Carbon inventories without the jargon: scopes, boundaries and why the process matters

A carbon inventory is simply an organised account of the greenhouse gases your business is responsible for. It sounds straightforward. In practice, the decisions you make along the way shape what the number means, and whether anyone should trust it.

Here’s how I explain it to clients who’d rather be running their factory than reading standards.

Three scopes, one picture

Most inventories follow the Greenhouse Gas Protocol, which splits emissions into three “scopes”:

Scope 1 is what you burn yourself: gas in boilers, diesel in vans and forklifts, process emissions from your own equipment, and refrigerant leaks.
Scope 2 is the electricity (and any purchased heat or steam) you use. It’s usually reported two ways. The location-based figure uses the average grid mix. The market-based figure reflects the contracts you actually hold.
Scope 3 is everything else in your value chain: the materials you buy, freight, business travel, waste, how customers use and dispose of your products. For most manufacturers, this is the biggest slice by far.

Boundaries are where the judgement lives

Before you count anything, you have to decide what you’re counting. Which sites? Which subsidiaries? Do you take an operational-control approach, or count emissions in line with your ownership share? Which Scope 3 categories are material enough to include?

These aren’t technicalities. Two businesses with the same factory can report very different numbers depending on these choices. A good inventory states them openly so a customer, lender or auditor can follow the logic.

Data quality beats false precision

In the first year, you’ll be working with a mix of metered data, invoices, spend-based estimates and industry averages. That’s normal. What matters is being honest about which is which, and improving the weakest data over time.

I’d much rather see a clear baseline with sensible estimates and a plan to firm them up than a number quoted to three decimal places that nobody can explain.

Pick a base year and stick to it

Your first full inventory usually becomes your base year: the point you measure progress from. If your business changes significantly through an acquisition, a site closure or a better method, you recalculate the base year so you’re comparing like with like.

Why the process is the point

This is the part people underestimate. To build an inventory, finance has to talk to operations, operations has to talk to procurement, and procurement has to talk to suppliers. Questions get asked that normally don’t. Where is our energy really going? Which suppliers could we not do without? Which customers are going to ask us for this next?

Those conversations often produce more value than the final figure. They expose waste, highlight supply-chain risks and give your board information it doesn’t usually see. I’ve written more about that in The report is the by-product.

Getting started

You probably already hold most of what you need: energy bills, fuel cards, purchase ledgers, waste transfer notes. Pull together twelve months of those, agree your boundary, and you have the bones of a first inventory. From there it’s about filling gaps and building a method you can repeat each year.

If you’re facing CBAM or customer questionnaires, the same data does double duty. It’s one piece of work that answers several questions at once.