A step-by-step guide to starting your Scope 3 emissions journey

Scope 3 covers the indirect emissions across a company's entire value chain, from purchased goods and services to product use and end-of-life disposal. For most organisations it is by far the largest part of the carbon footprint, and the hardest to measure. This guide breaks the work into manageable steps so you can start your Scope 3 journey with confidence.

Why Scope 3 matters

When companies first measure their footprint, they usually begin with Scope 1 and Scope 2: emissions from direct operations and from purchased electricity. But the bulk of the impact normally sits in Scope 3. According to CDP, supply-chain (Scope 3) emissions are, on average, many times greater than a company's direct operational emissions, and across sectors Scope 3 typically represents around three quarters of the total footprint, rising to almost 100% in sectors such as financial services.

Ignoring these upstream and downstream effects means:

1. Underestimating risk: climate impacts in your supply chain can cause disruption and reputational damage.
2. Missing opportunities: cutting Scope 3 can open new markets and strengthen customer relationships.
3. Falling behind: regulators and investors increasingly expect value-chain disclosure. Including Scope 3 also moves from voluntary to mandatory under Spain's Royal Decree 214/2025 from the 2028 calculation onwards.

Step 1: map your value chain

Start by identifying your key business activities, from raw material extraction to product disposal. The GHG Protocol divides Scope 3 into 15 categories (for example, purchased goods and services, business travel, transportation and distribution, use of sold products and end-of-life treatment). Our guide to the 15 Scope 3 categories of the GHG Protocol explains each one. Focus on the categories most relevant to your business.

Step 2: gather preliminary data

Once you have mapped your value chain, collect data from suppliers, partners and internal departments. Lean on existing records such as purchase data or waste logs. Improve data quality by:

• Defining clear metrics for consistency across the organisation.
• Using technology to centralise and standardise data collection rather than relying on scattered spreadsheets.

Step 3: prioritise hotspots

Scope 3 can feel overwhelming, so pinpoint the biggest emitters first. Tools such as life cycle assessment or supplier surveys help. A food manufacturer, for instance, might find that sourcing agricultural raw materials accounts for most of its footprint, making farm-level action the priority. Focus on what is material to your overall impact.

Step 4: engage stakeholders

Reducing Scope 3 usually means working with external partners. Engage suppliers, logistics providers and even end users around shared goals. This might include:

• Supplier codes of conduct: encouraging greener practices or lower-carbon materials.
• Incentive programmes: rewarding suppliers that actively cut their footprints.

Supplier data is the single biggest barrier in Scope 3, and increasingly companies use technology to close the gap. See how AI helps overcome the supplier data barrier.

Step 5: implement reduction strategies

Depending on the hotspots you identify, you might pursue:

1. Lower-carbon raw materials: moving to recycled or certified inputs.
2. Ecodesign: redesigning products for efficiency, lower waste or longevity.
3. Efficient logistics: consolidating shipments or optimising routes.
4. Customer engagement: helping end users reduce emissions in the use and disposal phases.

Step 6: track, report and refine

Build a transparent system to monitor Scope 3 reductions over time, through periodic audits, internal checkpoints and dashboards. Fold the results into a structured carbon footprint reduction plan and keep stakeholders informed of progress.

Overcoming common pitfalls

• Unreliable data: start small, gather data gradually and improve quality over time.
• Supplier pushback: highlight the business case, such as cost savings or access to premium contracts.
• Limited resources: if budget or expertise is tight, focus first on one or two major Scope 3 sources.

A glimpse into the future

Scope 3 will only grow in importance as regulators move towards mandatory value-chain disclosure. Organisations that get ahead of the curve secure a competitive advantage; those that delay risk losing investor confidence and facing higher operational and reputational costs.

Starting your Scope 3 journey can feel daunting, but breaking it into steps makes it achievable: map your value chain, gather data, identify hotspots, engage stakeholders and continuously refine. To put real numbers behind each step, you can rely on Manglai's carbon footprint software.