Street bins: an untapped potential

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Public waste containers are street furniture placed in public spaces such as parks, streets, squares, etc. These trash bins aim to improve the social environment by encouraging people not to leave litter behind. However, the right choice of the type, number, and location of public trash bins remains an important decision to be made by road authorities.

To have a cleaner city, do we need to clean more? To ask the question is almost to answer it.

A properly disposed waste does not need to be picked up by the city's cleaning services. When I dispose of my waste in the designated areas properly, I preserve the quality of my urban environment and I do something beneficial for the environment. Without realising it, I even relieve my wallet, because if I litter this waste on the road, I would pay for its collection through my taxes. And on top of that, I improve my self-esteem! In an experimental study on littering behaviour, Dr Rebekka Gerlach, affiliated with the Humboldt University ZU in Berlin, measured (by pupillary reactions) the emotional impact of littering in the public space: "Contrary to what the experts thought until then, this seemingly minor offence triggers a strong reaction in the observer of this offence. Violating social norms or our values provokes a strong feeling of injustice. This could be used as a driving force for behavioural changes and confirms the potential of prevention actions." Therefore, prevention is a powerful lever against the vicious circle of always cleaning up more.

Street furniture and its optimal use is also one of the most effective preventive measures. A comprehensive study by Dr Rebekka Gerlach on the characteristics, causes and prevention of littering confirms the fact that street trash bins are the most effective means of controlling litter (1).

On the other hand, placing trash bins on every street corner is not enough to improve cleanliness. We will show through the experiences of some cities and the Geneva Clean City Lab, how an approach based on data-driven measuring of cleanliness can significantly improve the efficiency of waste bins.

Urban appearance or efficiency of litter bins

In Europe, public waste receptacles are part of urban furniture. However, their integration into urban architecture varies greatly from one city to another. For example, some touristic cities try to hide them so as not to make their squares look ugly. However, for waste receptacles to fulfil their role they must be visible and their function must be well understood.

In Cologne, the University of Humboldt characterised the impact of bin visibility on the level of cleanliness, measured by a DSQS cleanliness index from 0 (clean) to 30 (dirty) (2). Adding a coloured strip to make the bins more visible improved the cleanliness index from 9.7 to 8.6. Reinforcing the message with posters further improved the level of cleanliness (DSQS of 7.4). The city of Annemasse in France replicated this experiment with brightly coloured litter bins. Although the effect was not measured quantitatively, the cleaning services observed a decrease in the amount of paper, cans and cigarette butts on the ground and an increase in the bins (3).

In a previous article (4), we showed through an experiment by the Geneva Clean City Lab that more visible litter bins with a more obvious ashtray function made it possible to reduce the amount of waste on the ground by half. This improvement in the level of cleanliness can also be translated into time savings for the maintenance of the bins. For example, the time required to clean the tram stops where the bins were installed was reduced from 7 to 4 minutes. This characterisation of the maintenance effort at public transport stops revealed potential for improving the ergonomics of the bins. The bins were modified accordingly to make the work of the staff member easier and the bag changes faster. The maintenance time per stop was reduced to 3 minutes, which means a time saving of more than 50% and less work.

There are other potential improvement measures that have been identified but not yet addressed. For instance, the system of fixing the waste receptacles to the ground by bolts makes cleaning around the bins difficult, or stains caused by leachate from the damaged bags are hard to clean. It is therefore very important to take into account the integration of city furniture into the urban architecture, the efficiency of its function, its ergonomics and maintainability at the time of choosing. Small-scale tests allow these issues to be addressed before deploying the equipment on a large scale. The characterisation of the quantities of waste and of the time required for maintenance allow us to make consequent choices.

What is the optimal number of trash bins in a city?

The AVPU (Association des Villes pour la Propreté Urbaine) reports that in France there is on average one litter bin for every 135 inhabitants (5). Its German counterpart, the VKU (Verband Kommunaler Unternehmen), reports the presence of one bin for every 129 inhabitants (6).

Some communities are opting to add more and more waste bins to make the public space cleaner. A survey conducted by Meslard-Hayot and Moreau in 20 French cities in 2019 shows that of these 20 cities, half were considering reinforcing their network of street bins by installing new public waste receptacles. For instance, the city of Nice went from 1,800 to 4,200 garbage cans between 2008 and 2016 (7, 8).

Increasing the number of litter bins does not necessarily lead to less waste on the ground. Laurent Calatayud, head of urban cleaning in Nice: "Having upgraded the litter bin stock, we are now approaching the issue differently. Indeed, the litter bin should be considered as an integrated piece of furniture in a shared urban space. With our Cleanliness and Sustainable Development Observatory, we measure the quantities of waste on the ground to analyse whether the location of the litter bin is appropriate and whether it is fulfilling its role. We have found that in many sectors, by positioning them better, we can reduce their number while maintaining an equivalent level of cleanliness, or even higher in some cases." Moreover, a strategy has been favoured by some French cities such as Vieux-Boucaud, Rennes, Cherbourg, Le Porge, Saint-Hilaire-de-Riez and Nevers. According to Jean-Pierre Auge, director of operations in Nevers, quoted in the study (7): "The multiplication of bins is not a guarantee of greater cleanliness. With half as many and a better will, and with more education, we will do better."

