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Waste Disposal

Some waste can not be recycled or recovered and therefore need to be disposed of either by landfill or destroying the waste through incineration. Waste disposal is at the bottom of the waste hierarchy and is the least desirable method of waste management. Waste disposal is a persistent and ever growing problem. There is an increasing drive towards a more sustainable way of waste management for example, recycling and recovery. Despite this, there will always be need for certain wastes to be disposed of. 


The methods of waste disposal vary according to the materials in the waste, and include Landfill (deposit or burial of waste at a certain site) and Incineration (destruction though burning of waste with or without energy recovery).


Landfill

Landfill as we all know simply involves the deposition or in a more crude term, burial of waste

At its crudest, landfill consists of tipping waste into a hole in the ground, covering it with soil and forgetting about it. Up until the introduction of the Landfill Directive and Landfill tax, the process of landfill was, let say easy and relatively cheap. Historically, this made it the dominant method of waste disposal in the United Kingdom and many other countries worldwide. 


Disposal of waste in a landfill involves burying the waste, and this remains a common practice in most countries. Landfills were often established in abandoned or unused quarries and mineral extraction sites. A properly designed and well-managed landfill can be an environmentally safe and relatively inexpensive method of disposing of waste materials. Older, poorly designed or poorly managed landfills can create a number of adverse environmental impacts such as wind-blown litter, attraction of vermin, and generation of leachate. Another common product of landfills is gas (mostly composed of methane and carbon dioxide), which is produced as organic waste breaks down anaerobically. This gas can create odor problems, kill surface vegetation, and is a greenhouse gas. 

Design characteristics of a modern landfill include methods to contain leachate such as clay or plastic lining material. Deposited is normally compacted to increase its density and stability, and covered to prevent attracting vermin (such as mice or rats). Many landfills also have landfill gas extraction systems installed to extract the landfill gas. Gas is pumped out of the landfill using perforated pipes and flared off or burnt in a gas engine to generate electricity. 


This section aims to look at the processes taking place in a municipal Solid Waste landfill, mainly chemical and biological processes. These processes are responsible for most of the pollution incidents through the discharge of leachates and gaseous products into the environment. We will then consider the design and operation of modern landfill and the techniques used to minimize the risk of the harm to public health and the environment. In this section, we will be looking at the following:


Incineration

Incineration is a disposal method in which solid organic wastes are subjected to combustion

so as to convert them into residue and gaseous products. This method is useful for disposal of residue of both solid waste management and solid residue from waste water management. This process reduces the volumes of solid waste to 20 to 30 percent of the original volume.


In legal terms and as defined by the Environment Agency, Incineration of wastes’ includes incineration in an incinerator and incineration in a co-incinerator. Incineration in an incinerator is when the main purpose of the activity is the disposal of waste. Incineration in a co-incinerator, such as a cement kiln or combustion plant, is used when the main purpose is the production of material products or energy, and waste is used as a fuel. Energy is recovered, ferrous and non ferrous metals are also reclaimed from the residual ash which can be reclaimed as aggregate substitutes. 


The Waste Incineration Directive (now covered by the Industrial Emissions Directive and implemented in the UK by the Environmental Permitting Regulations, 2013) requires that an environmental permit must be obtained before operating such plants. This is to prevent or limit, as far as practicable, negative effects on the environment, in particular pollution by emissions into air, soil, surface and groundwater and the resulting risks to human health, from the incineration and co-incineration of waste.


The directive seeks to achieve this high level of environmental and human health protection by requiring the setting and maintaining of stringent operational conditions, technical requirements and emission limit values for plants incinerating and co-incinerating waste throughout the EU.


Plant operators must demonstrate that they are applying the principles of best available techniques (BAT) to prevent , or where not practicable, to minimize pollution.

Incineration is common in countries such as Japan where land is more scarce, as these facilities generally do not require as much area as landfills.


Energy-from-waste (EfW) are broad terms for facilities that burn waste in a furnace or boiler to generate heat, steam or electricity. Combustion in an incinerator is not always perfect and there have been concerns about pollutants in gaseous emissions from incinerator stacks. Particular concern has focused on some very persistent organics such as dioxins, furans, PAHs which may be created which may have serious environmental consequences.

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