Well-to-tank (WTT) emissions are the upstream greenhouse gas emissions associated with extracting, processing, refining, and transporting a fuel or energy carrier before it reaches the point of use. They are sometimes called upstream or cradle-to-gate fuel emissions.
WTT emissions sit alongside tank-to-wheel (or combustion) emissions, which are released when the fuel is actually burned. Together they make up the full well-to-wheel footprint of a fuel.
Why it matters
Under the GHG Protocol, the combustion (tank-to-wheel) part of fuel use sits in Scope 1 (for fuels burned by the company) or Scope 2 (for purchased electricity). The WTT portion is reported separately under Scope 3 Category 3, Fuel- and Energy-Related Activities Not Included in Scope 1 or 2.
Including WTT meaningfully improves the completeness of a footprint. For diesel, for example, WTT emissions add roughly 20% on top of the combustion emissions; for grid electricity, WTT plus T&D losses can add 8–10%.
A practical example
If a company burns 10,000 litres of diesel in its fleet, the combustion emissions (Scope 1) might be ~25 tCO₂e using the DESNZ tank-to-wheel factor. Applying the corresponding WTT factor adds roughly another ~5 tCO₂e, reported under Scope 3 Category 3, for a more complete picture of the fuel's true footprint.
We always include WTT in every engagement that reports Scope 1 or 2. See the full approach on the methodology page.