Spatial-temporal model for demand and allocation of waste landfills in growing urban regions

Abstract Shortage of land for waste disposal is a serious and growing potential problem in most large urban regions. However, no practical studies have been reported in the literature that incorporate the process of consumption and depletion of landfill space in urban regions over time and analyse its implications for the management of waste. An evaluation of existing models of waste management indicates that they can provide significant insights into the design of solid waste management activities. However, these models do not integrate spatial and temporal aspects of waste disposal that are essential to understand and measure the problem of shortage of land. The lack of adequate models is caused in part due to limitations of the methodologies the existing models are based upon, such as limitations of geographic information systems (GIS) in handling dynamic processes, and the limitations of systems analysis in incorporating spatial physical properties. This indicates that new methods need to be introduced in waste management modelling. Moreover, existing models generally do not link waste management to the process of urban growth. This paper presents a model to spatially and dynamically model the demand for and allocation of facilities for urban solid waste disposal in growing urban regions. The model developed here consists of a loose-coupled system that integrates GIS (geographic information systems) and cellular automata (CA) in order to give it spatial and dynamic capabilities. The model combines three sub-systems: (1) a CA-based model to simulate spatial urban growth over the future; (2) a spread-sheet calculation for designing waste disposal options and hence evaluating demand for landfill space over time; and (3) a model developed within a GIS to evaluate the availability and suitability of land for landfill over time and then simulate allocation of landfills in the available land. The proposed model has been tested and set up with data from a real source (Porto Alegre City, Brazil), and has successfully assessed the demand for landfills and their allocation over time under a range of scenarios of decision-making regarding waste disposal systems, urban growth patterns and land evaluation criteria.