Tackling Scope 3: how Proximus manages 4,000+ suppliers

We spoke with Catherine Bals, Group Sustainability Lead at Proximus, for a new episode of Tapio Talks.

After years of environmental initiatives, Proximus has sharpened its ambition: to reach net zero across the value chain by 2040 and create a circular blueprint by 2030. Catherine’s team stewards this transformation, from target setting to governance and reporting.

Here’s what we learned from our conversation with her.

From a list of projects to a company-wide transition plan

When Catherine Bals joined the sustainability team in 2020, Proximus’ strategy was still in its early stages: a spreadsheet filled with actions and potential projects.

The first step in making sustainability more concrete and impactful was to understand the company’s footprint. Proximus measured its carbon emissions and conducted a first materiality assessment, mapping actions to where they matter most. That analysis became the foundation of a climate transition plan owned across the group and supported at the management level.

Although CSRD gave direction and a framework, Proximus committed to reducing its impact regardless of regulatory pressure. As Catherine puts it, “Legislation like CSRD helps, but the point isn’t compliance for its own sake. It’s using the framework to steer real transformation.”

How Proximus handles 4,000+ suppliers

Like many large organisations, Proximus’ biggest challenge is scope 3. Devices, infrastructure, and supplier manufacturing significantly impact the company’s footprint, and Proximus doesn’t control its suppliers’ roadmaps. However, Catherine and the rest of the team were able to find levers to promote change.

Signing the Supplier Code of Conduct

All Proximus suppliers must sign the Supplier Code of Conduct, which embeds environmental, social, and governance standards, including waste, emissions, circularity, human rights, and business ethics, into their agreements with the company. This includes requirements to measure and report CO₂ emissions across scopes 1, 2, and 3, set science-based emission reduction targets, and adopt circular design and renewable-energy practices. 

Mapping out and segmenting suppliers

Proximus mapped its 4,000+ suppliers and decided to focus on around 150 that drive most emissions. These 150 suppliers were then segmented by maturity:

• suppliers with targets and programmes already in place
• high-impact suppliers without targets yet, but influenceable – these are supported closely by Proximus, for example, to set science-based targets and report annually on their impact
• hard-to-influence suppliers are addressed via industry initiatives, with the option to revisit relationships if progress stalls

Organising industry initiatives

Industry initiatives are very interesting for the third segment of suppliers, because Proximus is getting other competitors to be allies. Proximus works with peer operators internationally and in Belgium to align requests with standard suppliers. “Decarbonisation shouldn’t be a competitive arena. By collaborating, we amplify our voice and accelerate action without touching competitive positioning,” Catherine says.

Governance that sticks: leadership, ownership, incentives

Catherine is clear: “You won’t shift a company without your CEO and board on board.” With executive sponsorship secured, Proximus translated its plan into clear domains of action.

Ownership involves line teams, networks, product, procurement, and HR, while the central team steers ambition, coherence, and performance. Accountability is embedded in the system: leaders and employees include environmental objectives in their incentives.

Resistance is inevitable. “The bottleneck is often caused by some managers’ competing priorities and different ways of measuring performance. This can sometimes create friction,” Catherine notes. The solution is gradually aligning objectives and keeping moving.

Conclusion with tips from Catherine

Catherine’s advice for sustainability leaders starting out:

• learn continuously and stay curious
• focus on impact, not just reporting
• don’t get discouraged by resistance — progress is step by step
• make sure leadership is engaged and accountability is clear

For Proximus, this approach turns an ambitious net zero target into a structured transformation plan that extends across its value chain and into its 4,000+ suppliers.