• Opinion
  • December 4, 2019
  • 11 minutes
  • 0

How to collect waste like a behavioural scientist

Opinion: If you are reading this, chances are you produce 1 kg of waste per day

This article was written by Jorge Luis Castaneda, an economist at the Mind, Behavior and Development unit (eMBeD) at the World Bank. For more like this, see our government innovation newsfeed. 

By 2016, the global population generated 2.01 billion tonnes of solid waste annually worldwide. This is roughly equal to 270 kilograms per person, with the largest share coming from developed nations. If you are reading this article, you are most likely producing around 1 kg of waste every single day.

As governments consider policies and programs meant to improve environmental outcomes and to reduce and waste generation, the individual behaviour of citizens and consumers is essential to the effective and sustainable operation of waste management systems. The Argentinean Municipality of Trelew, with 225,000 inhabitants in its metropolitan area, is an excellent example of the potential for governments and its citizens to move towards a circular economy, especially in the developing world.

The city, located 1.200 kilometres south of Buenos Aires on the shores of the South Atlantic Ocean, has invested in most of the necessary infrastructure to ensure sustainable waste management. Firstly through a recycling plant, constructed in 2013 and funded by the World Bank, to separate and process recyclable material. Additionally, it has implemented a differentiated kerbside collection system, with recyclables gathered and sent to the plant once a week, and the rest of the waste carried daily to the local landfill.

So, the city has put all the necessary infrastructure for effective waste management in place. However, only 3% of the city’s waste is recovered through recycling, with the remainder rapidly piling up in the local landfill. 

Furthermore, at the waste separation plant, workers sort through mixed and often hazardous garbage to extract and recover recyclables, resulting in significant time and resource costs and deterioration of health and general work conditions of employees. In principle, if Trelewenses separated the recyclables from residual waste and took them out on the designated day, then classification at the plant would be quick and efficient, and recovery high. 

But changing people’s habits is difficult, and so the city turned to behavioural science for help.

Throwing behavioural science at waste management

Working with the Municipality of Trelew, the World Bank’s Mind, Behavior, and Development Unit (eMBeD), together with the German Development Institute (DIE), sought to use behavioral science to improve waste separation rates by incentivising two key consumer behaviours: separating waste at the source into the two categories — recyclable and residual — and disposing recyclables only on the appropriate day indicated by the Municipality.

The team then sent letters and magnetic calendars with different messages to approximately 4.800 recipients in Trelew. 90% of these calendars and letters were sent to households, and the rest were sent to small businesses. The goal was to increase the salience of the correct collection day for recyclables (“Recyclables: Only on Thursdays. Thursdays: Only recyclables”), as well as prosocial messages (emphasising the benefits to society and others) about why individuals should make an effort to separate waste (“If you separate, you help us!”).

the simple, salient, and motivating messages doubled waste separation from 17% among citizens in the street blocks that didn’t receive the letters and calendars to 31% in the blocks that did

Therefore, the team designed and tested two sets of materials: a behaviourally-informed set, providing reader-friendly, clear, and salient information on the collection process, and a second motivational set with images and quotes of plant workers depicting their essential role and harsh labour conditions.

To test whether or not it had worked, the team collected the waste of 899 randomly selected disposal points two weeks after distributing the letters and calendars. They collected a total of 3.5 tons of garbage and measured each bag’s weight, volume, and waste classification. Additionally, the team conducted short surveys with 2.700 households focusing on waste separation practices over the weeks following the intervention.

Low cost, high impact

The results were promising for future communication and policy design. Ultimately, the letters and calendars doubled waste separation from 17% among citizens in the street blocks that didn’t receive the materials to 31% in the blocks that did, two weeks after the distribution of the materials. Both sets, the behaviourally informed and the motivational, worked similarly well, and between three and six weeks later, over 80% of surveyed participants stated that they had kept the material.

The intervention was also cost-effective, at an average of only $0.55 USD per participant. When weighed against the economic benefits of reduced pressure on the landfill, increased revenue from the sale of recyclables, ecological relief from reduced pollution, as well as the reduced risk of hazardous working conditions for plant workers, the cost seems quite reasonable.

Moreover, the results have the potential for long-term sustainability. Therefore, the team is currently collecting data to determine if the effects are persistent and whether different messages and information materials might incentivise different behaviours in the long term.

Replicate a success

For us at the eMBeD team at the World Bank, two elements in this and other interventions stand out as a way to ensure success in projects that rely on behavioural science.

First, you should do a careful analysis of the context, target behaviours, and exhaustive diagnostics. Our collaborative diagnosis and validation work led by DIE included reviews of the relevant literature on waste management from behavioural sciences, collecting and analysing a household survey, and consulting citizens, local authorities, and experts.

Only then we were able to select precise target behaviours of separating and disposing of recyclables, identify the lack of awareness as a constraint to these behaviours, and design useful communication materials that delivered simplified information on the recycling process and the fundamental role of households in it.

We are returning to the drawing board to create interventions that go beyond waste separation and that tackle some of the root causes of unsustainability, such as waste generation and preservation and control of wildlife


Second, and even more relevant, the close collaboration with the local government and DIE provided a fruitful synergy of knowledge and practice. In this case, co-ownership of the intervention and its impacts was also crucial, with local authorities taking an interest in participating and providing their unique contextual knowledge at every step of the project, continuously remaining receptive to capacity development activities, and co-leading multiple implementation tasks. To name a few, the preparation and distribution of the materials, the planning of the field activities, and the training of the collection teams.

Furthermore, the close collaboration between lead experts and researchers from DIE and the World Bank allowed for dynamic knowledge exchange, creative thinking process, and cross-pollination between institutions. To achieve this integration, the teams kept a constant dialogue between all team members from the three institutions.

As field experiments require careful planning and timely problem solving, the group met weekly and maintained an open conversation and consultation with experts mostly through mobile messaging, overcoming the challenge of coordinating over multiple time zones. Additionally, the local authority designated a team of highly qualified and motivated officials to this project, which, as mentioned, was vital for our success.

One small step towards sustainability

We are looking forward to seeing the data on sustained impact, as it is currently being analysed at the time of writing.

We are likewise excited to work with governments to increase the scale of behaviourally informed initiatives to promote innovative solutions for sustainability. Concretely, we are returning to the sketch board to create interventions that go beyond waste separation and that tackle some of the root causes of unsustainable behaviours, such as waste generation and preservation of wildlife.

And, in parallel, we are starting the conversation with other Argentinean municipalities willing to explore and experiment on these additional areas. As sustainable development depends on governments and their citizens, our goal will be to continue testing behaviourally-informed policy tools with the potential of being replicated in different geographies and applied to a broader set of policy issues. — Jorge Luis Castaneda

If you want to learn more about how to embed behavioural science in public policy, follow this link to watch Jorge Luis Castaneda present his insights in a live webinar for Apolitical members.

Picture credit: Unsplash)


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