Any site where waste materials are disposed of by burial. Essentially large holes in the ground, they are used primarily for dumping household and commercial waste, eventually forming artificial hills or mounds as more and more layers are added. Historically this has been the preferred method of waste disposal in many countries, including the UK and the USA, and it is still the most common approach worldwide. However, the sites can be dangerous, producing hazardous decomposition products, and the policy is itself wasteful in terms both of the materials dumped and of land usage. Increasing political sensitivity to environmental issues and the development of commercially viable recycling processes have significantly reduced the use of landfill, especially in developed countries.
Decomposing organic matter releases methane, which can be explosive, although many sites collect the gas and burn it to generate electricity. Many of the items found in landfill sites, for instance bottles, tins, and cans, will remain intact for hundreds of years, and would be better re-used or recycled.
In 1999, the European Union introduced the Landfill Directive, which segregated the types of waste that could be land filled into hazardous, non-hazardous, and inert, restricting each landfill site to one type of waste and introducing strict requirements for the pre-treatment of waste materials ending up in landfill.
A 1990 Canadian study used a plasma torch to reduce landfill rubbish. At the high temperatures used rubbish does not burn but dissociates in a process called pyrolysis. The rubbish mass was reduced by 80%, and its volume by 99%. The process is now used commercially, primarily as a method of converting hazardous waste into non-hazardous materials. It can also be used to convert carbon-based waste materials into fuel gases.
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