It is therefore above all a question of having visible and well-placed litter bins. Franck Volpi, deputy head of the city of Geneva's urban cleaning department: "With the Clean City Lab, we were able to demonstrate that the new litter bins we designed were twice as effective as the previous ones. We will gradually replace the current pool of 2,000 litter bins, accompanying this change with measurements of the level of cleanliness. Our objective is to reduce the number of litter bins by a third." This approach of placing street furniture according to the degree of soiling has already borne fruit in the case of ashtrays for the town of Montreux (4).

Several factors influence the correct positioning of litter bins. As Franck Volpi mentions, the first is the rate at which a place gets dirty. Secondly, the reachability of the litter bin by users. According to the study by Humboldt Universität ZU Berlin (1), most waste is thrown away within a radius of 2 to 50 metres of a litter bin. The proportion of litter observed directly around the bin is 5% and increases for distances of 2 to 10 and 11 to 50 metres to 36.4% and 37.6% respectively. Finally, there are "hot spots" — areas that seem to attract bad behaviour and litter. Among them, waste collection points are often critical and require special attention, such as dedicated prevention measures or adapted containers.

How does better litter management reduce the need for resources?

Waste bins can significantly improve the cleanliness of streets. To be effective, these litter bins must be kept clean and not allowed to overflow. The maintenance of public trash bins represents a very important cost for the community. Significant resources in terms of vehicles and personnel are dedicated to emptying the public waste receptacles. As we have seen previously, investment and maintenance costs can be significantly reduced by reducing the number of litter bins, for an equivalent or even better level of cleanliness.

At the Clean City Lab, we wanted to measure the potential for optimising bin emptying rounds. To do this, we developed an application for smartphones that allows the agent to enter the rate of filling of the bins, to indicate whether the bag is changed and to report any problems by taking photos (it was these photos that confirmed the importance of dealing specifically with "hot spots"). We carried out ten days of measurements in the experimental area (Louis-Favre district of Geneva). The results showed an average filling rate of 40% for the litter bins. The officers almost systematically change the bags when they pass by and the results show only 15% of the changed bags were more than 50% full.

The results of this study show that it is possible to make substantial savings on the management of waste bins. First of all, changing only the bags that are more than half full could reduce the number of changes by a factor of 6 and save tens of thousands of plastic bags each year. The optimisation of the collection rounds based on the recorded data would also save resources in terms of personnel and machines. In this sector, the potential savings have been estimated at 85% (note: there are no results available yet as the introduction of these changes was delayed until after the introduction of the new street litter bins).

Towards a more efficient approach for street bins

The experiences gathered in the field provide a framework of steps for deploying street bins in order to optimise their impact on cleanliness, investment and maintenance costs. Rather than a recipe, we propose an approach based on experimentation and measurement in representative cases before scaling up to city level.

• Choice of street furniture and prevention measures: In our cities, the street bin is part of the urban environment. It must be visible, engaging, and its function (especially for the ashtray) obvious. Before a wider deployment, the optimal model should be chosen based on cleanliness measurements in a few representative situations. Dirty or overflowing bins will have the opposite effect to that intended.
• Communication — through information campaigns or nudges — reinforces their effectiveness.
• Ease of maintenance is another aspect to consider. Rather than a checklist of points to comply with, an experimental approach that involves staff has shown significant potential for gains, for example in terms of the ease and time required to maintain the bin and its surroundings, and reduced physical strain.
• Define the number of bins and their locations: Well-chosen bins placed in the right locations can significantly reduce the number required. Cleanliness measurement guides the definition of optimal quantities and positions. It may be necessary to rethink the waste management concept in certain locations where the existing infrastructure is insufficient to meet demand.
• Optimise the management of the bin stock: Measuring the filling rate of bins makes it possible to optimise the frequency and duration of emptying rounds. These measurements also make it possible to validate whether the stock meets actual needs. For example, the question should be asked whether to maintain certain bins that fill up slowly.

This field experience has yielded quantified results, revealing the potential for improvement. The approach is easily replicable and would undoubtedly lead to equally significant improvements in other contexts.

Towards cleaner and more sustainable cities

Preventive measures are an important component in keeping cities clean. Urban equipment, reinforced by awareness-raising, has a key role to play. Increasing the number of litter bins does not generally improve cleanliness. The effectiveness of the litter bin must be taken into account: its performance in responding to the correct behaviour of users, its integration into the urban space, its ergonomics and its maintainability. Then they have to be positioned in the right places. The improvement of "hot spots", such as collection points, must be specially addressed.

The "cleanliness measurement" makes it possible to identify the optimal locations, to objectively measure whether the level of cleanliness has been improved and, if not, to correct it. In the end, fewer litter bins mean fewer investments and lower operating costs.

The optimisation of routes also offers potential for improvement, at least in the experiment we conducted as part of the Geneva Clean City Lab. The data collected by a simple application can substantially reduce the consumption of plastic bags and the time taken to empty them, sparing the environment, street cleaning staff, and city users alike.

Optimal management of street bins is beneficial at every level: it engages a virtuous dynamic, preserving resources, costs and a sense of self-esteem for all users of urban public spaces.

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