LANDFILL WASTE DISPOSAL
The landfill site—essentially an enormous hole in the ground (or more accurately a natural depression since sites are not generally excavated first)—is the main alter- native to the technologies discussed in this chapter as a means of waste disposal. Though crude, its simplicity has led it to become the favored method of urban waste disposal across the globe. Waste that has been collected is simply off-loaded at the site until the depression or hollow is considered full. At that point earth is bulldozed over the deposited waste and the whole structure is left to settle. Over time the organic material within the site will decompose, producing carbon dioxide if there is air present but methane if the decomposition takes place in the absence of air. Methane is a common product in many landfill sites and its production can continue for one to three decades after the site has been closed and sealed.
While landfill use remains popular in many countries, it is coming under pressure in others. This is partly a result of the demand for land that increasingly restricts that available for waste burial. More potent still are environmental con- cerns about the lack of recycling and the long-term effects of landfill disposal— effects resulting from the methane emissions from such sites and from the seepage of toxic residues into water supplies.
Such concerns have already led the EU to legislate1 to restrict the use of landfill
waste disposal. Where it does not already exist, similar legislation can be expected in other parts of the world. But waste will still be produced. This is where techno- logical solutions such as the power-from-waste plant enter the equation.
Power-from-waste technology is not cheap. The specialized handling that waste requires, coupled with the need for extensive emission control systems to prevent atmospheric pollution, make such plants much more expensive to build than any other type of combustion power plant. They are also expensive to operate.
If these plants had to survive on the revenue from power generation alone, they would never be built. Fortunately, they have another source of income. Since waste has to be disposed of in a regulated manner, waste disposal plant operators can charge a fee—normally called the tipping fee—to take the waste. The tipping fee represents the main source of income for a power-from-waste plant. Any additional income derived from power generation will benefit the economics but the plant may well be able to survive without it.