Southeast Asia is no stranger to the plastic crisis. Despite growing awareness and countless"reduce, reuse, recycle" campaigns, single-use plastic consumption remains stubbornly high.
The big question is, why?
Plastic pollution is not just a waste management problem -- it is also a behavioural issue. At its core, plastic use is a human-driven problem. Habits, convenience, and social norms often override good intentions, even when its consumers understand the harm plastic poses to the environment. Without addressing these behavioural drivers, policies and technologies will always fall short.
Achieving net-zero plastic waste requires a change in how people think about and interact with plastic -- and that starts with behavioural science, which offers powerful tools to design plastic reduction strategies by addressing these psychological and social drivers. While bans and taxes can help with compliance, they often fail to foster lasting change.
Effective interventions must include financial incentives, visual cues, and social influence to make sustainable behaviour feel easier, more attractive, and more rewarding. This approach is central to a pioneering initiative led by the Regional Knowledge Centre for Marine Plastic Debris at the Economic Research Institute for Asean and East Asia, in collaboration with the Institute for Global Environmental Strategies (IGES) and Rare's Center for Behavior and the Environment.
The programme piloted behavioural interventions across four Asean countries, with measurable results.
In Indonesia, a project at the University of Indonesia which is implemented by the Center for Southeast Asian Studies aims to reduce plastic straw and cup usage by altering the default option in canteens and cafes.
At the canteen, plastic straws were removed from customers' view. They are required to pay Rp2,000 or about 4 baht for request one. As a result, straw usage plummeted by nearly 99% -- from 6,825 to just 74 per month.
Meanwhile, a coffee chain on campus offered a 10% discount for those who bring their own reusable tumblers, supported by emotionally appealing messages on posters and staff uniforms. Although cup use dropped by 49%, the disparity in impact between the traditional canteen and the coffee chain highlighted a crucial behavioural insight: asking people to opt in requires higher effort and motivation. This demonstrates how even well-intentioned incentives can fall short when they do not align with real-world habits and cognitive shortcuts.
In the Philippines, the University of the Philippines Diliman redesigned vendor practices to promote plastic-free vending. Vendors were provided compostable alternatives, refill stations replaced bottled drinks, and discounts were offered for bringing reusable containers.
The result was a 43% drop in single-use plastic use amongst participating vendors. However, only 6.5% of students consistently brought their own containers, suggesting that the incentive (a 5-, or three-baht, discount) was too small to overcome ingrained habits. The findings also underscore the importance of high-quality, functional alternatives -- some students reported issues with flimsy compostables which don't work with soups and cold drinks.
This became even clearer in Bangkok, Thailand, where two markets -- the Chulalongkorn University Market and Samyan Market -- offered a natural behavioural comparison. At the Chulalongkorn University Market, which is part of the long-running Chula Zero Waste initiative, material incentives such as a two-baht bag fee and free tote bags were combined with emotional appeals and social influence cues -- including posters, mascots, and student-made videos. These interventions, which embedded the culture of sustainability into everyday student life, resulted in a 94% drop in plastic bag use.
In contrast, Samyan Market saw only a 6.7% reduction despite introducing a similar fee, as it lacked consistent messaging and institutional backing. The intervention failed to create cumulative behavioural cues that make sustainable behaviour visible, easy, and socially expected. This comparison highlights that behavioural nudges -- whether financial, emotional, or social -- must work in concert with social systems and institutional infrastructure and be deeply embedded in the environments and communities they seek to change.
This principle holds true beyond markets and campuses. In Vietnam, a pilot project led by the Southern Institute of Ecology demonstrated that behavioural change, especially amongst the youth, is not an instant shift but a gradual, evolving process.
In Ho Chi Minh City, students and teachers of Thanh Loc and Hiep Binh high schools creatively tackled single-use plastic reliance and poor waste practices. The project encouraged students to be a model for sustainable practices for others, with regular activities such as waste audits, creative contests, and visits to recycling facilities.
While plastic waste dropped by 4.8% and 12.4%, the more important outcome was the surge in student participation and leadership. Although knowledge about plastic pollution remained relatively stable, the pilot fostered emotional engagement, public commitments and a sense of ownership, planting seeds for long-term behaviour change through heightened peer accountability.
The path to net-zero plastic waste is not just about traditional policy instruments and technological innovations -- it is also about reshaping everyday behaviour. Behavioural change must be embedded into every systemic transformation by integrating behavioural insights into policymaking, education, urban planning, product design, and waste management systems. Achieving this, however, requires more than isolated efforts; it calls for a network of committed actors working together to bridge knowledge gaps, scale effective solutions, and align incentives.
By connecting these insights, we can design environments where plastic-free choices become easier, more visible, and socially supported. If Southeast Asia and the world truly want to break free from plastic dependence, we must make behavioural insights as central to policy design as regulations and technology. Only by addressing the human side of the problem can we build a sustainable, net-zero plastic future for generations to come.
Celine Kusnadi is research associate at the Regional Centre for Marine Plastic Debris at the Economic Research Institute for Asean and East Asia.