Conduct Your First Carbon Footprint Assessment in an SME: Scopes 1, 2 and 3 Step by Step

Quick answer. A carbon footprint measures the greenhouse gas (GHG) emissions an SME generates directly (scope 1: heating, vehicles) or indirectly (scope 2: purchased electricity; scope 3: purchases, transport, business travel). The method rests on collecting consumption data (energy, fuel, purchases) and applying official ADEME emission factors, expressed in tCO2e (tonnes CO2 equivalent). For an SME, scope 3 often represents 80 to 90% of emissions. A first assessment identifies the largest sources and sets a quantified action plan.

A carbon footprint is not yet mandatory for every SME. The regulatory obligation — the greenhouse gas emissions assessment (BEGES), set out in article L.229-25 of the French Environmental Code — applies to companies with more than 500 employees (250 in the overseas territories) every four years, plus certain public bodies. Since the reform that took effect in 2023, these mandatory assessments include significant indirect emissions (scope 3).

For SMEs below those thresholds, the absence of an obligation does not mean the absence of pressure. Sustainability reporting obligations (CSRD) target large companies, which pass the demand down their value chain: a major client, a bank or an investor increasingly asks suppliers to measure their footprint. Some public grants are also conditional on a reduction effort. Acting early is therefore as much a competitive advantage as a precaution.

A carbon footprint starts by clarifying organizational and operational boundaries.

Financial or operational consolidation#

• Financial: include entities over which you have financial control (subsidiaries, majority stakes).
• Operational: include the sites and activities you control in practice, regardless of legal structure.

Non-listed SMEs often favour operational consolidation, which is simpler and more relevant for steering reduction actions.

Reference year and frequency#

Choose a calendar year (e.g. 2025) as the reference and set a reporting rhythm (annual or biennial). This consistency lets you track the trajectory over time.

The GHG Protocol, the international standard adopted by ADEME's Bilan Carbone® method, sorts emissions into three complementary scopes.

Scope 1: direct emissions#

Scope 1 covers emissions from sources you own or directly control.

Scope 2: indirect energy-related emissions#

Scope 2 measures emissions generated when producing the energy you buy and consume.

The electricity emission factor varies greatly by national energy mix. In France it is low (around 0.060 tCO2e/MWh) thanks to nuclear power, against roughly 0.350 tCO2e/MWh in Germany and more in Poland.

Scope 3: other indirect emissions#

Scope 3 covers emissions upstream and downstream of the value chain. For an SME, it is usually the majority of the footprint (80 to 90%).

Scope 3 is often estimated from proxy data (purchase amounts, material weights), since direct measurement of every supplier is rarely available.

1. Map emission sources#

List all consumption items: energy (gas, oil, electricity, steam), fuel, upstream purchases, upstream and downstream transport, business travel, waste, water. This map shows where to focus first.

2. Gather consumption data#

Collect, for the reference year:

• Scope 1: gas, oil, propane invoices (kWh, m³ or litres), fuel consumption, refrigerant refill records.
• Scope 2: electricity invoices (kWh), network heat or cold invoices.
• Scope 3: purchase amounts by category, travel mileage, transport invoices, waste tonnage.

3. Apply ADEME emission factors#

ADEME's Base Empreinte® (formerly Base Carbone®) provides tens of thousands of factors to convert each consumption into tCO2e. For reference (verify in the database, updated yearly):

Factors depend on the energy source, the region (for electricity) and the transport mode. ADEME's Base Empreinte is the official French reference.

SMEs without detailed data: the estimation approach#

Where fine data is missing, use estimates: energy consumption per m² of premises, average fleet mileage, sector monetary ratios for purchases. A documented estimate beats an omitted source.

Partial or complete scope 3?#

A first iteration can focus on upstream purchases and business travel, often the dominant items, then extend to downstream transport and product end-of-life. The key is to cover significant emissions and document the chosen perimeter.

Regulatory assessment or voluntary effort#

Do not confuse the regulatory BEGES (mandatory perimeter and filing above 500 employees) with the voluntary diagnostic assessment, which follows the same ADEME principles without a publication duty. For an unregulated SME, the voluntary assessment is the right starting point.

• Do not overlook scope 3: limiting yourself to scopes 1 and 2 understates an SME's real footprint by 80 to 90%.
• Trace your data sources: a credible assessment separates measured from estimated data.
• Use up-to-date emission factors: the Base Empreinte changes every year.
• Set a realistic target: a quantified three-year reduction plan beats a distant, unsupported goal.
• Link the assessment to your strategy: it feeds your double materiality analysis and your 2026 ESG obligations.

As a French chartered accountant registered with the Ordre des experts-comptables, we support SMEs on their low-carbon path. Recently, we supported an 80-employee construction SME on its first carbon footprint. The firm assumed its emissions came mostly from its twelve site vehicles. The assessment showed the opposite: nearly two-thirds of emissions were scope 3, chiefly material purchases (steel, concrete, insulation), the rest split between travel and vehicles. This insight reoriented the action plan: instead of an isolated investment in electric trucks, the firm negotiated lower-carbon materials and shorter supply circuits with its suppliers, for a greater effect at lower cost.

The lesson is simple: a carbon footprint is a management tool, not an environmental formality. SMEs that treat it that way find material and energy savings, and position themselves well against clients increasingly attentive to the low-carbon value chain.

Hayot Expertise advice. Launch your assessment this year, even without an obligation. A solid baseline prepares you for client demands, green finance and upcoming sustainability requirements. We proceed in three steps: an initial diagnostic, validation of key data and the reduction plan, then annual monitoring through indicators. Our ESG audit and reporting offering integrates the carbon footprint into a broader CSRD readiness effort and helps you mobilise ecological transition grants. For dedicated accountancy support, let us talk.

• Define the perimeter (financial or operational consolidation)
• Set the reference year and reporting rhythm
• Map consumption items (energy, fuel, purchases, travel, waste)
• Collect primary data (invoices, meters, registers)
• Identify the relevant emission factors in the ADEME Base Empreinte
• Convert each consumption into tCO2e
• Total emissions by scope (1, 2, 3)
• Spot the three to five largest sources
• Set a reduction target and a quantified action plan
• Document assumptions and plan annual monitoring