Labelling food with its carbon footprint encourages people to eat more sustainably, according to a field experiment conducted by researchers from Germany and Finland. The decisive factor is how the information is presented, with the effect greatest if carbon information was visualised in traffic light colours, or presented in environmental costs.

The ten-day field experiment was carried out at one of Munich Student Union’s largest canteens. During the test period, more than 8,000 visitors were not only shown the usual information on the menu displays, such as the prices of the respective dishes or their main ingredients, but also how high the carbon footprint was.

The display of the carbon dioxide, CO₂, information was changed once a day during the experiment to test which display methods had the most significant influence on consumer behaviour. A code additionally supplemented the information in traffic light colours (green, yellow, red), which ultimately had the most significant effect when visitors were told how much environmental damage their lunch had, a figure expressed in Euros. In this way, up to almost ten per cent less CO₂ was caused by the meals than without the information about CO₂ emissions.

The research was done by the ‘Collaborative Research Centre TRR 266 Accounting for Transparency’ of the universities LMU (Munich), HU (Berlin) and Aalto University (Finland).