Well-to-Tank (WTT)
Well-to-tank (WTT) emissions are the upstream greenhouse gases associated with extracting, refining, processing, and transporting a fuel or energy source from its point of origin to the point of use. They represent the supply chain emissions of the fuel itself, before it is consumed.
What is Well-to-Tank (WTT)?
Well-to-tank (WTT) emissions capture the greenhouse gases produced throughout the supply chain of a fuel — from extraction at the wellhead, mine, or source, through refining, processing, and distribution, to delivery at the point of use (the "tank"). These emissions are distinct from the emissions produced when the fuel is actually burned (tank-to-wheel or point-of-use emissions).
For fossil fuels, WTT emissions cover the energy used in drilling and extraction, transportation of crude oil or gas by pipeline and tanker, refining processes, blending, storage, and distribution to forecourts or consumers. For electricity, the WTT equivalent covers the upstream emissions from fuel extraction and processing for the power station. For biofuels, WTT covers agriculture, harvesting, processing, and transportation of the feedstock.
The DEFRA emission factor dataset includes WTT factors for all major fuel types alongside the direct combustion factors. For example, diesel has a direct combustion factor of approximately 2.51 kgCO₂e per litre plus a WTT factor of approximately 0.62 kgCO₂e per litre — meaning the upstream supply chain adds roughly 25% to the total lifecycle emissions of diesel. Similarly, UK grid electricity has both a generation factor (Scope 2) and a WTT factor (Scope 3) that accounts for the upstream emissions of the fuels used in power stations.
Under the GHG Protocol, WTT emissions are classified as Scope 3 Category 3: "Fuel- and energy-related activities not included in Scope 1 or Scope 2." This category captures: WTT emissions of fuels consumed in Scope 1 sources, WTT emissions of fuels used to generate Scope 2 electricity, and transmission and distribution (T&D) losses for purchased electricity.
WTT emissions are often overlooked in early-stage carbon accounting but can be material. For organisations with high fuel consumption (transport, logistics, construction), WTT adds a significant layer to the total footprint. Including WTT is required under the Carbon Reduction Plan (PPN 06/21) and is increasingly expected in comprehensive Scope 3 reporting.
Practical Examples
A logistics company consuming 500,000 litres of diesel reports 1,255 tCO₂e from combustion (Scope 1) and approximately 310 tCO₂e from WTT (Scope 3 Category 3) — the upstream emissions from extracting, refining, and distributing the diesel.
A company reporting Scope 3 for its electricity consumption includes both the T&D losses and the WTT emissions of the fuels burned at power stations, using the DEFRA WTT factors for UK grid electricity.
A construction firm calculates WTT emissions for the red diesel used in its plant equipment, adding approximately 25% to the direct combustion figure to capture the full lifecycle fuel impact.
How Climatise Helps
Climatise automatically calculates WTT emissions alongside direct combustion figures for all fuel types, using the DEFRA WTT factors. The platform includes WTT in your Scope 3 Category 3 total without requiring separate data entry — it derives the WTT figure from the same fuel data used for Scope 1.
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