Littering involves throwing away waste in places not designated for it, harming the environment. This study introduces a strategy to encourage more use of Littergram, an app designed to fight littering. Littergram allows users to photograph litter and share these images publicly, alerting local councils to clean up the waste. The study aimed to increase user engagement with Littergram by implementing an intervention designed using the Behaviour Change Wheel (BCW), a comprehensive framework for developing behaviour change interventions. We developed and applied a digital campaign through emails, following BCW guidelines. The process began with identifying the behaviour we wanted to change. We conducted a survey to understand what influences this behaviour and selected techniques for changing behaviour based on these insights. The campaign involved sending targeted emails to Littergram users. There was an increase in the use of Littergram during the campaign, and growth returned to initial levels after the campaign ended. This outcome shows that the approach can effectively increase engagement temporarily. Future research should focus on challenges in maintaining long-term behaviour change.