Land raising is where pre-dug holes in the ground are filled with rubbish. Landfill on the other hand has the bottom of the pit lined with layers of compacted clay or high density plastic, which is a major advantage in reducing leachates. The waste is then compacted by soil to prevent vermin, stop odours and is capped by clay to seal the landfill. The waste is also compacted to stop air pockets and methane build up, and to decrease subsidence. A further advantage is that rainfall is diverted in pipes around the perimeter of the pit so that rainfall does not cause leachates. Also methane is collected as this causes air pollution and the possibility of explosions but can be used as a fuel for heat and power. However large amounts of carbon dioxide and toxic gases are produced and released into the atmosphere. This could be limited by reducing the amount of organic matter in landfill (composting) but at the present time this is not the case.
The main limitations of landfill are the outbreaks of fires due to gases building up, subsidence and the smell. Furthermore, the amount of lorries to and from the site causing large volumes of noise, congestion and the burning of fossil fuels and taking up space that could be used for agriculture. Conversely there are possible uses of a landfill after use such as recreational uses like golf courses and areas of wildlife refuge as these will not be heavily used and will not cause subsidence.
Ultimately, landfill does provide a cheap way to dispose of large amounts of waste however sites are visually obtrusive and can cause pollution issues if not maintained and managed correctly.
Incineration is a waste treatment technology that involves the combustion of organic materials and/or substances. Incineration and other high temperature waste treatment systems are described as "thermal treatment". Incineration of waste materials converts the waste into incinerator bottom ash, flue gases, particulates, and heat, which can in turn be used to generate electric power. The flue gases are cleaned for pollutants before they are dispersed in the atmosphere.
Advantages of this form of solid waste disposal include the generation of electricity and heat that can substitute power plants powered by other fuels. Also, the ash produced can be used in the building industry as breeze blocks.
In densly populated areas, finding space for additional landfills is becoming increasingly difficult, which therefore avoids the release of methane. By incinerating municipal solid waste, a tonne of carbon dioxide is prevented from being released compared to other solid waste treatments such as landfill.
On the other hand, incineration does pose significant disadvantages. The highly toxic fly ash, for example, must be safely disposed of which usually involves additional waste miles and the need for specialist toxic waste landfill elsewhere. Also incinerators emit varying levels of heavy metals such as mercury which can be toxic at very minute levels.
Furthermore, the start up cost of incinerators is high, and requires long contract periods to recover initial investment costs, causing a long-term lock-in. Also, some of the flue gases are not fully filtered casuing dioxines and carbon dioxide to be released into the atmosphere.
All types of waste treatment will have their strengths and weaknesses, however often local communities are opposed to the idea of locating waste disposal systems in their vicinity – “not in my back yard.” But to be sustainable and to reduce pollution, ultimately we should aim to reduce waste, be it by improving waste loops, recycling schemes or awareness to the problems of waste. The waste hierarchy; prevention, waste minimisation, reuse and recycling should always come before treatment of waste in any of its guises.
