Scope 1 emissions explained: what counts, how to measure, how to reduce

Scope 1 emissions are the direct greenhouse gas emissions from sources that are owned or controlled by an organisation. Under the GHG Protocol, Scope 1 is the first and most tightly defined of the three emission scopes — and the one over which companies have the most direct control.

What counts as Scope 1

Scope 1 is divided into four sub-categories:

• Stationary combustion — natural gas boilers, diesel generators, on-site CHP.
• Mobile combustion — company-owned or leased vehicles, forklifts, aircraft, ships.
• Process emissions — chemical reactions in production (e.g. CO₂ released from limestone in cement manufacture).
• Fugitive emissions — refrigerant leaks from HVAC systems, methane leaks from pipelines, SF₆ from switchgear.

If the company owns or has operational control, the source is Scope 1 — even if it is at a leased facility.

How to measure Scope 1

The methodology is straightforward when data is available:

Emissions (tCO₂e) = Activity data × Emission factor

• Activity data — litres of diesel, m³ of natural gas, kg of refrigerant recharged.
• Emission factor — published by DEFRA, EPA, IEA or national inventory bodies. Convert to CO₂e using the current IPCC Global Warming Potentials.

Best practice is to source activity data from meters, fuel invoices and refrigerant service logs — not from estimates.

Common measurement mistakes

• Missing refrigerants. Refrigerant leakage from HVAC and cold storage is often invisible in accounting but material in emissions terms — HFC-410A has a GWP of ~2,088.
• Using outdated emission factors. DEFRA and national bodies publish annual updates. Using a 2019 factor in 2026 introduces bias.
• Confusing scopes for company vehicles. A company-owned car is Scope 1. An employee-owned car used for business is Scope 3.

Where Scope 1 typically comes from

• Manufacturing — process heat, gas boilers, on-site combustion.
• Logistics — diesel from owned fleet.
• Real estate — gas heating, backup generators, refrigerants.
• Financial services — usually a small share; mostly HVAC and any company vehicles.

How to reduce Scope 1

The credible reduction levers are well established:

1. Electrification of heat — replace gas boilers with heat pumps.
2. Fleet electrification — EV replacement for owned light and medium vehicles.
3. Fuel switching — biomethane, HVO, hydrogen where electrification is not yet viable.
4. Process efficiency — heat recovery, insulation, control system upgrades.
5. Refrigerant management — leak detection, transition to low-GWP alternatives (R-32, CO₂ systems, ammonia).

Every material Scope 1 source belongs on a marginal abatement cost curve (MACC) so investment decisions can be prioritised by cost per tCO₂e avoided.

Financing Scope 1 reductions

Scope 1 reduction projects — heat pumps, fleet electrification, retrofits — are usually eligible for Green Loans under the GLP energy efficiency and clean transport categories. For enterprise-wide programmes, a Sustainability-Linked Loan with a Scope 1 KPI is often the better fit.

Reporting requirements

Scope 1 disclosure is mandatory under CSRD/ESRS E1, SEC climate rules, ISSB IFRS S2, SBTi target-setting and PCAF financed emissions calculations. It must be reported both in absolute terms and, where available, on an intensity basis, and broken down by GHG (CO₂, CH₄, N₂O, HFCs, PFCs, SF₆, NF₃).