Split a kitchen experiment into three named jobs — noticing, recording and deciding — give each to a person, and fix the date it stops before it starts. One person doing all three is not a shared experiment; it is supervision. Start with the largest reason rather than the most annoying one: cooking, preparing or serving too much accounted for 1,094,000 tonnes, 25% of the 4.4 million tonnes of edible food UK households binned in 2022, worth £4.95 billion, in WRAP's UK food waste key facts. The condition that changes the design is who controls the shopping: if only one person buys the food, the recording job belongs to the other one.

Three jobs, two people, one stop date

Write the action small enough to check in a sentence: for the next four weeks, we weigh the potatoes that go in the bin. Not "we will waste less". A broad aim hides the work and leaves nobody able to say which part helped.

Noticing is seeing the item before it is thrown out. Recording is writing the entry within the day. Deciding is the conversation at the end, which belongs to both. Rotate noticing and recording at the halfway point so neither person spends four weeks watching the other.

Agree the stop condition in the same sitting. A workable one names a symptom and a response: if writing entries starts interrupting work, we drop to one entry a week; if the notes start feeling like an inspection, we stop recording and talk once. A stop condition is what makes "this does not fit us" a result rather than a failure.

Agree what is written and what is not. An item and an approximate amount is enough. Names beside entries, photographs of receipts and access to another person's spending are not part of the design, and a household that lives separately shares only what it chooses to.

Fairness here has a published definition

The European Environment Agency's briefing 18/2023, published on 3 October 2023, sets out why participation has to fit its purpose and leave room for people to express different concerns; it traces the right to take part in environmental decisions to the Aarhus Convention of 1998. Applied at a kitchen table, that means each person can refuse a role, propose another, and disagree with the change without leaving the experiment.

There is a reason the unit is a household action rather than a household verdict. The EU's binding food-waste targets under the 2025 amendment to the Waste Framework Directive, Directive (EU) 2025/1892, are a 10% cut in processing and manufacturing and a 30% per capita cut jointly at retail and consumption by 2030, measured against the 2021 to 2023 average (food waste reduction targets). Retail and consumption sit in the same target as restaurants; no kitchen carries that alone.

An example four-week agreement

One experiment, worked through with its arithmetic. Two people pick potato, the most wasted single item in UK homes in the 2022 data, with around 480,000 tonnes thrown away that year — 480,000 ÷ 365 = about 1,315 tonnes a day, or 1,315,000 kg ÷ 0.16 kg = roughly 8.2 million potatoes a day at an average 160 grams each (key facts).

Scaled to two people: potato is 480,000 ÷ 4,400,000 = 10.9% of UK household edible food waste, and 65 kilograms per person a year × 0.109 = 7.1 kilograms, so 7.1 kg ÷ 52 = 136 grams a week each. Over four weeks, 0.136 kg × 2 people × 4 weeks = 1.09 kilograms, which at £260 ÷ 65 kg = £4.00 a kilogram is 1.09 × £4.00 = £4.36, or about seven potatoes at 160 grams.

Four pounds over four weeks is the honest size of the prize, and it is why the effort column matters as much as the weight column. At the end, ask two separate questions: what happened to the potatoes, and what did the recording cost each person in minutes. Do not average one person's substantial extra work away because the other found it easy.

Keep the change, shrink it or drop it, and write the reason in plain words: fewer duplicate bags but too many messages; no pattern; useful check, manageable effort. A clearer handover or a job somebody can finally decline is a real outcome, and it is the same fairness test that applies before joining anything in what would make an environmental activity worth joining. If the counting itself is the problem, run the shorter version in a week of less food waste, together instead.

Sources