Greenhouse Gas Reporting for Suppliers: What Your Customers Need and Why

Greenhouse gas reporting requests from customers have shifted from rare to routine for suppliers across industries. If you've received a questionnaire asking for your carbon emissions data, you're experiencing a direct consequence of corporate climate commitments, investor pressure, and emerging regulations requiring companies to measure and reduce their value chain emissions. Understanding what customers need, why they need it, and how to provide it efficiently matters for maintaining strong relationships.

Why Your Customers Need Your Emissions Data

Your emissions are your customer's Scope 3 emissions. The GHG Protocol, which most companies follow, divides emissions into three categories:

Scope 1: Direct emissions from sources the company owns or controls (vehicles, boilers, manufacturing processes)
Scope 2: Indirect emissions from purchased electricity, steam, heating, or cooling
Scope 3: All other indirect emissions in the value chain, including purchased goods and services

When your customer buys products or services from you, the emissions from producing those goods fall into their Scope 3, Category 1 (Purchased Goods and Services). For most companies, Scope 3 represents 60-90% of total emissions, making supplier data critical.

Regulations like the EU Corporate Sustainability Reporting Directive (CSRD) and investor frameworks like CDP now require comprehensive Scope 3 reporting. Your customers can't meet these requirements without data from suppliers. That's why the questionnaires are arriving.

What You Need to Report: Minimum Requirements

At minimum, customers need your Scope 1 and Scope 2 emissions. This represents the direct climate impact of your operations. Some customers request Scope 3 as well, but for most small and mid-sized suppliers, Scope 1 + 2 is the baseline expectation.

Report your annual emissions in metric tons of CO2 equivalent (tCO2e), covering the same calendar or fiscal year your customer specifies. They may ask for absolute emissions (total tCO2e) or emission intensity (tCO2e per unit of revenue or production).

Scope 1 Examples

Emissions from:

Natural gas combustion in boilers or heaters
Diesel or gasoline in company-owned vehicles
Refrigerant leaks from HVAC systems
On-site manufacturing processes (if applicable)

Scope 2 Examples

Emissions from:

Purchased electricity for facilities
Purchased steam or district heating (less common for small suppliers)

If you don't have significant Scope 1 sources (for example, you operate in a rented office with electric heating and no company vehicles), your Scope 1 might be zero or negligible. That's acceptable to report. Focus accuracy on Scope 2, which almost every business has.

How to Collect Activity Data

GHG calculations require activity data (how much energy you used) and emission factors (how much CO2e each unit of energy produces).

Gathering Activity Data

Electricity: Get your annual consumption in kilowatt-hours (kWh) from utility bills. Sum all 12 months or request an annual statement from your provider.

Natural Gas: Bills show consumption in therms, cubic meters, or kWh. Note the units carefully as emission factors vary by unit.

Fuel for Vehicles: Fuel purchase records or fuel card statements show liters or gallons of diesel, gasoline, or other fuels consumed. Alternatively, estimate using mileage and average fuel efficiency, though direct fuel data is more accurate.

Refrigerants: If you had HVAC servicing with refrigerant top-ups, the service record should note the type and amount of refrigerant added. This goes into Scope 1.

Organize this data by source and by facility if you operate multiple locations. Most customers want facility-level breakdowns if your operations span different countries or regions.

Finding Emission Factors

Emission factors convert activity data into emissions. Reputable sources include:

For Electricity (Scope 2):

National government publications (DEFRA in UK, EPA eGRID in USA, etc.)
International Energy Agency (IEA) country-specific factors
Your electricity supplier may publish their specific factor

For Fuels (Scope 1):

DEFRA emission factors (UK government, but widely used internationally)
EPA emission factors (USA)
IPCC default factors (if country-specific data unavailable)

For Refrigerants (Scope 1):

IPCC Fourth or Fifth Assessment Report GWP values
EPA reference documents

Use emission factors from the same year or the most recent available. Many governments update factors annually to reflect changing grid composition and fuel standards.

Sample Calculation

Your small manufacturing facility consumed:

Electricity: 120,000 kWh
Natural gas: 15,000 kWh
Diesel (vehicles): 3,000 liters

Scope 2 Calculation (Electricity):

120,000 kWh × 0.233 kgCO2e/kWh (example grid factor) = 27,960 kgCO2e = 27.96 tCO2e

Scope 1 Calculation (Natural Gas):

15,000 kWh × 0.184 kgCO2e/kWh (natural gas factor) = 2,760 kgCO2e = 2.76 tCO2e

Scope 1 Calculation (Diesel):

3,000 liters × 2.687 kgCO2e/liter (diesel factor) = 8,061 kgCO2e = 8.06 tCO2e

Total Scope 1: 2.76 + 8.06 = 10.82 tCO2e Total Scope 2: 27.96 tCO2e Combined Scope 1 + 2: 38.78 tCO2e

You would report 38.78 tCO2e as your annual emissions. If your annual revenue was $5 million, your emission intensity would be 7.76 tCO2e per $1 million revenue.

Common Reporting Formats

Customers may request emissions through various channels:

Direct Questionnaires: Custom Excel or online forms asking for Scope 1, Scope 2, breakdown by source, and sometimes methodology.

CDP Supply Chain: Your customer invites you to complete a CDP questionnaire, which includes detailed GHG reporting sections.

EcoVadis: Asks for emissions data in the Environment section, along with evidence of how you calculated it.

Product-Level Data: Some customers want emissions per product unit rather than company total. This requires allocating facility emissions across products, which gets complex for multi-product suppliers.

The underlying data is the same across formats. Tools like ESG Passport help by storing your emissions data once and formatting it for different questionnaire requirements.

Documentation and Methodology Notes

Customers increasingly ask how you calculated emissions. Document:

Data sources (bills, fuel records, meter readings)
Emission factors used (source, year, geographic relevance)
Calculation methodology (GHG Protocol Scope 1 and 2 guidance)
Organizational boundaries (what facilities are included)
Reporting period

This transparency builds confidence in your data quality and speeds any verification or audit processes.

When Third-Party Verification Matters

For most small suppliers responding to initial customer requests, self-calculated emissions are acceptable. You don't need expensive third-party verification unless:

Your customer specifically requires it (rare for small spend suppliers)
You're making public climate claims or commitments
You want to participate in programs requiring verified data (SBTi, certain industry schemes)

Verification costs typically start at $5,000-15,000 depending on your complexity and the assurance level. It's a business decision based on customer requirements and strategic value.

What About Scope 3?

Some advanced customers ask suppliers to report their own Scope 3 emissions. For small suppliers, this can be challenging because it requires getting emissions data from your suppliers. Unless you have significant influence over your supply chain or specialized calculation tools, Scope 3 reporting may not be feasible.

If asked, be honest about your current capability. Many buyers understand that Scope 3 reporting cascades down supply chains over time. Providing high-quality Scope 1 + 2 data is your priority.

Building Capability Over Time

Your first emissions calculation will take the longest. Once you've established the methodology, identified data sources, and performed the calculations, annual updates become routine. Track the same data points monthly or quarterly to smooth the process.

As climate reporting requirements expand, suppliers who've built emissions tracking capability will respond faster and more confidently to customer requests. Starting with accurate Scope 1 + 2 reporting in 2026 positions you well for the likely expanded expectations in coming years.

The data you report isn't just compliance. It's a baseline for improvement, a demonstration of operational awareness, and increasingly, a requirement for preferred supplier status with customers committed to their own climate goals.