The hidden uncertainty behind emissions data produced by British supermarkets
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British supermarkets publish Scope 3 carbon totals that include emissions from producing and transporting the products they sell. Those can mix suppliers’ records with estimates based on industry averages. The UK’s new climate reporting standard asks companies to explain their data, but does not require a percentage showing how much comes from supplier-specific primary data. Aruneem Mazumder and Rishikesh Sinha explain the gap, show how other countries handle it and propose two fixes.
Almost all of a supermarket’s carbon footprint sits outside its own stores and lorries. It lies in the farms, factories and transport behind what it sells. Reporting rules call these value chain emissions Scope 3. Scope 1 is what a company emits itself, such as diesel in its lorries and gas in its store boilers. Scope 2 is the electricity, heat or cooling it buys. Scope 3 is the rest of the chain, from farms and factories to the customer’s kitchen.
Tesco, the country’s largest supermarket chain, reports that close to 99 percent of its emissions are Scope 3. Within purchased goods and services, the largest part, 9 percent of the calculation uses primary data, meaning records from suppliers themselves, such as their fuel or fertiliser use. Much of the rest is estimated from spending, by multiplying what the retailer paid by an average carbon figure for that type of product. Estimated that way, negotiating a lower supplier price can make reported carbon fall even if nothing becomes cleaner. Switching to a genuinely lower-carbon supplier at the same price may show no improvement at all.[1]
The difficulty is what those totals contain. SRS S2 , the UK’s new climate reporting standard tells companies to prefer measured data, supplier data and verified data . Yet a single published figure can blend all of these with industry averages, which the standard treats as an acceptable basis. Tesco discloses how much of its inventory rests on primary data. The disclosures by Sainsbury’s and Lidl GB reviewed here publish no comparable figure. A retailer that is open about its data can therefore look weaker than one that says nothing.[2]
The same rulebook makes asset managers publish a precise percentage for their financed emissions. For companies such as supermarkets it asks for an explanation of the data used , but no percentage. On 30 September 2026 the Financial Conduct Authority (FCA) published its final disclosure rules . Listed companies must apply them, or explain why not, for accounting periods beginning on or after 1 January 2027, with first reports in 2028 and an extra year’s relief for Scope 3. A company that reports its Scope 3 emissions still need not publish a percentage showing what the number is made of. That is the gap.[2][3]
Behind the number
Three weaknesses sit behind a Scope 3 total. This is about what each retailer discloses, not how much it emits.
The first is where the data comes from. Of the three retailers compared here, only Tesco reports 9 percent primary data in purchased goods and services . Sainsbury’s, the second largest, says it has begun integrating primary data from strategic suppliers , without giving a figure. Current public climate reporting of Lidl GB, the British arm of Lidl, the fifth largest , provides no equivalent.[1][4][5]
The second is timeliness. Tesco combines 2025/26 Scope 1 and 2 data for its own operations with mostly 2024/25 Scope 3 data for its supply chain, so one headline may not describe a single year.[1]
The third is checking. The accounting firm Deloitte provided independent limited assurance over selected Tesco Scope 3 categories totalling 15.7 million tonnes carbon emission against a reported footprint across all three scopes of 68.1 million. The checking therefore covers selected categories, not the whole Scope 3 inventory.
Beyond reporting
Supplier emissions figures, whatever their quality, can inform supplier onboarding, evaluation, contract renewal and switching decisions. The metric can therefore reward bargaining rather than decarbonisation.
Sainsbury’s reports 51.6 percent of its Scope 3 emissions covered by suppliers with approved science-based targets . That indicates commitment, not the quality of inventory data.[4]
Uncertain data can then fail in two directions. It may be over-weighted, lending an estimate false authority, or discounted so that cost and reliability dominate. Both are rational responses to unlabelled data.
The accountability gap
Retailers set Scope 3 targets for emissions they neither produce nor directly observe. Who is responsible for producing reliable data and who pays for it?
