Monitoring environmental burden reduction from household waste prevention

•Amount of prevented household waste was quantified using three methods based on a different baseline.•Amount of prevented waste was quantified as absolute change from the potential waste generation.•Greenhouse gas emission reduction by waste prevention and recycling was compared.•Setting a baseline is essential for evaluating waste prevention. In this study, the amount of prevented household waste in Kyoto city was quantified using three methods. Subsequently, the greenhouse gas (GHG) emission reduction by waste prevention was calculated in order to monitor the impact of waste prevention. The methods of quantification were “relative change from baseline year (a),” “absolute change from potential waste generation (b),” and “absolute amount of activities (c).” Method (a) was popular for measuring waste prevention, but method (b) was the original approach to determine the absolute amount of waste prevention by estimating the potential waste generation. Method (c) also provided the absolute value utilizing the information of activities. Methods (b) and (c) enable the evaluation of the waste prevention activities with a similar baseline for recycling. Methods (b) and (c) gave significantly higher GHG reductions than method (a) because of the difference in baseline between them. Therefore, setting a baseline is very important for evaluating waste prevention. In practice, when focusing on the monitoring of a specific policy or campaign, method (a) is an appropriate option. On the other hand, when comparing the total impact of waste prevention to that of recycling, methods (b) and (c) should be applied.