Why carbon accounting outgrows the spreadsheet

Nearly every mining operation starts its carbon accounting in a spreadsheet, and for a while that is the right decision. It is fast, everyone can read it, and the first inventory is mostly a data-gathering exercise anyway.

The trouble starts later, and it is not really about scale. It’s that emissions data behaves differently from the financial data spreadsheets were designed around.

Four ways emissions data breaks the model

Emission factors change after the fact. A tonne of diesel burned last March is a fixed physical event, but the factor you multiply it by is not. Factors get revised, regional grids get re-baselined, and methodologies get updated. In a ledger, last year’s numbers are settled. In a carbon inventory, last year’s numbers move — and you need to be able to say exactly why.

Restatement is normal, not an error. When a factor changes or a site corrects a meter reading, the right answer is to restate the baseline and keep both versions. A spreadsheet usually handles this by someone saving inventory_2025_v7_FINAL_revised.xlsx. The number changes; the reason it changed lives in somebody’s memory.

The boundary keeps moving. Acquire a site, divest a pit, change an equity share, and the organisational boundary shifts. Every historical total has to be recalculated on the new boundary to stay comparable — a full rebuild of the model each time.

Scope 3 is not yours to control. Most of a mining operation’s footprint sits upstream and downstream: purchased goods, transport, processing of sold product. That data arrives in different units, on different schedules, at wildly different quality, from parties with no obligation to be consistent. A spreadsheet can hold it. It cannot tell you how much of it you should believe.

The real problem is provenance, not arithmetic

The calculations themselves are not difficult. Activity data times emission factor, aggregated up a hierarchy. A competent analyst can build that in a day.

What’s hard is answering the questions that follow:

• Where did this activity figure come from, and who approved it?
• Which version of which factor was applied, and when did it change?
• Why is this quarter different from the same quarter last year — real reduction, or a methodology change?
• Which numbers are metered, which are invoiced, and which are estimated?

Those are provenance questions. A spreadsheet stores values; it does not store how a value came to exist. And as soon as the inventory is assured, or feeds a public target, provenance is the thing you are actually being asked for.

The symptoms of having outgrown it

It’s rarely a dramatic failure. It looks like:

• The reporting cycle takes weeks, and most of that is chasing and reconciling, not analysing.
• Two people produce different totals from the same source data.
• Nobody can reproduce last year’s published figure from this year’s workbook.
• The assurance provider’s questions take longer to answer than the inventory took to build.
• A single analyst is the only person who understands the model.

That last one is the one that should worry an executive most. If the inventory lives in one person’s head, the organisation’s climate disclosure does too.

What to put in place first

You don’t need to replace everything at once. In order of value:

1. Separate activity data from factors. Keep the physical measurements — litres, tonnes, kilowatt-hours — in their own layer, and apply factors as a versioned lookup. Then a factor revision is a re-run, not a rebuild.
2. Version the methodology, not just the file. Record which factor set and which boundary produced each published figure, so a restatement can be explained rather than defended.
3. Grade your data. Mark every input as metered, invoiced, or estimated. This single habit tells you where accuracy is worth buying and gives assurance providers what they ask for.
4. Make recalculation cheap. If restating three years of history on a new boundary is a week of work, it won’t happen, and comparability quietly degrades.

Why it matters beyond compliance

Decarbonisation decisions are capital decisions — electrifying a haul fleet, changing a power contract, redesigning a process. Those need a defensible baseline, a credible forecast, and the ability to show the effect of a change against a moving regulatory background.

A spreadsheet can report what happened. Deciding what to do next needs something that can hold its own history — and explain it.

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Carbomine is a decarbonisation and carbon accounting platform built for the mining industry. Learn more at carbomine.net.