Build Your First Carbon Baseline

Why a first baseline is different from every inventory after it

Your first carbon baseline sets the reference point every future year is compared against. It does not need to be perfect — it needs to be documented well enough that a reasonable person can understand what was included, what was estimated, and why.

1. Define your organizational boundary

Decide which entities, facilities, and operations are covered, and pick a consolidation approach (operational control, financial control, or equity share). Record this decision — it rarely changes year to year, and an undocumented boundary is the most common reason a later reviewer cannot reproduce a baseline.

2. Identify your emissions sources

Walk through Scope 1 (fuel, vehicles, refrigerants, on-site processes), Scope 2 (purchased electricity, steam, heating, cooling), and Scope 3 (everything else in the value chain — start by screening categories for relevance rather than trying to calculate all fifteen at once).

3. Collect the business data you already have

Most of a first baseline comes from records that already exist: utility bills, fuel invoices, expense reports, and procurement exports. Assign an owner for each data type before chasing the data itself — ownership gaps are what stall a first baseline more than data gaps do.

4. Select calculation methods and factors

Match each activity to an appropriate emission factor by geography, year, and unit. Where a precise method is not yet possible, a documented spend-based estimate is a legitimate starting point — the goal is transparency, not false precision.

5. Document your estimates and exclusions

Every assumption, proxy, and exclusion should be written down with a reason. This single habit is what separates a defensible first baseline from a number nobody can explain twelve months later.

6. Assemble the baseline report

Bring the boundary, methodology, activity data, factors, and documented estimates together into one internally reviewed report. That report — not just the final number — is your actual baseline.