The School Canteen Waste Audit
A Year 12 cross-disciplinary team is asked by the school council to reduce canteen landfill waste by 30% within one term. The team includes a student strong in Biology (compost science), one in Economics (cost-benefit), and one in Design and Technology (bin ergonomics). After a two-week baseline audit of 10 lunchtimes, they find 48 kg of waste per week: 22 kg food scraps, 15 kg soft plastics, 7 kg paper, 4 kg mixed recyclables. The canteen manager resists changing suppliers because of a three-year contract with penalties. The grounds staff say the compost bay is full and only accepts 10 kg per week. The team has a budget of A$600 and eight weeks. One member wants to start a social media campaign immediately; another insists they must first model costs.
1. Explain how the team should decide which single intervention to trial first, integrating at least two disciplines. Justify the choice with the audit numbers.
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The team should rank interventions by (a) the mass they can divert, (b) the constraint each discipline reveals, and (c) the time and money available.
Biology constraint: food scraps are the largest stream (22 kg/wk), but the compost bay accepts only 10 kg/wk. So composting alone can divert at most 10 kg/wk, about 21% of 48 kg - short of the 30% target (14.4 kg/wk).
Economics constraint: the supplier contract penalty means source-reduction via supplier change is off the table this term; that rules out the highest-leverage option and forces the team to work downstream.
Design and Technology: separating soft plastics (15 kg/wk) is feasible if labelled bins are placed at the point of waste generation. Diverting all 15 kg plus 10 kg compost = 25 kg/wk, about 52%, comfortably above target.
So the first trial should be a paired intervention: point-of-use soft-plastic separation plus capped composting. The social media campaign is premature because behaviour change without infrastructure produces contamination, and the team cannot yet measure it against the 30% target.
2. The social media advocate argues that awareness is the real problem. Evaluate this claim using the audit data and propose how the team could test it cheaply.
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The claim is plausible but untested. The audit shows mass by material, not by cause, so it cannot distinguish 'people don't know' from 'people can't easily do the right thing'. The presence of 4 kg of mixed recyclables in general waste is consistent with confusion, but also with inconvenient bin placement.
A cheap test within the A$600 budget: run a two-week signage-only condition in one canteen area (cost: printing, roughly A$40) and compare contamination rates in the recyclables stream against the baseline two-week period. If awareness is the binding constraint, contamination should fall measurably. If it does not, the infrastructure hypothesis is supported.
This is a controlled comparison using a single changed variable, which is the cross-disciplinary move: the Biology student defines contamination (visual inspection of the recyclables bag), the Economics student frames it as a low-cost experiment with a decision rule agreed in advance (e.g., 'if contamination falls by less than 20%, we move to bins'). The team should write that rule before running the test to avoid post-hoc rationalisation.