When must I split a shared process's emissions by price instead of weight under the Partnership for Carbon Transparency (PACT) method?
PACT says allocation shall be avoided whenever possible. If not, divide the economic value of the highest-value co-product by the lowest. Above five, companies shall allocate by economic value. At five or below, companies should allocate by a physical link such as mass, if one exists; if none does, PACT says use economic value or another established factor.
Step 1: avoid splitting
Allocation means sharing one process's emissions among everything it makes, the way flatmates might split one electricity bill. Physical allocation shares by a measure such as weight. Economic allocation shares by money value. PACT says it shall be avoided whenever possible by splitting the process into parts so each part serves one product, only as far as needed to isolate your product. If that is not possible, PACT allows system expansion only when there is a dominant, identifiable displaced product and sector consensus. System expansion means crediting what your co-product replaces elsewhere.
Step 2: the price ratio
Put the economic value of the highest-value co-product on top and the lowest below, whether or not either is your product. PACT calls five an arbitrary number agreed with other footprint initiatives to show a large gap in value. Use stable market prices. If prices swing by more than 100% year on year, use the average of ideally the last five years, otherwise three. If prices are not available, justified costs may be used. Use one type of price across the whole footprint.
Step 3: pick the method
Whichever you use, disclose it and explain why it reflects each product's share.
- Ratio of five or lower: physical allocation, using the physical link that fits best, if a physical link exists. If none does, PACT says to use economic value or an established alternative factor. In doubt, prefer mass, though litres suit liquids and energy content suits fuels.
- Ratio above five: economic allocation, by value times quantity of each co-product.
- More than two co-products: the ratio is the highest-valued over the lowest-valued.
How it differs from the general page here
The general page follows the International Organization for Standardization (ISO) order: physical first, then economic. PACT adds the five test that tells you when to jump to economic.
One month at a mill, example numbers in rupees (Rs)
- Process emits 2,400 kilograms (kg) of carbon dioxide equivalent (CO2e). Main product 1,000 kg at Rs 60 per kg. Co-product 200 kg.
- Case 1, co-product at Rs 20 per kg: ratio 60 / 20 = 3, which is five or lower, so by mass. Main: 1,000 / 1,200 x 2,400 = 2,000 kg. Co-product: 400 kg.
- Case 2, co-product at Rs 5 per kg: ratio 60 / 5 = 12, above five, so by value. Main value 1,000 x 60 = Rs 60,000. Co-product value 200 x 5 = Rs 1,000.
- Main: 60,000 / 61,000 x 2,400 = 2,360.7 kg. Co-product: 1,000 / 61,000 x 2,400 = 39.3 kg. Total 2,400.0 kg
All numbers are examples. A rule written as value and quantity is how we read PACT's sentence on economic allocation. Using price per kilogram for the ratio is our reading; PACT's Figure 10 uses value per item.
What Senseible does here
Senseible reads fuel invoices and electricity bills into monthly records. Which co-product shares the emissions, and at what price, is your decision. Senseible builds figures in the PACT exchange format as a custom integration, on request.
Sources: PACT Methodology Version 3.0, World Business Council for Sustainable Development (WBCSD)
Last reviewed 2026-11-07. Steps are from PACT Methodology 3.0, section 3.3.1.4 and Figure 9. Using price per kilogram for the ratio is our reading; PACT's Figure 10 uses value per item. Check the version your buyer names, and any sector rule that overrides it.