How much of the supplier estimate is documented?
Alder Climate Team checks a fictional materials buyer’s estimate for 1,000 purchased tonnes.
The question
The team counts emissions through delivery to the warehouse. The factors give tonnes of carbon dioxide equivalent (tCO₂e) per material tonne. Measure data coverage by purchased mass.
| Documented supplier factors | Sector proxy | |
|---|---|---|
| Purchased material (tonnes) | 600 | 400 |
| Factor (tCO₂e per material tonne) | 0.8 | 1.5 |
Both opening factors cover delivery to the warehouse.
“Calculate the estimate and update the coverage when the supplier sends more detail.”
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A strong answer, step by step
Open each step in turn. This is one strong answer, not the only one.
Step 1: What is the opening estimate?
What would you do here? Open the move you’d make.
Use an average of the two factors across all tonnes
Tempting, but it misses something. The two factors cover different amounts of material.
Weight each factor by the tonnes it covers
The strong move. That gives the total and preserves the supplier-specific share.
Report only the 480 tCO₂e from documented factors
Tempting, but it misses something. The sector proxy estimates the emissions associated with the other 400 tonnes.
See how a strong candidate says it
“The supplier-specific part is 480 tCO₂e. The proxy part is 600 tCO₂e. The total is 1,080 tCO₂e, with documented factors for 60% of purchased mass.”
Why it works: Multiply each factor by the tonnes it covers. Coverage uses tonnes purchased as its denominator.
Step 2: How would you label the AI draft?
An AI draft labels all the tonnes as supplier-specific because every row has a factor.
What would you do here? Open the move you’d make.
Keep the full estimate and name the proxy share
The strong move. The reader can distinguish missing supplier data from missing quantities.
Leave the label as fully supplier-specific
Tempting, but it misses something. The sector factor does not describe the supplier’s own product.
Treat undocumented supplier factors as zero emissions
Tempting, but it misses something. An unknown supplier-specific value does not make the associated emissions zero.
See how a strong candidate says it
“I would report an estimate for the full 1,000 tonnes and label 40% of purchased mass as proxy-based. Only 60% has documented supplier-specific factors.”
Why it works: A number on each row gives full estimate coverage. Its source determines whether it is supplier-specific.
Step 3: What changes when the data arrive?
A supplier gives a factor of 1.2 for 250 tonnes in the proxy group and says it covers the agreed boundary. The purchase quantities are unchanged.
What would you do here? Open the move you’d make.
Describe the 75 tCO₂e difference as an achieved cut
Tempting, but it misses something. The new factor changed the estimate. There is no evidence that operations changed.
Apply 1.2 to all 400 tonnes in the proxy group
Tempting, but it misses something. The new factor covers only 250 tonnes.
Replace only the covered factor and label coverage provisional
The strong move. The remaining 150 tonnes keep the proxy while the team checks the new boundary.
See how a strong candidate says it
“The updated estimate is 1,005 tCO₂e. The supplier data provisionally cover 850 tonnes, or 85%, pending a boundary check. The 75 tCO₂e change comes from a new factor for the same material.”
Why it works: The estimate changed while the amount purchased and the activity in the packet stayed the same.
Step 4: Does the factor cover delivery?
The boundary review shows the new factor stops at the factory gate. Use a separate delivery proxy of 0.2 tCO₂e per material tonne for those 250 tonnes.
What would you do here? Open the move you’d make.
Keep the 1,005 total and 85% complete coverage
Tempting, but it misses something. The new supplier factor leaves out a part of the agreed boundary.
Add the delivery proxy and report both coverage figures
The strong move. This restores the delivery scope and shows which part still needs supplier data.
Add the delivery factor to every purchased tonne
Tempting, but it misses something. The two opening factors already included delivery for all other tonnes.
See how a strong candidate says it
“Delivery adds 50 tCO₂e, bringing the estimate to 1,055. There are some supplier-specific data for 85% of the mass. Complete supplier-specific data at the delivery boundary still cover 60%.”
Why it works: The new group has a supplier factor for part of the boundary and a proxy for delivery.
The answer, in short
- Decision
- Separate the emissions estimate from the share with complete supplier data.
- Because
- A factor can cover some processes and leave others to a proxy.
- What would change it
- Supplier-specific delivery data would change both the estimate and complete coverage.
Common traps
- Use purchased mass as the coverage denominator.
- Record boundary changes separately from activity changes.
Check your answer
- I weighted the factors.
- I labeled proxies.
- I explained the estimate revision.
- I reported both coverage figures.
Last reviewed Nov 11, 2026