Walmart's Project Gigaton: How to Report Your Emissions as a Supplier

If you supply Walmart, or want to, Project Gigaton is the climate programme worth understanding. Taking part is voluntary, but it is how Walmart engages its suppliers on emissions, and reporting well can pay off. Do it properly and there is public recognition, and, for suppliers in Walmart's supply chain finance programme, better financing rates. Do it loosely and you either leave credit on the table or submit figures that get discounted or removed.

This guide covers what Project Gigaton is, who reports and when, the six pillars you can report against, how reductions are counted, the rules that catch most suppliers out, how to earn recognition, and why it's worth doing. 

What is Project Gigaton?

Walmart is the world's largest retailer, working with over 100,000 suppliers worldwide. Most of a retailer's carbon footprint comes from the production of the goods it sells rather than from running its own stores and depots, so Walmart's biggest lever on climate is its supply chain. 

Project Gigaton, launched in 2017, is how it pulls that lever. Its aim is to work with suppliers to reduce, avoid or sequester one billion metric tonnes (a gigaton) of greenhouse gas emissions across product value chains by 2030. Alongside it runs a nature goal, delivered with the Walmart Foundation, to protect, restore or more sustainably manage 50 million acres of land and one million square miles of ocean by the same date. 

Project Gigaton is the Scope 3 part of Walmart's wider science-based target, set in 2016. That target also commits Walmart to cutting its own Scope 1 and 2 emissions by 35% by 2025 and 65% by 2030, on the way to zero operational emissions by 2040. Walmart did not build the methodology alone. Its science and review sit with a steering committee that includes CDP, the Environmental Defense Fund and the World Wildlife Fund. 

In February 2024, Walmart announced that suppliers had reported projects expected to exceed the one billion metric ton mark, six years ahead of the 2030 goal, with more than 5,900 suppliers signed up since launch. Hitting the target has not ended the programme. Walmart has kept Project Gigaton running, with a growing emphasis on the quality of what suppliers disclose. 

Who can report to Project Gigaton?

Only Walmart's direct (Tier 1) suppliers can take part in Project Gigaton, but they can be based anywhere in the world, and you can report projects wherever they happen, not just in the US. If that is you, a few practical points shape how you report:

• You report once a year. The reporting cycle runs each autumn, typically September to November.
• You report a 12-month period. Most suppliers use their latest full year of data, whether that is a calendar year, a financial year, or another convenient 12 months. Keep the same period each year to avoid gaps or overlaps. You can submit up to two years of data in a single cycle if you are catching up.
• You register through the Walmart Sustainability Hub, then report against whichever pillars fit your business, either in your Project Gigaton Account or through CDP. 
• You can report reductions from across your whole organisation, not only the share of your operations tied to Walmart. Reductions made before you became a Walmart supplier cannot be counted.

What are the Project Gigaton pillars?

Project Gigaton organises reductions into six pillars, plus a seventh "Enterprise Level" catch-all for anything that does not fit neatly.

You do not report against all of them. Most suppliers pick the pillars where they can make real change. 

What emissions data do you need for Project Gigaton?

Project Gigaton runs on activity data, not spend. Rather than estimating emissions from how much you spent, you report what you actually did: kilowatt-hours saved, tonnes of recycled material used, miles taken out of your transport network, units of a more efficient product sold. A spend figure cannot show whether a real reduction happened, which is why the programme does not accept one.

Where the emissions-factor work sits then depends on how you report:

• Through the Project Gigaton calculators, you enter the activity data for each pillar and Walmart applies its own published conversion factors to work out the reduction. Those factors come from recognised sources, for example the EDF Green Freight Handbook for transport, ReFED for date labelling, EPA WARM for waste, USDA models for agriculture, and ENERGY STAR thresholds for product baselines. You supply the activity, Walmart converts it.
• Through CDP, it works the other way round. You report the CO2e saving for each activity yourself, along with the activity type, the scope it affects, and the project's estimated lifetime. Walmart then applies the lifetime multiplier and your stated contribution. So with CDP, you own the calculation and the methodology behind it.

Both routes are counted in full. The only figure that is discounted is a finished CO2e total you calculate and submit directly, which we come to below. Either way, every number has to trace back to real activity data, so it pays to build on solid, well-evidenced figures rather than rough estimates.

How does Project Gigaton count emissions reductions?

This is where Project Gigaton works differently from a normal carbon footprint, and it is worth understanding before you report.

When you cut emissions, Walmart counts it in one of three ways. It treats all three the same, so a tonne saved is a tonne saved whichever type it is.

Absolute reductions. This is the one most people picture when they think about cutting carbon. Your own emissions genuinely go down from one year to the next. For example, you move your factory onto a renewable electricity contract, and your total emissions this year come out lower than last year. The reduction shows up directly in your own footprint.

Avoided emissions. These are emissions that would have happened, but did not, because of something you did. You compare what actually happened against what would have happened if you had carried on as normal (the "business as usual" baseline) and count the difference. The important thing is that these savings often sit outside your own footprint entirely. Say you redesign a product to use less electricity. Every customer who then uses it at home burns less power over the product's life than they would have with the old version. You never emitted those tonnes yourself, but your design change stopped them, so Project Gigaton credits them to you.

Sequestered emissions. Instead of stopping emissions, you remove carbon that is already in the atmosphere and lock it away. Planting trees is the obvious example, or farming in a way that helps soil hold more carbon.

Why this matters for your reporting

Your official carbon footprint, the kind measured under the GHG Protocol (the global rulebook for carbon accounting), mainly counts absolute reductions in the emissions you are responsible for. Project Gigaton goes wider. It also counts avoided emissions, and reductions that happen outside Walmart's own supply chain. Walmart is upfront that this means the programme does not follow the GHG Protocol's Scope 3 rules.

