| An Urban Waste Management Continuum: From Disposal to Minimization |
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A rising quality of life, and high rates of resource consumption patterns have had a unintended and negative impact on the urban environment - generation of wastes far beyond the handling capacities of urban governments and agencies. Cities are now grappling with the problems of high volumes of waste, the costs involved, the disposal technologies and methodologies, and the impact of wastes on the local and global environment. Most local governments and urban agencies have, time and again, identified waste management as a major problem that has reached proportions requiring drastic measures. We can observe three key trends with respect to solid waste - increase in shear volume of waste generated by urban residents; change in the quality or make-up of waste generated; and the disposal method of waste collected, by land-fill, incineration etc.
But these problems have also provided a window of opportunity for cities to find solutions - involving the community and the private sector; involving innovative technologies and disposal methods; and involving behaviour changes and awareness raising. These issues have been amply demonstrated by good practices from many cities around the world. There is a need, therefore, for a complete rethinking of "waste" - to analyse if waste is indeed a 'waste'. The current emphasis on waste disposal that is focused on municipalities and uses high energy/high technology, needs to move more towards waste processing and waste recycling that involves public-private partnerships, eventually aiming at waste minimization, driven at the community level, and using low energy/low technology resources. Some of the defining criteria for future waste minimization programmes will include deeper community participation, understanding economic benefits/recovery of waste, focusing on product life cycles (rather than end-of-pipe solutions), decentralized administration of waste, minimizing environmental impacts, and reconciling investment costs with long-term goals. The above four key aspects of waste management – disposal, processing, recycling and minimization – is laid out here in the form of a dual-axis continuum (see Figure 1), which will help us in understanding the actors to be involved and the actions to be taken, and in building a comprehensive waste management strategy for local governments and other stakeholders in cities of developing countries.
Historically, efforts in the management of waste have focused primarily on the disposal part of the waste management. Whilst local governments are now moving towards recovery of resources from waste, disposal is still the most common form of managing waste, including open dumping, landfilling of waste and incineration. In developing countries, infrastructure for waste management may be limited, and waste is often left uncollected or disposed of in inappropriate locations, leading to significant environmental and public health problems. For example, in India, the Yamuna river, which flows through Delhi, is heavily polluted due to the dumping of untreated waste and sewage. In Nairobi, Kenya, the Dandora landfill site, which was opened in the 1970s, has become a symbol of environmental degradation and pollution due to the lack of proper management and regulation. Landfilling of waste is also carried out in places where land is available. In many cases, these landfills are unfortunately poorly designed and operated, resulting in environmental pollution and health hazards for the communities living near them. For example, in the Philippines, the Payatas landfill in Quezon City, Manila, is one of the largest landfills in the country, but it is also notorious for the large number of waste-related accidents and illnesses that occur in the area. Some developing countries have also set up incineration plants to dispose waste. But incineration plants are poorly regulated and operated, resulting in significant emissions of toxic pollutants. For example, in Bangladesh, the Amin Bazar incineration plant, which was built to dispose of medical waste, has been found to emit high levels of dioxins. While waste disposal methods such as dumping, landfilling, and incineration are still widely practiced in many developing countries, there is a growing recognition of the need to move towards more sustainable waste management practices, such as resource recovery and recycling, to reduce the environmental and health impacts of waste disposal.
Waste processing is the range of activities characterized by the treatment and recovery (use) of materials or energy from waste through thermal, chemical, or biological means. It also covers hazardous waste handling. Generally, there are two main groups of processes to be considered, (1) Biological processes, such as open composting, enclosed composting, anaerobic digestion, and vermiculture, and (2) Thermal processes, such as incineration, and gasification. Examples of reuse in initiatives include: (1) Product reuse - rethreading tires, recovery of demolition materials, reuse of plastic bags, second hand clothing, reconditioning and repair of furniture and appliances; (2) Materials reuse - Liquid-paper board for seedlings planters, bottles, scrap paper for notes/phone messages, mulching; (3) Durable packaging - e.g. milk crates, bread trays, string or calico shopping bags.
Recycling is the breaking down of materials from waste streams into raw materials, which are then reprocessed either into the same material (called a "closed loop" system for resource recovery) or a new product (or an "open loop"). Recycling also generally includes waste separation and material reprocessing. There are various materials that are capable of being recycled - most common being paper, plastic, glass and metals - and technology is advancing to allow the recycling of more materials. Some examples:
Waste minimization is aimed at reducing the production of waste through education and improved production process rather than aiming to increase technology to improve treatment of waste. The idea of minimization is not centered on technological advances, it can be viewed a method of managing existing resources and technology in order to maximise the efficiency of available resource use. Minimizing waste generation has the potential to reduce costs or increase profits by maximizing the use of resources and by reducing the amount of waste to be disposed of the cost of waste management is also decreased. Waste avoidance for individuals: Buying goods in bulk; reconsidering superfluous purchases; purchasing products in materials/packaging that is readily recycled; use of alternatives, e.g. landscaping that creates mulched gardens in place of lawns; and use of composting and vermiculture practices. Waste minimization in industry: Change in product design to reduce materials consumption; using crates instead of pallets to avoid the need for shrink wrap; incorporate Eco-Design technology into production processes; adoption of Cleaner Production practices that ensure avoidance through efficiency measures; and conduct regular audits and monitoring of waste reduction/resource recovery practices. Waste minimization for Local Government: Encourage community 'avoidance' activities, e.g. promote competitions rewarding initiative in this area of resource recovery; lead by example, e.g. display mulched gardens throughout the municipality; and provide facilities and infrastructure to assist industry, business and the community to undertake resource recovery practices, e.g. kerbside recycling and resource exchange registers, initiate greener procurement programmes. Some examples:
Taken together, the four issues of waste disposal, recycling, processing, and minimization, can be laid out on a dual-axis continuum as illustrated in Figure 1.
 Figure 1: The Waste Management Continuum The Waste Management Continuum has two axes. One is the horizontal axis that lays out the different stakeholders involved in waste management - ranging from municipalities and local governments to the local neighbourhoods and communities. The other is the vertical axis that lays out the different technologies used in waste management - ranging from high tech/high energy disposal systems to low tech low energy systems. Much of current waste management efforts is focused on local government programmes that use high tech/high energy disposal systems (the 'NOW" position in the continuum). Waste management systems need to move towards a scenario that is more community based using low tech/low energy, and focused on waste minimization. In achieving this goal, we also have to pass through the two 'gray' areas of waste processing (treatment and recovery of waste to recover materials or produce energy from waste) and waste recycling (breaking down of wastes to facilitate their reuse into new products). The continuum helps us understand the different systems of waste management currently practiced in different countries, and the pathways that will lead to an "ideal" situation where waste is minimized and materials are recovered and recycled back into manufacturing systems. The two axes of the continuum also illustrate important aspects of waste management systems -
The current systems of waste management use the opposite - high tech systems that need considerable amounts of energy to dispose wastes. The continuum illustrates the point that we need to focus more on waste minimization that uses low levels of technologies (for example easy disassembly of products to their constituent raw materials, and not use composite materials) and can be carried out by local communities themselves (for environmental reasons, but more so for economic opportunities).
Ultimately, waste is not just an environmental issue that needs to be "disposed" - but is a broader that has many social and economic dimensions as well. Lifestyle choices and household consumption patterns that help to minimize waste lie at the core of waste management systems - along with better product design, "Design for disassembly" and other issues that facilitate such choices. Ensuring that such systems also provide economic opportunities - additional jobs and increased income - provides the necessary incentives for better waste minization.
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