Comparing wasted apples and oranges: An assessment of methods to measure household food waste.

Food waste has become a global concern in recent years, especially the household food waste that is generated in the developed world. Multiple methods to measure household food waste have been proposed, but little is known about their validity. Five methods are selected and investigated empirically: survey questions about general food waste over a non-specified period of time, diaries, photo coding, kitchen caddies, and pre-announced survey questions regarding a specific time period. In an experiment, respondents were asked to assess their food waste using some or all of these methods depending on condition. Overall, the general survey questions appear to be less valid, as these lead to large underestimation of the level of food waste, low variance in reported food waste across households compared to the other methods, and low correlations with other measures. The other four methods are relatively highly correlated. A survey about food waste in the past week appears to be a useful method for large-scale measurements to differentiate households according to the amount of food waste each produces, although it should be noted that this method underestimates the amount of food waste. Kitchen caddies and photo coding seem to be valid methods and, for small samples, provide alternatives to food diaries, which have been more commonly used.