When a mid-sized professional services firm set out to tackle its carbon footprint, the leadership team quickly realised something uncomfortable: the emissions from their own offices were almost trivial compared to what sat in their supply chain. Heating the building, running the servers, even the company cars—all of it paled next to the carbon embedded in the services and goods they bought from others.

This is the reality of Scope 3 emissions. For most organisations, particularly those in professional services, somewhere between 70% and 90% of their total carbon footprint comes not from their own operations, but from their suppliers. It's the consultants they subcontract, the IT equipment they lease, the catering for client events, the print runs, the couriers. If you're serious about Net Zero, you simply cannot ignore it.

The Regulatory Pressure

This wasn't just an exercise in corporate conscience. The firm faced mounting pressure from multiple directions. Their larger clients—several of whom were FTSE 100 companies—had begun including carbon disclosure requirements in their supplier questionnaires. The Streamlined Energy and Carbon Reporting (SECR) framework meant they were already publishing their Scope 1 and 2 figures, but Scope 3 was becoming impossible to sidestep.

Beyond that, the Task Force on Climate-related Financial Disclosures (TCFD) recommendations were filtering down through their sector. And with public sector work forming a decent chunk of their revenue, PPN 06/21—the government's procurement policy note requiring carbon reduction plans from major suppliers—made this a commercial imperative, not just an ethical one.

The board had made a public Net Zero commitment. Now they had to deliver on it.

The Problem: No Visibility, No Data

The firm had over 400 active suppliers on their books, ranging from multinational technology providers to one-person consultancies. When the sustainability team started asking for emissions data, the responses were, let's say, mixed.

Some of the larger suppliers had sophisticated carbon reporting and could provide detailed breakdowns. Others sent across PDF brochures with vague statements about "environmental responsibility." A fair number simply didn't reply at all. And a surprising proportion came back with honest confusion: they'd never measured their emissions and had no idea where to start.

The team faced a classic data problem. They needed consistent, comparable figures across a wildly inconsistent supplier base. Chasing individual suppliers via email wasn't going to cut it—they'd tried that for three months and had data from fewer than twenty.

The Approach: Start With What Matters

Rather than boiling the ocean, the firm took a pragmatic approach. They segmented their supplier base by spend and carbon intensity, focusing first on the top 100 suppliers who represented roughly 85% of their procurement expenditure. The logic was straightforward: if you're going to move the needle, start with the suppliers who actually make a difference.

They rolled out a supplier ESG portal—a structured online questionnaire that suppliers could complete at their own pace. The questions were specific but not overwhelming: actual emissions figures if available, energy consumption data, whether they had their own carbon reduction targets, and what initiatives they had in place.

Crucially, for suppliers who didn't have their own emissions data (which turned out to be the majority), the platform offered estimation tools. Based on sector benchmarks, company size, and energy usage proxies, suppliers could generate a reasonable approximation of their carbon footprint. It wasn't perfect, but it was vastly better than nothing—and it gave smaller suppliers a starting point they could refine over time.

The Results: A Baseline to Build From

Within four months, the firm had usable emissions data from 87 of their top 100 suppliers. Not all of it was verified, and some of it was clearly estimated, but for the first time they had a genuine picture of their Scope 3 footprint.

The numbers told a clear story. Twenty suppliers—just 20%—accounted for approximately 70% of the supply chain emissions. These weren't necessarily the biggest suppliers by spend; some were in carbon-intensive sectors like logistics, manufacturing, and print production. One specialist printing company, used for maybe £40,000 a year, had a higher carbon impact than a technology partner billing ten times that amount.

Armed with this insight, the firm could finally have meaningful conversations. They weren't asking suppliers to do the impossible; they were identifying specific areas where reductions would actually matter and working collaboratively on improvement plans.

What Actually Changed

For the top 20 emitters, the firm established quarterly review meetings focused specifically on carbon reduction. Some suppliers rose to the challenge—one logistics provider switched a portion of their fleet to electric vehicles, partly prompted by this engagement. Others committed to renewable energy tariffs or consolidating deliveries to reduce transport emissions.

A handful of suppliers, frankly, weren't interested. In two cases, the firm made the decision to transition spend to alternative providers with stronger environmental credentials. These weren't easy conversations, but they sent a clear signal that sustainability wasn't just a box-ticking exercise.

The data collection also revealed opportunities closer to home. Several high-carbon suppliers were being used by multiple departments without any coordination. Consolidating volumes not only reduced emissions through fewer deliveries but also improved commercial terms.

Lessons for Others

If there's one takeaway from this firm's experience, it's that perfect shouldn't be the enemy of good. Waiting until every supplier can provide verified, audited emissions figures means waiting forever. Estimates and approximations, clearly labelled as such, are a legitimate starting point. The important thing is to get the baseline in place and then improve the data quality over time.

The second lesson is that supplier engagement matters more than supplier demands. The most productive relationships came when the firm approached suppliers as partners in a shared challenge, rather than issuing ultimatums. Many smaller suppliers were genuinely grateful for the guidance and the estimation tools—it helped them answer questions from other clients too.

Finally, integrating carbon tracking into existing procurement processes made a real difference. When ESG data sits in a separate system that nobody checks, it gets ignored. When it's visible alongside commercial performance, quality scores, and contract renewals, it becomes part of normal supplier management.

The firm hasn't achieved carbon neutrality yet—they're realistic about the timeline. But they've gone from having no Scope 3 visibility to having a genuine reduction strategy, tracked month by month, with clear accountability for progress. That's not a bad outcome for twelve months' work.