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. 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".
The Co-products list
Products > Co-products lists what your production steps put out beside your products, one row per co-product name:
- Comes from: the products it is made alongside, each linking to its report.
- Impact per kg and Climate change per kg, as a range when it comes from more than one product.
- Calculated: when its figures were last worked out.
Search by name to find one. A co-product appears once a product with a co-product output is calculated. The list is read only.
Open a co-product for its own page. 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 for that amount and per kg, when it was calculated, and its figures for each impact category. A source product that is a draft is marked Draft. "Not per kg" means the amount is not a mass.
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.
- Baseline and historical reports: co-products have no volumes of their own yet, so each product carries the full impact of the co-products it yields, and the report says "Co-product impacts are included in this report."
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.