The standard does not resolve that tension. It presumes Scope 3 can be estimated reliably using secondary data and industry averages, while asking only that readers can understand how much rests on primary and verified inputs. Responsibility for emissions should not collapse into responsibility for the number.[2]
This problem is not unique to Britain. The UK standard adopts an international template that around 40 jurisdictions are implementing . Australia , one of them, uses the same wording. Japan’s newly mandatory sustainability disclosure regime shields companies from misstatement liability on Scope 3 estimates only where they document their assumptions, methodology and internal procedures, thus answering a neighbouring question through liability.[6][7][8]
Policy proposals
First, make companies show the mix. For purchased goods and services, companies should publish what share of their emissions figure rests on their suppliers’ own data and set out which calculation methods produced the rest, including where the two are combined. For an investor, it makes two retailers easier to compare. For a supplier, it reveals where better evidence is genuinely needed.
Shoppers will not meet these numbers at the till. They are company-wide figures, published in annual and sustainability reports and they do not tell a shopper the footprint of a single item. The few environmental labels on food sold in Britain are voluntary and separately assessed. What the figures do underpin is the credibility of a supermarket’s climate promises, which the Competition and Markets Authority’s Green Claims Code says must rest on solid evidence.[9]
The principle already exists. The GHG Protocol’s Scope 3 Standard has required conforming companies since 2011 to disclose, for each category, the percentage calculated using supplier data. The British standard did not carry that requirement across. The Department for Business and Trade could add the percentage to the UK standard itself, or the FCA could add it later through its listing rules.[10]
The EU’s original sustainability reporting standards required exactly this figure. The revised standards adopted in July 2026, for use from 2027, do not keep it. The precedent shows the disclosure is workable. Its removal shows why a proportionate version matters. Our solution asks for one figure, not a long list.[11]
Lidl shows the two systems side by side. It belongs to Germany’s Schwarz Group , whose European businesses report under EU rules that can require supply-chain emissions. Lidl GB is a private British company outside the FCA’s regime. UK law makes it report its own energy use and emissions, plus some business travel, but not the full supply-chain inventory discussed here.[12][13]
No retailer can start everywhere at once. Sainsbury’s singles out 27 high environmental impact agricultural suppliers . Yet the headline total does not tell a reader which parts rest on supplier records and which on estimates.[4]
A proportionate rule need not force small suppliers to calculate full footprints. Farms can provide fuel, fertiliser or livestock data for intermediaries to convert. Dunbia, which supplies both Tesco and Lidl GB , already works to a Scope 3 intensity target covering on-farm emissions. Spend-based estimation can remain where better evidence is unavailable. The requirement is to show where each method sits. A percentage can still hide how much of the supplier base it represents, so future disclosure should pair emissions coverage with supplier coverage.[14][15]
Second, ask suppliers once. A farm or food manufacturer selling to several supermarkets can currently face several different carbon questionnaires. Sainsbury’s uses Foodsteps, Secaro and HIGG . Lidl GB works with Mondra and with Manufacture 2030 , which now trades as Secaro. Tesco has left Secaro.[4][15]
The cost of answering repeatedly falls on suppliers and the EU has legislated against exactly that , giving suppliers with no more than 1,000 employees the right to refuse requests beyond a defined standard. Co-ordination in Britain could cut the repetition. It would not give suppliers a legal right to say no, as the EU does.[16][17]
The British Retail Consortium already identifies the absence of a standardised supplier-data methodology as a barrier. The government should build on the BRC-Mondra Coalition , a group of retailers and suppliers including Tesco, M&S, Ocado and Asda that is developing a shared way of measuring product carbon footprints, rather than create another system. Aldi, Lidl GB, Asda, Morrisons and the Co-op are not listed in London, so the FCA’s rules do not reach them, even though they buy from the same suppliers. The government’s Modernising Corporate Reporting programme, its wider review of what companies must report, should consider how equivalent requirements can reach large private retailers.[18]
Clearer figures and simpler reporting
T his analysis draws on published disclosures rather than observed procurement practice. But British grocery retail does not lack Scope 3 numbers. It lacks a consistent way of knowing what those numbers rest on. The fix is modest. Show where supplier evidence ends and estimation begins, then use a common request so suppliers provide the evidence once rather than repeatedly. Numerical precision should no longer be mistaken for measurement quality.
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