City dwellers generate two to three times more trash than their rural counterparts, mainly due to increased consumption of pre-packaged goods. In a world expecting to see more than 5 billion - two out of every three people - living in urban areas by 2030, already strained municipal waste management systems will be hard pressed to cope. Developed countries are running out of space to contain growing volumes of consumer discards, while developing countries lack appropriate systems and infrastructure to service their populations. In many parts of Africa, Asia and Latin America, informal garbage collectors clear more refuse than do municipal employees.
Historically, cities have dumped, burned or buried their waste. Dumping and burning are widespread in places with poor collection and sanitation services, particularly in slums and squatter settlements. Lacking proper facilities, residents have no other option but to dispose of their waste as best they can: usually burning flammables and tossing the rest into rivers, ditches or streets. Uncontrolled decomposition of food and human waste helps spread diseases like diarrhoea, typhoid, cholera, dysentery, tuberculosis and malaria, while fumes from open fires damage lungs and release harmful pollutants into the air.
In wealthier areas, residents pay for garbage removal to landfills and incinerators, both of which can cause human and environmental damage through groundwater contaminants, emissions of methane (a greenhouse gas) and cancer-causing dioxins. And while conscientious citizens often choose to recycle, public apathy and high operational costs can diminish the effectiveness of these programmes.
In 2000, the world's people produced 12.6 billion tonnes of waste, more than 2 tonnes for every one of us; by 2050, we will face a projected 26.7 billion tonnes each year, nearly 3 tonnes per person. Unprecedented volumes of paper, plastics, textiles, cardboard, glass, metals and organic mass - just to name a few - will need to be got rid of somehow.
Fortunately, scientific advances and the application of common sense can help to reduce and reuse the messes we create.
Clean power plants already operate in Brazil, Argentina, Chile and Venezuela, turning biomass (plant and organic matter) into electricity for over 5 million customers.
In the United States, more than 6,000 cities have adopted Pay-As-You-Throw programmes that charge residents based on the number and sizes of trash containers collected. By increasing the cost of garbage disposal and keeping recycling fees low or free, cities like Falmouth, Maine and Mount Vernon, Iowa, have seen solid waste decrease by more than 35 per cent. Dover, New Hampshire, reduced annual waste by over 7,000 tonnes for eight years running after switching to the scheme, and increased recycling levels more than 50 per cent.
Even soiled nappies can be remade into useful items through clever technology. Knowaste, a New York-based company, runs two processing facilities in Arnhem in the Netherlands and Santa Clarita in California, USA, that separate and sanitize the plastics, wood fibres and super absorbent polymers contained in them. These raw materials are then sold to manufacturers for reincarnation as shoe insoles, roof shingles, oil filters and wallpaper.
From state-of-the-art procedures to simple innovations, solutions for waste management exist. A few have been adopted quickly, while others may take some getting used to - as Ethiopian Almaz Terrefe can attest. Her home-grown vegetables certainly are tasty, yet in seven years she has only attracted about 300 other people to try her organization's system of food production through ecological sanitation - using treated human waste as fertilizer
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