Carbon accounting: what it is and how it actually works

The word accounting is doing real work in that definition. A carbon footprint is not a survey answer; it is a set of postings. Each posting takes a business record (an invoice line, a meter reading, a fuel receipt), applies a documented emission factor, and lands in a classified ledger under a GHG Protocol scope and, for value-chain emissions, one of the 15 Scope 3 categories.

Everything is expressed in CO2-equivalent (CO2e), which converts the warming effect of other gases (methane, N2O, refrigerants) into one comparable unit. The rulebook is the GHG Protocol: the Corporate Standard for Scopes 1 and 2, and the Corporate Value Chain Standard for Scope 3. Disclosure regimes (CSRD's ESRS E1, IFRS S2, California SB 253) all build on that foundation, which is why the standards questions on our carbon accounting standards FAQ have stable answers.

Step 3 is the expensive one: thousands of lines, each needing a judgment call. It is also the step that decides whether the final number is defensible, which is why modern carbon accounting software concentrates there: AI drafts the classification with a confidence per line, a human reviews, and the evidence link survives. Whether you need software at all, or a consultant, is an honest question with an honest answer in our post on carbon accounting services vs software.