Abstract

Food waste is a global issue with serious economic, social, and environmental consequences.

In Auckland, New Zealand, around 45% of household refuse that goes to landfill is composed of food waste. The aims of this study were to evaluate a range of behavioural science interventions to increase usage of Auckland Council’s kerbside food scraps collection service in pilot areas, prior to a city-wide roll out in 2023. Two separate randomised field experiments were run, in the pilot areas of Papakura and North Shore, measuring food scrap bin set out rates prior to interventions being delivered, immediately post-intervention, and seven weeks post-intervention. In the Papakura trial we randomly assigned 2,459 households, clustered into streets, to one of five treatment conditions – a proscriptive sticker prompt, attached to households’ refuse bins; a postcard with appeals to social norms; free liners for kitchen food scraps caddies; household canvassing; and a no-treatment control. In the North Shore trial 1,513 households, clustered into streets, were randomly assigned to one of three treatment conditions – free caddy liners plus a postcard with appeals to social norms; free caddy liners plus household canvassing; and free caddy liners alone. In the Papakura trial, we found evidence that the sticker prompt and postcard treatments increased set out compared to a control condition. They also showed a positive effect of the sticker prompt treatment on participation (set out at least once over 3 weeks). In the North Shore trial, results showed an overall pre versus post increase of the interventions on set out and participation, and a positive effect of the postcard treatment on set out, when compared to free caddy liners alone. These findings indicate sticker prompts and social norms messaging are two promising low-cost and scalable solutions to increase use of food scraps collection services and divert food from landfills, nationwide and abroad.

A thesis submitted in fulfilment of the requirements for the degree of Master of Science in Psychology, the University of Auckland, 2023.

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University of Auckland, Auckland Council Waste Solutions Team