When a major retailer declares it has reached net zero, what that usually means is it has addressed its Scope 1 and 2 emissions — the fuel it burns directly and the electricity it buys. What it often excludes is Scope 3: the emissions embedded in its supply chain, its logistics providers, the business travel of its employees, and the eventual disposal of its products. In most industries, Scope 3 represents 70–90% of the total carbon footprint.

The Three Scopes of Carbon Emissions

The GHG Protocol Corporate Standard — the global framework used by the vast majority of large companies — divides emissions into three scopes:

• Scope 1: Direct emissions from sources your company owns or controls — company vehicles, on-site boilers, fugitive refrigerant leaks.
• Scope 2: Indirect emissions from the electricity, heat, or steam you purchase. These happen at the power plant, not at your facility.
• Scope 3: All other indirect emissions across your value chain — both upstream (suppliers) and downstream (customers, product end-of-life).

Scope 3 contains 15 distinct categories defined by the GHG Protocol Scope 3 Standard, ranging from purchased goods and services to investments.

Why Scope 3 Is So Large

Consider a smartphone manufacturer. Its Scope 1 emissions — the gas it uses to heat its offices — might be a few hundred tonnes of CO2 per year. But the mining of lithium, cobalt, and rare earth minerals; the energy-intensive manufacturing of components in Southeast Asia; the freight shipping of finished goods; and the eventual landfilling or recycling of devices could easily total millions of tonnes. The same logic applies to food companies, apparel brands, and financial services firms.

A McKinsey analysis found that supply chains account for more than 80% of greenhouse gas emissions for most industries. Ignoring Scope 3 is not a conservative approach — it is a fundamentally incomplete one.

The 15 Categories of Scope 3 Emissions

The GHG Protocol organizes Scope 3 into upstream and downstream categories:

Upstream (Categories 1–8)

• Category 1: Purchased goods and services
• Category 2: Capital goods
• Category 3: Fuel- and energy-related activities (not in Scope 1 or 2)
• Category 4: Upstream transportation and distribution
• Category 5: Waste generated in operations
• Category 6: Business travel
• Category 7: Employee commuting
• Category 8: Upstream leased assets

Downstream (Categories 9–15)

• Category 9: Downstream transportation and distribution
• Category 10: Processing of sold products
• Category 11: Use of sold products
• Category 12: End-of-life treatment of sold products
• Category 13: Downstream leased assets
• Category 14: Franchises
• Category 15: Investments

Why Scope 3 Reporting Is Now Mandatory for Many Companies

Regulatory pressure is accelerating rapidly. The EU's CSRD requires large companies — and eventually their supply chain partners — to report Scope 3 emissions starting in 2025. California's SB 253 (Climate Corporate Data Accountability Act) requires companies with revenues over $1 billion operating in California to disclose Scope 3 from 2027. The SEC's climate disclosure rules also include Scope 3 for larger registrants.

Even for companies not yet legally required to report, major customers increasingly require supply chain emissions data as part of their own Scope 3 accounting. If your clients are listed companies in regulated jurisdictions, they will eventually ask you for this data.

How to Start Measuring Scope 3 Emissions

The data collection challenge is real, but it is manageable if you take a structured approach:

1. Identify which Scope 3 categories are material for your business — focus on the two or three largest sources first.
2. Collect activity data: supplier invoices, freight weight and distance, employee travel records, waste disposal records.
3. Apply emission factors from recognized databases (DEFRA, IEA, USEPA) to convert activity data into CO2e.
4. Use spend-based estimation for categories where primary data is not available — multiply expenditure by an industry-average emission intensity factor.
5. Set a baseline year and track progress annually.

Tools That Can Help

A carbon calculator that covers the full scope of GHG Protocol categories significantly reduces the data collection burden. Climate Tally's business calculator supports Scope 1, 2, and 3 emissions — including freight transport, business travel, hotel stays, employee commuting, refrigerants, and waste disposal — using verified emission factors from DEFRA, IEA, UNFCCC, and other recognized sources.

You can calculate your emissions for free, generate a detailed breakdown by category, and identify which Scope 3 sources are driving your footprint.