Some production steps put out more than the product: whey beside cheese, bran beside flour, trimmings beside a cut. What happens to the impact depends on which kind of output you say it is.
| Output type | What it is | What it does to the impact |
|---|---|---|
| Co-product | An output with value of its own | Takes a share of the impact up to the step it leaves, by mass. That share comes off your product. |
| By-product | A residue of little or no value | Takes no share (cut off). Your product keeps all of the impact. |
Waste and emissions are different again: they add their own impacts to the product.
Choosing the output type
On a production step, add the output and pick its Output type. The menu says what each choice does: Co-product, "Has value. Takes a share of the impact by mass." By-product, "Little or no value. Takes no impact." The row keeps a short note on it once chosen.
On food steps, a by-product that is more than a fifth of the step's output by mass is flagged, in case it should be a co-product: "This by-product is 35% of the step's output by mass. If it has value of its own, mark it as a co-product so it takes its share of the impact." On the final step the product itself counts towards that output. The check only works when every amount is a mass, so nothing is said for litres or units.
Material and packaging steps cannot put out a co-product.
How the share is worked out
A co-product's share is its mass against the step's product outputs: a step that makes 80 kg of product and 20 kg of co-product gives the co-product a fifth of the impact up to that step. Give both outputs as a mass (for example kg). If the co-product is in a different kind of unit from the main output, the share cannot be worked out, and Data issues lists the product under "Co-product measured in a different kind of unit from the main output".
Allocation by mass is the rule throughout: it is stated in every product report's Allocation and circularity note, in the PACT footprints you publish and on your Registry listings.
The Co- & by-products list
Products > Co- & by-products lists what the production steps of all your workspaces put out beside your products, one row per name. Choose Co-products, By-products or All above the list, and search by name. Each row has:
- Kind: Co-product or By-product.
- Comes from: the products it is made alongside. A co-product from another workspace says which.
- Impact per kg and Climate change per kg, as a range when it comes from more than one product. A by-product takes no share, so it has no figures.
A row appears once a product with a co-product or by-product output is calculated. The list is read only.
Click a row to open its own page, which also says when its figures were last calculated. It is read only too: its impact comes from the products it is made alongside, so to change it, edit the source product. There is one card per source product, with the facility and step it leaves, its amount, its share of the step by mass, its impact and climate change (and its GHG (GWP100) figure where there is one) for that amount and per kg, when it was calculated, its figures for each impact category, and the raw materials it is used as. A source product that is a draft is marked Draft. "Not per kg" means the amount is not a mass.
Using your own co-product as an ingredient
A co-product of one product can be an ingredient of another: whey from your cheese in your bakery range, say. In the product editor, search for it and pick it from the Co-products group. See Circular ingredients: co-products and residues.
- Its figures follow the co-product, by mass, each time the product it comes from is recalculated.
- A by-product used this way is cut off: its transport and your own processing of it count, and nothing from the step it leaves.
- It is entered in grams, and it has no supplier: it is made at your own site, so there is nothing to ask for and no supplier data request.
- A co-product whose amount is not a mass has no figure per kg, so it cannot be used.
On the co-product's page, Similar to names the catalogue ingredient it is most like, suggested from its name. Global Admins, Global Super Users and LCA Experts can Set or Change it on Footprinting and above. With several source products, pick which product's figures it uses: one product's figures are used as they are, never an average.
Where co-products show in your reports
- Product reports: a product that puts out co-products lists them in its full report's Product Details tab, with the step, amount, share and impact per kg of each. Their share is not in the product's figures. The Allocation and circularity note says what the product passes to each.
- Baseline, historical and forecast reports: each co-product is counted once. Each product shows its own share. A co-product's share, by mass at the step it leaves, is on its own line, less what the report's products use as an ingredient: they carry that part. A by-product takes no share. The report lists its co-products and by-products with what is counted on each line.
If a product's figures moved
A co-product made at a facility before the last one used to leave all of its impact with the product. It now takes its share, so a product with such a co-product shows a lower impact after its next calculation.
Volume reports used to leave each co-product's share inside the product that yields it. A report composed again shows each product's own share, with its co-products on their own lines, so a product's line can be lower. The report's total changes only where one of its products uses another's co-product, which used to be counted twice.