Ask ten people what "GHG" stands for and most will get it right: greenhouse gas. Ask them how it's actually measured, and you'll usually get a shrug. That gap is a problem, because under CSRD and a handful of other frameworks, measuring emissions is no longer optional for a huge swath of European companies.

Where the Rules Come From

Almost every corporate carbon report you'll ever read traces back to one document: the GHG Protocol, put together by the World Resources Institute and the World Business Council for Sustainable Development back in 2001. It's not a law, but it might as well be, since regulators, auditors, and rating agencies all build on top of it.

Six Gases, One Number

Climate change isn't caused by CO₂ alone. Companies are expected to account for six gases in total: carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulphur hexafluoride. Since these gases trap heat at wildly different rates, they all get converted into a single common unit (CO₂ equivalent, or CO₂e) using something called Global Warming Potential. It's how a report can compare a leaking refrigerant to a diesel generator on the same scale.

The Math Behind It

Strip away the jargon and the calculation is refreshingly basic:

Activity Data × Emission Factor = GHG Emissions (CO₂e)

So if you used 100,000 kWh of electricity, and the grid factor is 0.3 kg CO₂e per kWh, you've emitted 30 tonnes of CO₂e. Multiply that pattern across fuel, freight, flights, and everything else a business consumes, and you start to see the whole footprint take shape.

Five Principles Worth Remembering

The Protocol leans on five principles (relevance, completeness, consistency, transparency, and accuracy), and they're not just box-ticking language. They're what separates a credible inventory from a guess dressed up in spreadsheets. An auditor checking your numbers is essentially checking them against these five ideas.

Getting emissions accounting right is tedious work when it's done by hand: pulling utility bills, chasing down fuel receipts, and cross-referencing factor databases. It's exactly the kind of process that benefits from automation, which is a big part of why we built BUME the way we did: to apply these principles consistently, at scale, without the manual grind.