In what order does the Greenhouse Gas Protocol want me to try the four Scope 3 Category 1 methods for a purchased good?

The Greenhouse Gas (GHG) Protocol's decision tree starts with screening: does the purchase matter to your Scope 3 or to supplier engagement? If yes, it asks for physical quantities, then product-level supplier data, then allocated Scope 1 and 2. If no, it picks average-data or spend-based.

The tree, step by step

1. Screening: does this good or service contribute significantly to your Scope 3 emissions, or is supplier engagement otherwise relevant to your business goals?
2. If yes, do you have data on the physical quantity bought? If not, use the spend-based method.
3. If you have quantities, can the tier 1 supplier give product-level cradle-to-gate data of sufficient quality? If yes, use the supplier-specific method.
4. If not, can the supplier give allocated Scope 1 and 2 data of sufficient quality for the good? If yes, use the hybrid method. If not, use the average-data method.
5. If step 1 was a no, the tree only asks about quantities: with them, average-data; without them, spend-based.

Rules around the tree

• The guide says companies need not always use the most specific method as a first preference.
• You may use different methods for different goods and services within Category 1, for example more specific methods for the categories that contribute most.
• The guide says collecting data from suppliers adds considerable time and cost, so companies should screen first to prioritise.
• Sufficient quality means the inventory most appropriately reflects your emissions, supports your business goals and serves the decisions of the people who use it.

What decides each fork

Reading the tree as a whole (our reading): supplier data decides between the top three methods, and quantity data decides between average-data and spend-based. A buyer with tax invoices that show quantity and unit has the quantity data for most goods already, so spend-based is the fallback for services and items billed only in rupees.

Four purchases of a fabricator, sent down the tree

• Steel plate: large share of purchases, tonnes on the invoice, mill gives no product figure and no allocated Scope 1 and 2: average-data
• Coated packaging film: large share, the supplier sends allocated Scope 1 and 2 for the film sold to you: hybrid
• Cutting oil: small share, litres on the invoice: average-data
• Courier fees: small share, only the rupee amount is known: spend-based

This is our reading of the guide's tree applied to example purchases. It carries no factors. A supplier that later sends a product-level figure of sufficient quality moves the steel or film up to supplier-specific.

What Senseible does here

It does not choose a Category 1 method for you. Senseible keeps purchase invoices on the Scope 3 trail so the quantity each branch needs is on file.

• Is a supplier figure always better than an average?
• Production and non-production purchases
• Filling gaps in Scope 3 data
• Scope 3 supplier evidence

Sources: Greenhouse Gas Protocol Technical Guidance for Calculating Scope 3 Emissions, Category 1 (Figure 1.2 and the method summary)

Last reviewed 2026-11-05. The tree is from Figure 1.2 as drawn in the guide. The purchases in the example are examples chosen to show the path.