Five Common Gaps We Find in First-Time GHG Inventories

Every organisation building its first greenhouse gas inventory believes it has captured the full picture. Almost none actually have, on the first pass, and that is entirely normal. A first-time inventory is as much a data discovery exercise as a calculation exercise. Here are the five gaps we see most often, and why each one tends to hide in plain sight.

1. Scope 3 is scoped too narrowly, too early

The most common gap by far is treating Scope 3 as a short list of obvious categories, usually business travel and maybe waste, rather than systematically working through all 15 categories defined under the Greenhouse Gas Protocol’s Corporate Value Chain standard. For most organisations, the categories that actually dominate a Scope 3 footprint are the ones least likely to be considered first: purchased goods and services, and, for manufacturers in particular, the use of sold products once they leave the factory. A first-time inventory that stops at travel and waste is not incomplete by a small margin. It is often missing the majority of the organisation’s actual footprint.

2. Operational boundaries do not match legal or financial boundaries

Organisations frequently default to reporting emissions for whatever entity happens to hold the accounting records, without explicitly deciding whether the inventory boundary should follow operational control, financial control, or an equity share approach. This matters enormously for organisations with joint ventures, leased facilities, or a mix of owned and managed sites. A site under your operational control but owned by another party may need to be included in full, even if it never appears on your balance sheet, while a minority equity stake in a separate entity may need only a proportional share included. Getting this wrong does not just produce an inaccurate number, it produces an inventory that cannot be meaningfully compared year on year once the boundary decision is eventually corrected.

3. Scope 2 electricity is measured on only one basis

As covered in detail elsewhere, Scope 2 emissions can be calculated on a location basis or a market basis, and they answer different questions. First-time inventories very often calculate only one, usually whichever is simpler given the data on hand, without recognising that a mandatory disclosure obligation, or a sophisticated customer, may specifically require the other, or both. Discovering this gap during an assurance process, rather than during initial data collection, is a considerably more expensive place to find it.

4. Data quality and primary versus secondary sources are not tracked

It is common for a first-time inventory to arrive at a final number without a clear record of which figures came from actual metered or invoiced data, and which came from industry-average emission factors used to fill a gap. This is understandable under time pressure, but it creates two problems. First, it makes the inventory very difficult to defend under scrutiny, since nobody can say with confidence which parts of the total are highly reliable and which are rough estimates. Second, it makes year-on-year comparison unreliable, because a change in the total emissions figure might reflect a genuine change in the business, or it might simply reflect a data source that was replaced with a better one. Tracking data provenance from the outset, even informally, pays for itself the moment anyone asks how confident the organisation is in its own number.

5. Emission factors and gas coverage are out of date or inconsistent

Emission factors, the figures used to convert activity data like litres of fuel or kilowatt hours of electricity into greenhouse gas emissions, are updated periodically as underlying science and grid compositions change. First-time inventories frequently combine emission factors from different vintages, different sources, or different geographic scopes without realising the inconsistency, simply because whatever factor was easiest to find was used at the time. Similarly, some early-stage inventories inadvertently omit certain greenhouse gases beyond carbon dioxide, such as methane or nitrous oxide, particularly in sectors like agriculture, waste, or industrial processes where these gases can represent a material share of total emissions on a carbon dioxide equivalent basis.

Why these gaps matter more than they used to

None of these gaps are unusual for a first attempt, and none of them reflect poorly on the team doing the work. What has changed is the cost of leaving them unaddressed. A voluntary inventory with a rough Scope 3 estimate and inconsistent emission factors was, until recently, a reasonable starting point. An inventory feeding into a mandatory climate disclosure, an NGER submission, or a major customer’s own Scope 3 reporting is now expected to withstand genuine scrutiny, and gaps like these are exactly what an external assurance provider, or an increasingly carbon-literate customer, will find first.