Enterprise ESG platforms have transformed corporate emissions reporting. They consolidate data from finance, procurement and operations, and produce audit-ready disclosures aligned to CSRD, ISSB, SBTi and CDP.

For Scope 1 and Scope 2 — the data inside the business — they work well. Scope 3 is where things get harder.

The long tail problem

For most organisations, 70–90% of total emissions sit in the value chain — and the further down the supply chain you go, the smaller suppliers tend to be.

Tier 1 and Tier 2 suppliers are usually enterprise-ready. They have ESG teams, data, and the ability to plug into a supplier portal. The long tail is different. In the UK alone there are around 5.5 million SMEs, accounting for roughly 37% of the country's greenhouse gas emissions (British Business Bank). This isn't a marginal slice of Scope 3 — it's where most of it lives.

And it is dominated by businesses that are time-poor and resource-light. Only 15% of UK SMEs have measured their carbon footprint, just 26% feel they have the knowledge to engage with net zero, and only 14% feel they have the time (FSB). Asking them to log into a supplier portal and complete a Scope 3 questionnaire is, at best, optimistic.

How Zellar works

Zellar sits alongside the enterprise stack rather than inside it. It works in three parts — one to start the journey, one for the supply chain owner, and one for the SME.

1. Snapshot. An online tool — built in plain language SMEs actually understand — that captures their emissions baseline in minutes, using automated energy reads, any data they already have, and trusted industry proxies to fill the gaps. This is the front door. Once the snapshot is complete, the SME has a baseline and the corporate has data.

2. Dashboard. A system of record for the corporate's SME ecosystem. The dashboard aggregates the results of every supplier snapshot into a single, live view of supply chain emissions — coverage, hot spots, progress, and where to focus next. The enterprise platform stays as the system of record for Tier 1 and Tier 2; Zellar's dashboard is the equivalent for everyone beyond that. Together, they cover the whole value chain.

3. Zellar Coach. For the SME, the journey doesn't stop at the snapshot. Coach turns the baseline into a living record of their sustainability progress — pick it up next year exactly where it was left, or keep it live throughout the year. No re-keying, no starting from scratch. It's also their emissions credentials, ready to be shared with the next customer that asks: answer once, reuse many times. And Coach doesn't just record — it coaches, guiding the SME through practical actions to lower their emissions and their bills. As individual SMEs reduce their footprint, those reductions flow up into the corporate dashboard, which means the corporate's supply chain emissions come down too.

That's the Zellar infinity loop: snapshot → dashboard → coach → improvement → dashboard. Every part feeds the next.

Same problem, different challenges

So back to the question. Zellar is not trying to replace the enterprise ESG platform. It’s solving the same problem — but tackling a very different challenge within it.

The enterprise platform is the corporate's source of truth: the place where Scope 1, 2 and 3 data is consolidated, audited and reported externally. It needs to be enterprise-grade, with the controls, integrations and assurance trail to support regulatory disclosure.

Zellar is the engagement layer that makes the SME Scope 3 piece of that platform credible. It captures supplier data at source, in a format SMEs can actually complete, and produces standardised, structured emissions data the corporate can drop straight into its enterprise system. The corporate gets better data faster. The SME gets a tool that helps their own business, not just their customer's reporting.

That matters more than it might first sound. Most Scope 3 programmes are held back by three things: low supplier engagement, incomplete coverage of the long tail, and poor data quality where engagement does happen. Where SMEs don't engage, corporates fall back on spend-based estimates — and research suggests those estimates can overstate emissions by 60–80%. The result is a Scope 3 number that is less a measurement than an educated guess. Zellar tackles all three: it lifts engagement, extends coverage, and replaces estimates with primary data.

From a one-way ask to a two-way relationship

Zellar sits between the corporate's supplier portal and the SME — the bridge that turns a one-way data request into a two-way relationship. Today, most supplier portals are extractive: the corporate asks for data, and the SME (maybe) sends it back. Nothing flows the other way. The supplier gets no insight, no benefit, and no reason to do it again next year.

With Zellar in the middle, that changes. The SME submits their data once, but they get something back in return: a report of their own footprint; a coach pointing them at practical actions that lower bills and improve efficiency; and a digital emissions record they can nurture and share with the next customer that asks — without re-keying anything.

For the corporate, the data the SME captures comes out in a consistent, structured format that feeds straight into the enterprise system — no spreadsheets to chase, no email chains. Both sides have a reason to keep using the system year after year.

The bigger picture

Enterprise platforms have solved the corporate side of emissions reporting. The next frontier is the value chain — and the value chain is mostly small businesses. That can't be solved by building a bigger enterprise tool. It needs a platform designed for SMEs.

That's the gap Zellar fills, and why it complements rather than competes with the enterprise stack. Together, they give organisations a credible way to engage the entire value chain, all the way down.