By slightly changing the order screen, carbon emissions can be reduced — from CO₂ 2,280g to 1,530g. How the "default settings" of a delivery app changed the weight of a meal.

The University of Bonn in Germany conducted a study to examine how much CO₂ emissions could be reduced by changing the UI of a food delivery app. In an experimental app, 1,011 participants created burger sets, and a "nudge" approach was used by setting climate-friendly menu options as the "default choice" and placing them at the top of the list with a green leaf icon. This approach reduced emissions to an average of 1,530g, a reduction of about 30% from the control group's 2,280g. On the other hand, "boost" methods such as providing hints or displaying real-time CO₂ emissions had a smaller effect. However, one week later, all groups reverted to their original choices, indicating no lasting effect. It's important to note that the study was conducted with a virtual app and not actual purchases, but it suggests that designing with "eco by default" is effective in the short term. Previous online experiments have also observed an average reduction effect of 12% by rearranging menu items, indicating that repetition and combined interventions might be key.