Combining primary collection with decentralised composting - a solution?
The environmental problems of urban areas extend over a wide range of spatial scales; i.e., the household, the place of work, the neighbourhood, the city, the wider region, and the world. In rapidly growing cities of the developing world, urban solid waste management (SWM) is currently regarded as one of the most immediate and serious problems faced by urban governments. Inadequate or unavailable solid waste collection and services result in indiscriminate dumping of waste on streets and public areas, clogging of urban drainage systems, contamination of water resources, and proliferation of insect and rodent vectors. Such conditions increase health risks by direct human contact with solid waste, and constitute major factors in the spread of gastrointestinal and parasitic diseases. Even if the efficiencies of existing collection systems are improved significantly, a large section of the population will realistically not be served by municipal services, especially in low-income areas where insufficient pressure is exerted on municipalities to provide the necessary services. In other words, residents of low-income areas have to manage their own waste and develop alternative waste collection systems adapted to their economic needs.
Aside from the difficulties associated with waste collection, many municipalities are also responsible for the final disposal of solid waste. Inadequate disposal, often through uncontrolled dumping, poses a serious health risk to the population concerned and constitutes a major cause of environmental degradation in most cities of the developing world. Numerous dumps or landfills have almost reached their maximum filling capacity, and new sites are increasingly difficult to find or are located far from the collection areas, thereby, leading to high transport costs. One way to improve this state-of-the-art is to promote resource recovery. Recycling of different materials from municipal solid waste is often a well-functioning activity conducted by the informal sector. However, organic waste material, which often makes up more than 50% of the total waste, still has an important recovery potential. From the perspective of solid waste managers, organic waste recycling not only reduces disposal costs and prolongs the life span of disposal sites, but it also reduces the environmental impacts caused by the sites, as the organics are mainly responsible for leachate contamination and methane problems. In many parts of the world, solid waste managers are, therefore, exploring ways to reduce the flow of biodegradable materials to landfills. Moreover, recycling and returning of organic waste to the soil will significantly contribute to enhancing the sustainability of the urban world. Involving the population in the use of compost promotes awareness of the waste resource recovery and composting activities, creates employment and generates income.
The interest in composting plants grew world-wide and became quite popular in the 1960s when manufacturers offered large-scale and highly mechanised plants (Alter Ego et al., 1996). The reason for promoting such largescale and highly mechanised plants was to reduce the production costs through an economy of scale and to produce a standardised product of high quality. Plant manufacturers convinced national governments, particularly in developing countries, that composting and the produced organic fertiliser would solve their disposal problems. Since performance of most of these capital-intensive, large-scale and highly mechanised composting plants built in cities of developing countries in the 1960s-80s was poor, production was often stopped shortly after start up, in almost all cases long before the plant's depreciation time. Such composting projects turned out to be serious financial failures for the governments, and composting as such therefore lost its reputation irrespective of the technology applied.
This paper presents a pilot project initiated by SANDEC and Yayasan Dian Desa in Yogyakarta, Indonesia. Main focus of the project was placed on small-scale decentralised composting operated by a community-based primary waste collection service. The objectives of the project were to encourage low-income urban communities to manage their own waste collection, to integrate resource recovery and recycling into their collection scheme, and also to gain experience with such systems for replication in other communities.