Wastogram: Validation of a new tool to measure household food waste

Globally, over a billion tonnes of food is diverted to waste streams every year. To design and implement strategies to minimise food waste, it is critical to understand current food waste behaviours, including what, and how much, food is being wasted at the household level. The gold standard method to measure household waste involves the collection of food waste in a bin, which is then weighed and sorted. Where this type of analysis is not possible, or too expensive, self-report instruments are typically used – though this method is typically considered to have poor accuracy due to recall and social desirability biases. Several studies have used photographs to measure food waste, which has the potential to significantly reduce both participant and assessor burden. However, this approach has not been well-validated. Thus, the primary aim of the present study was to develop and test the psychometric properties of a photographic tool to document, measure and report food waste (the ‘Wastogram’). Given the novelty of the approach and the potential benefits associated with scaling this method, a secondary aim was to see if different training techniques (text instructions only versus text instructions plus a supplementary video) influenced adoption and/or compliance. Fifty-eight participants collected their household food waste over one week using all three measurement strategies, half of whom were provided with the instructional video. Findings revealed that the Wastogram was as accurate as the bin audit proxy measure (F (1,56) = 3291.76, p < .001, R2 = 0.98) and less onerous for the researcher to decipher food types and states. Further, the Wastogram was more accurate than the self-report measure, when compared to the bin audit proxy measure (F (1,56) = 71.06, p < .001, R2 = 0.56). For participants who were provided video instructions in addition to text instructions, the Wastogram accounted for 100% of the variation in bin caddy weight, compared with 96.4% for the group who received only text instructions. The findings of the present study suggest that the Wastogram methodology has the potential to accurately measure the impact of food waste reduction program at a lower cost than traditional bin audit methods. This could significantly improve our ability to accurately measure food waste at the household level and to better assess the impact of intervention programs subject to recall and social desirability bias.