In summary, this report provides evidence that nudges can be effectful in steering people’s choices towards reusable cups instead of single-use cups. It should, however, be noted that the effectiveness of the nudges is not guaranteed. It’s highly context dependent and a thorough understanding of the operational context is crucial for maximizing the potential impact of the nudge.
The field experiments conducted in various settings revealed that a normal implementation with a dynamic approach yielded significantly higher increases in sustainable behaviour, with prompts showing the most consistent effect. The lottery mechanism and the descriptive social performance feedback loop were also effective, particularly in closed settings. These findings suggest that the same nudge can have varying impacts in open versus closed settings, highlighting the importance of understanding the context in designing interventions. Additionally, the study indicates that simple sign-based interventions, while cheap to implement, are not particularly effective in reducing single-cup waste on their own. However, combining signs with prompts, social performance feedback, or lottery mechanisms can enhance their impact on promoting sustainable alternatives. It is also important to note that nudging should have a greater potential to influence behaviour if implemented already in the design phase of circular solution system set-ups, rather than as an addition to already existing solutions. Nudges are no silver bullet solution and should rather be seen as a complement to other efforts in increasing the use of reusable cups. While stronger policies such as regulations banning the use of single-use cups may be more impactful, these would also create a new behavioural challenge with the increased need to make sure that the reusable cups are actually reused and not disposed, which would only exacerbate the environmental issues.
Our recommendations for businesses that want to increase the uptake of reusable cups include using prompts for customers and enhancing saliency to create awareness and facilitate successful prompts. We do not endorse mandating prompts, but rather encouraging a voluntary employment of both prompts and saliency. Further investigations would be warranted for successful implementation of nudges at larger scale. Investigations of monetary incentives for both businesses and customers, as well as awareness campaigns and joint return systems in collaboration with coffee shops could also be avenues for further testing.