Population growth, urbanisation and growth of consumerism have resulted in increased demand for municipal solid waste disposal. Many countries have implemented measures to encourage households to reduce their waste volumes. Of the various measures, studies have shown that unit-based pricing for waste disposal, or often referred to as Pay-As-You-Throw (PAYT), has significant potential to encourage waste reduction efforts in a cost-minimising manner. Nevertheless, PAYT may not be equally effective in every community with different social context and cultures. Most studies on PAYT have focused on communities with direct door-to-door waste collections. There is limited literature on how PAYT may perform in a high-rise community with indirect collection such as Singapore, where most households live in high-rise flats and waste is disposed of through a common discharge chute on each floor to a central refuse container where it is then transferred to waste collection trucks.
This research seeks to investigate the potential for PAYT in reducing waste in Singapore and the possible behaviours of households in recycling and disposing of their waste if PAYT is implemented. In particular, the research looks into whether households in a PAYT programme are likely to dump their waste illegally or dispose of household waste in public litter bins. The research uses agent-based modelling to simulate the interactions between households and infrastructure (e.g. location of recycling bins, waste chutes, presence of enforcement etc.) and predict possible behaviours of households in a high-rise apartment block. In building the agent-based model, the research uses the Theory of Planned Behaviour (TPB) as the theoretical framework to simulate the waste disposal and recycling behaviours of households. TPB assumes that people behave rationally and recycling behaviour is affected by subjective norm, attitudes and perceived control. In turn, social influence (e.g. whether a neighbour is recycling or dumping his waste illegally) has a significant impact on subjective norm, one of the key factors affecting households’ behaviours.
Results from the agent-based modelling show that the locations of waste and recycling bins or chutes in a high-rise building have an impact on the subjective norm of households which in turn affects their recycling behaviours. Locating both waste and recycling bins on the ground floor instead of having waste or recycling chutes on each floor would result in greater interactions between households and promote recycling. However, the significance of this impact on households’ recycling behaviour diminishes over time. The agent-based modelling also shows that the initial number of households, which would dump their waste in public litter bins, is a significant determinant of whether illegal dumping would become a problem when PAYT is implemented. Results show that it is important to ensure that majority of households do not dispose of their waste in public litter bins in the initial stages so as to avoid illegal dumping from becoming a problem. Results from this research could potentially help policy makers better understand the conditions required for the successful implementation of PAYT.