For most manufacturers, the emissions that matter aren’t the ones they can see. Fuel burned on site and electricity purchased are measurable and usually modest. The large share sits upstream in purchased materials and downstream in distribution and product use — and it belongs to other companies’ operations, which is what makes it difficult.
Where to Concentrate
Scope 3 is defined across many categories, and attempting all of them at once is how these projects stall. For a typical manufacturer, purchased goods and services dominates, often by a wide margin. Upstream and downstream transport, waste, and — for energy-consuming products — use of sold products usually make up most of the remainder.
Start by estimating roughly which categories are material for your business, then measure those properly and estimate the rest. Precision everywhere is neither achievable nor useful.
Two Methods, Different Accuracy
Spend-based calculation multiplies what you spent in a category by a published emissions factor. It’s quick, requires only purchasing data you already have, and gives a rough baseline. Its weakness is that it can’t distinguish between a low-carbon supplier and a high-carbon one — spend the same money and you get the same number, so it can’t show improvement.
Activity-based calculation uses physical quantities — tonnes of steel, kilowatt-hours, tonne-kilometres of freight — multiplied by material-specific factors. More accurate, more work, and it responds to real changes in what you buy and how you ship.
Supplier-specific data is the most accurate tier: actual emissions figures from your suppliers for the products you buy. Availability varies enormously, and it’s realistic to expect it only from larger suppliers initially.
A sensible path is spend-based for a first baseline, then convert your highest-impact categories to activity-based, then pursue supplier-specific data for your largest material flows.
What You Already Hold
More than most manufacturers expect. Purchase quantities by material sit in your procurement records. BOM data tells you material composition per product. Freight records give distances, modes, and weights. Waste transfer documentation gives disposal volumes.
The obstacle usually isn’t missing data — it’s that the data lives in operational systems and has never been aggregated for this purpose. Connecting it is a reporting exercise more than a collection one.
Being Honest About the Numbers
Scope 3 figures carry real uncertainty, particularly when built on generic factors. State the methodology, state the assumptions, and don’t present estimates with more precision than they possess.
Consistency matters more than absolute accuracy in the early years. If your method stays stable, year-on-year movement means something even where the absolute figure is approximate. Changing methodology annually makes trends uninterpretable.
Requirements Are Moving
Disclosure obligations differ by jurisdiction, by company size, and by sector, and they have been changing quickly. Check what currently applies to you rather than working from an assumption — and note that customer requirements often arrive before regulatory ones, particularly if you supply larger businesses with their own reporting obligations.
ticktick.ai aggregates purchase quantities, BOM material content, and freight data into activity-based emissions calculations from records you already maintain.