So the tonnes you report to Project Gigaton will not match the numbers in your official carbon footprint, and they are not meant to. One is a measure of the good your projects have done. The other is a formal account of your own emissions. Both are useful, but they answer different questions, so it helps to keep them separate in your reporting and not assume a figure from one belongs in the other.

The rules that keep the totals credible

Miss these and your data can be trimmed or removed when Walmart reviews it:

• Count each project once. A longer-lived project, like a major energy upgrade that keeps saving power for years, is counted over its expected lifetime in the year you carried it out, using a set multiplier. You do not then re-report the same project in later years.
• Do not count the same saving in two pillars. If a change could sit in more than one pillar, pick the best fit and report it there only.
• Expect Walmart to be cautious. In places it deliberately trims the numbers to avoid over-counting. Avoided deforestation, for instance, is only credited over a 20-year window. This stops the same tonne being counted twice by suppliers whose supply chains overlap.

How do you report through CDP?

Walmart's preferred route is disclosure through CDP. Walmart runs this through CDP's Supply Chain programme, and each year CDP sends its Climate Change Questionnaire to selected suppliers on Walmart's behalf. Your reported reduction activities are then mapped into the relevant Project Gigaton pillars, so if you already disclose to CDP, this saves you reporting twice. If you are new to it, our guide to CDP Supply Chain reporting walks through how the programme works for suppliers.

The alternative is Walmart's own Project Gigaton Account, where you either enter activity data into Walmart's calculators or submit an aggregate CO2e figure you have worked out yourself. You should not report the same activity through both CDP and the Project Gigaton Account.

What is the 20% aggregate discount?

Here is the rule that quietly costs suppliers credit. Instead of entering your activity data and letting Walmart do the sums, you can skip that step and just tell Walmart the final tonnes of CO2e you have saved, a single figure you have worked out yourself. If you report that way, Walmart cuts it by 20% before counting it.

The reason is trust. When you use the calculators or report through CDP, Walmart can see how the number was reached and check it. When you hand over a finished total, it cannot see the workings behind it, so it knocks off a fifth to account for the uncertainty.

The takeaway is simple. Wherever you can, enter your activity data into the calculators, or report through CDP using a method that has been independently checked. Both avoid the discount and stand up better to review.

How do you report to Project Gigaton correctly?

Pulling that together, a clean submission tends to follow the same pattern:

• Start from a full-scope footprint. Even though Project Gigaton is project-based, a full Scope 1, 2 and 3 footprint gives you the activity data and baselines the pillars need, and it is increasingly expected for recognition (more on that below).
• Favour activity data over aggregate figures. Report kWh, tonnes, miles and units into the calculators rather than a lump-sum CO2e number, and sidestep the 20% discount.
• Use credible methods and keep your workings. Walmart runs a quality-control review that flags outliers and duplication, with a team of experts signing off on the final data, so document how each figure was produced.
• Report each project once, in the right pillar, in the year it happened.
• Prefer the CDP route where you already disclose, so third-party-assessed data flows straight through.

What are the Project Gigaton recognition tiers, and how do you earn them?

Reporting is not only about helping Walmart hit a number. It feeds a recognition programme that carries commercial weight. There are two supplier statuses:

• Sparking Change, the entry tier. Broadly, you set SMART goals in at least three pillars (or a science-based target) and report progress in at least three pillars.
• Giga Guru, the top tier. Broadly, you set SMART goals across at least three pillars or a science-based target, report progress in each, complete a carbon footprint, and share it with Walmart.

Two things are worth knowing. First, the bar moves. Walmart has raised the Giga Guru criteria more than once and has started asking suppliers to report their full operational emissions footprint, not just project results. It has been clear this is a recognition of climate leadership, not a participation award. Second, because the exact criteria change year to year, check the current requirements on the Walmart Sustainability Hub before you plan around them.

Why put in the effort? A few reasons that go beyond goodwill:

• Procurement standing. Walmart increasingly factors reporting and disclosure quality into procurement decisions, and non-reporting or inadequate reporting can affect contract renewal. Strong reporting supports your position when contracts come up.
• Recognition you can use. Both statuses are published on Walmart's supplier pages. In FY2023, more than 750 suppliers earned Sparking Change and more than 1,100 earned Giga Guru.
• Access to finance. Walmart runs a supply chain finance programme with HSBC that offers improved financing terms to suppliers who show progress in Project Gigaton, including through their CDP scores. It has been a real incentive to report well. 

How Seedling helps

Most of the work behind a strong Project Gigaton submission is carbon accounting. A defensible footprint, solid activity data, credible reduction figures, and clean disclosure. That is what we do.

Seedling pairs carbon accounting software with one-to-one support from a dedicated carbon expert. For Walmart suppliers, that means we can:

• Measure a full-scope footprint (Scopes 1, 2 and 3), giving you the activity data and baselines the pillars draw on, plus the operational footprint recognition now expects.
• Collect data from your own suppliers. Where a pillar depends on information from further down your supply chain, our supplier engagement tool lets you request emissions data that feeds straight into your footprint. 
• Set SBTi-aligned Net Zero targets and build a data-backed plan to reduce emissions, the target-setting that underpins both recognition tiers.
• Support your CDP disclosure, so third-party-assessed data can flow straight into Project Gigaton.
• Keep your data reusable, so the same footprint serves Walmart, your other customers, and your own reporting.

We work with mid-market businesses across the UK, US, Canada and beyond, and we are careful about the difference between what Project Gigaton counts and what your GHG Protocol footprint reports, so you can be confident in both.

To talk it through with the team, you can book a demo, or leave us a message here. We would love to hear from you.

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