Understanding Scope 1 Emissions: Direct Combustion Sources

Scope 1 emissions represent the greenhouse gases released directly from sources that a company owns or controls. These are often the most straightforward emissions to measure, yet many organizations struggle with comprehensive identification and accurate quantification. This guide walks through the major categories of Scope 1 emissions and the methodologies used to calculate them under the GHG Protocol Corporate Standard.

Stationary Combustion

Stationary combustion is typically the largest source of Scope 1 emissions for most businesses. This category includes all fuel burned in equipment at fixed locations such as boilers, furnaces, generators, and heaters. To calculate emissions from stationary combustion, companies must track the type and quantity of each fuel consumed. The GHG Protocol provides default emission factors for common fuels including natural gas, diesel, liquefied petroleum gas, and fuel oil. The basic calculation multiplies the quantity of fuel consumed by the appropriate emission factor to yield tonnes of CO2 equivalent. For natural gas, the emission factor is approximately 56.1 kg CO2 per gigajoule of energy content. Companies should use fuel purchase records, meter readings, or supplier invoices as the basis for activity data, and should apply country-specific or supplier-specific emission factors where available for greater accuracy.

Mobile Combustion

Mobile combustion covers emissions from vehicles and mobile equipment owned or controlled by the company. This includes cars, trucks, forklifts, construction equipment, and any other fuel-burning transport assets. The calculation can be performed using either a fuel-based method, which multiplies fuel consumption by emission factors, or a distance-based method, which uses kilometers driven and vehicle-specific emission factors. The fuel-based approach is generally more accurate and is recommended where fuel consumption data is available. Companies with large vehicle fleets should implement fuel tracking systems, either through fuel card programs or telematics solutions, to ensure comprehensive data capture. Leased vehicles should be included in Scope 1 if the company has operational control, which is typically the case for long-term leases.

Process Emissions

Process emissions arise from industrial processes other than combustion. These are particularly significant in sectors such as cement manufacturing where the calcination of limestone releases CO2, aluminum smelting where the reduction process generates perfluorocarbons, and chemical production where various reactions release greenhouse gases. Calculating process emissions requires sector-specific methodologies, and companies should refer to the relevant IPCC guidelines or industry-specific protocols. For example, cement producers use clinker production data and the calcium oxide content of raw materials to estimate process CO2 emissions. These calculations can be complex, and companies in emissions-intensive industries should consider engaging specialist consultants for initial baseline assessments.

Fugitive Emissions

Fugitive emissions are unintentional releases of greenhouse gases from equipment leaks, maintenance activities, or system failures. The most common sources include refrigerant leaks from air conditioning and cooling systems, methane leaks from natural gas distribution equipment, and SF6 leaks from electrical switchgear. Refrigerant emissions are calculated by tracking the quantity of refrigerant added to systems during maintenance and servicing, a method known as the mass balance approach. Given that many refrigerants have global warming potentials thousands of times greater than CO2, even small leaks can represent significant emissions. Companies should maintain detailed refrigerant management logs and implement regular leak detection programs to both reduce emissions and cut costs associated with refrigerant replacement.

Best Practices for Scope 1 Reporting

Accurate Scope 1 reporting requires systematic data collection processes, clear organizational boundaries, and consistent application of emission factors. Companies should establish an internal carbon accounting policy that specifies the consolidation approach, whether equity share or operational control, and documents all data sources and calculation methodologies. Annual reconciliation of fuel purchase records against metered consumption helps identify data gaps or errors. Where direct measurement is available, such as continuous emissions monitoring systems in industrial facilities, measured data should take precedence over calculated estimates. Building robust Scope 1 measurement capabilities is the foundation for credible carbon reporting and provides the baseline against which reduction targets can be tracked.