size: Where are the largest emissions likely to be?
• Influence: Where do you actually have the ability to drive reductions?
• Stakeholder relevance: What do regulators, investors or customers expect you to report on?

This helps you distinguish between emissions that are large but hard to control, and those that are both significant and actionable.

Step 3: Go deeper in priority areas

Once you’ve identified your most material categories, move beyond generic databases and seek primary data. That might mean engaging suppliers directly, conducting product life cycle assessments or using sector-specific emission factors. Even improving the quality of just one or two priority categories each year can dramatically strengthen your inventory.

Step 4: Build a roadmap

Screening and prioritisation shouldn’t be a one-off exercise. As your business changes and as better data becomes available your focus should shift too. The best companies treat Scope 3 as a journey: start broad, then get deeper, better and more specific over time.

Key takeaway

You don’t need to tackle all 15 Scope 3 categories at once. Start where the emissions and the opportunities for change are greatest. That’s how you build credibility, focus your resources and make real progress.