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Most companies with climate goals already have a decarbonization plan in place. Many have set ambitious targets, joined initiatives like the Science Based Targets initiative (SBTi), and are actively working to reduce their Scope 1 and 2 emissions. These efforts are critical and commendable but often overlook a major piece of the puzzle – suppliers.

On average, 80% of a company’s emissions fall under Scope 3, the indirect emissions that occur throughout the value chain. Despite their significance, supplier-related emissions remain one of the least developed and most fragmented areas of the decarbonization journey. Without meaningful supplier engagement, even the most well-designed climate strategies risk falling short of their goals.

In this guide, we’ll explore why supplier engagement has been so difficult to tackle, what’s at stake if it continues to be overlooked, and how companies that get it right can turn it into a source of competitive advantage.

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Understanding Scope 3: The Supplier Emissions Challenge

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To understand why supplier engagement matters, we need to first talk about Scope 3 emissions. Scope 3 encompasses all indirect emissions that occur in a company’s value chain: everything from raw materials and transportation to employee commuting, product use, and supplier operations. For most companies, Scope 3 emissions account for the vast majority of their total emissions.  

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The challenge? You can’t reduce what you can’t measure. And measuring Scope 3 emissions means asking your suppliers for data, often across dozens of categories and potentially thousands of facilities.

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To report on these data points, suppliers need support. Many still rely on manual processes or aren’t collecting emissions data at all. And even when they are, the formats, quality, and completeness of their data vary widely. This process can be frustrating for both companies and their suppliers. It also undermines efforts towards reporting accuracy, decarbonization strategy, and progress toward climate targets. 

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Why Supplier Engagement Gets Overlooked

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Engaging suppliers takes time and coordination. It’s messy. It doesn’t scale well with manual tools. And in a world focused on quick wins, companies tend to deprioritize the harder (but more meaningful) work of building supplier relationships.

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Most sustainability teams are also already overextended. They’re juggling disclosure requirements, internal buy-in, and data aggregation. Building trusted supplier relationships often feels like a “nice to have” — not a must-have.

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There’s also a mindset gap. Many organizations treat climate data as a one-way street —something to extract from vendors rather than co-create. The result? Missed opportunities, rising frustration on both sides, and a broken link in the decarbonization chain.

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What’s at Stake: The Cost of Disengaged Suppliers

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When suppliers aren’t meaningfully engaged in climate work, companies face more than just data gaps. The ripple effects impact credibility, competitiveness, and climate performance.

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1. Inaccurate or Incomplete Emissions Data

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You can’t make smart decisions without reliable information. Relying on generic emissions factors instead of supplier-specific data means you're modeling on assumptions. That makes it harder to identify hotspots, prioritize action, or track real progress.

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2. Missed or Inaccurate Disclosures

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From CDP to CSRD and CA SB253, reporting frameworks are evolving fast. 

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Regulators and investors are demanding more granular, auditable emissions data — including Scope 3. If supplier data is incomplete or outdated, you risk underreporting, overreporting, or general non-compliance.

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3. Weakened Climate Credibility

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Public targets are only as strong as the data behind them. If Scope 3 reporting is vague or hand-waved away, stakeholders may question the company’s commitment. That perception gap can erode trust with investors, customers, and even employees.

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4. Procurement Disadvantages

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Major buyers are starting to screen vendors based on climate data. If your business is part of someone else’s supply chain — and you can’t provide complete, high-quality emissions data — you may lose contracts to more transparent competitors.

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5. Lost Innovation and Collaboration

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Suppliers are often closest to the source of emissions. When you don’t include them in your climate strategy, you lose access to ideas, efficiencies, and solutions that could accelerate your progress.

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In short: disengaged suppliers don’t just delay your decarbonization plan — they compromise it.

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From Compliance to Collaboration

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Suppliers are more than risks to manage – they’re partners in progress. By bringing them into the fold early and often, you build a more resilient, transparent, and future-proof supply chain. You unlock new value. And you move from reactive compliance to proactive climate leadership.

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What Effective Engagement Looks Like

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The good news is that supplier engagement doesn’t have to be hard.

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Effective supplier engagement starts with clarity and consistency — and it’s powered by the right tools and approach.

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Here’s what it looks like in practice:

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1. Simple, Actionable Requests

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Instead of sending complex spreadsheets, provide guided data requests tailored to your supplier’s industry and capacity. Focus on high-impact categories first such as purchased goods, transportation, or energy use.

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2. Education and Support

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Offer onboarding resources, templates, FAQs, and office hours. Work with companies like Green Project that can provide tailored education sessions and webinars and work directly with your suppliers. 

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Empower suppliers to participate, don’t just pressure them to comply.

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Read our case study: How Green Project Enabled NotReal to Meet Microsoft’s Supplier Requirements

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3. Feedback and Transparency

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Suppliers want to know where they stand. Show them how their data contributes to your goals. Share benchmarked reports or dashboards. Create a sense of partnership — not just paperwork.

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4. Prioritize Your Top Emitters

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You don’t have to start with everyone. Use a materiality approach: focus on the vendors that contribute the most to your emissions or make up the largest portion of your spend. ‍

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Watch our recent webinar: Scaling Net Zero: Supplier Engagement Strategies That Work

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5. Leverage Smart Tools

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Green Project’s act50 is a digital marketplace and supplier engagement engine designed to bring every supplier — regardless of size, region, or climate maturity — into the clean energy transition.

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It tackles one of the most difficult parts of Scope 3 action: enabling renewable energy procurement across your supply chain.

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With act50, you can:

• Engage suppliers at scale through a centralized digital platform
• Connect them with affordable, instantly-transactable renewable energy certificates (EACs) from ACT Group’s global inventory
• Enable audit-grade, RE100-compliant proof of clean energy use
• Track, validate, and report on supplier emissions reductions with transparency and confidence

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The platform integrates into your existing workflows and complements carbon accounting efforts by embedding action into engagement, offering suppliers both the infrastructure and access they need to decarbonize.

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What makes act50 especially powerful is that it unlocks renewable energy purchasing for suppliers who may have never had access before. For many, this is their first opportunity to buy clean energy in a traceable, verifiable way and it directly reduces your Scope 3 emissions.

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Whether you’re looking to kickstart supplier action or scale an existing program across regions and categories, act50 makes it easy to move from intention to impact and to do it in a way that’s equitable, efficient, and built for long-term success.

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Ready to Engage Smarter?

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Green Project helps companies like yours bridge the Scope 3 gap. With act50, we make supplier engagement manageable, measurable, and meaningful so decarbonization can be a shared journey, not a solo effort. 

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