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Landfill is the disposal of waste into or onto land.
Today, landfill sites are constructed and operated to strict technical standards in order to minimise any negative environmental impact they may have. These standards are strictly regulated by the Scottish Environmental Protection Agency.
Sending waste to landfill leads to a loss of valuable resources. The environment is also affected when we replace the things that we throw away with new products. This is because energy and natural resources are needed to make new items.
The 'waste hierarchy' ranks the different ways in which we can dispose of our waste in order of sustainability. The most sustainable and environmentally-friendly option is to reduce the amount of waste we produce in the first place. However, we also need to continue reusing and recycling as many items as we can.
To reduce the amount of waste sent to landfill, Angus Council diverts around half of the waste from household grey bin collections to Dundee's Energy from Waste plant. Here, the waste is incinerated and used to generate electricity
This is known as recovery.
The remaining waste from grey bin collections is sent to landfill, which is disposal.
Angus Council's landfill site is situated at Restenneth, near Forfar. It has been in operation since November 1998. Since it opened it has received over 650,000 tonnes of waste from grey bin collections and general waste skips at Recycling Centres.
In 2009-10 the site received over 49,000 tonnes of waste.
Prior to becoming a landfill site, the area was used for quarrying activities. By using it as a landfill, and filling in the space dug out by quarrying activities, it allows the area to be restored back to its natural habitat.
Before it can be used as landfill, pockets of land called cells have to be lined with an impermeable membrane. This is to prevent the escape of contaminants into the environment.
Refuse Collection Vehicles containing household waste from kerbside collections, and skip lorries containing general waste from Recycling Centres arrive at the landfill site and drive onto a weighbridge.
This allows us to measure how much waste is being deposited in the landfill.
The vehicle then proceeds to the active landfill cell and tips its load. The waste is then compacted to reduce trapped air spaces and covered with inert materials such as sand, stones and rubble to prevent odour, litter and pest infestations.
The waste will gradually decompose.
While items like disposable nappies, glass bottles and jars and plastic bottles may never completely break down, items like paper, cardboard and fruit and vegetables can decompose in a matter of months. This decomposition process releases leachate and gas.
Leachate is a liquid that is generated by the decomposition of waste and rainwater that has come into contact with waste.
The gas produced is a mix of carbon dioxide and methane.
The leachate produced by the decomposition of waste is very environmentally damaging and if allowed to escape can pollute rivers and underground sources of drinking water.
It arrives at the leachate treatment pools on site, where it undergoes a three day cycle to restore the quality of the water and remove contaminants.
This is the control room for the leachate pools.
On day one, the leachate is dosed with chemicals and heated up to provide a suitable environment for bacteria to break down contaminants.
On day two, the pools are aerated to provide oxygen to allow the bacteria to continue breaking down contaminants. This is why the water appears foamy.
On day three, the leachate is allowed to settle and it is automatically sampled using sensors built into the pools.
Once the leachate has reached a suitable quality it is automatically discharged to Scottish Water's treatment plant, where it is further purified and finally discharged. At this point the water is of a quality equal to drinking water.
Carbon dioxide and methane are both environmentally damaging greenhouse gases produced by the decomposition of organic waste. If allowed to escape into the atmosphere they can contribute to climate change.
At the landfill site these gases are captured and transported through a series of pipes to an on-site electricity generating plant which contributes energy to the national grid. Heat is also generated here, which is used to help the treatment processes in the leachate pools.
When landfill has reached maximum capacity it is covered completely and restored using soils and compost, which has been created from the household garden waste collection
Although most modern landfills are more environmentally friendly than previous ones, they are still one of the least sustainable methods of waste disposal.
Landfills attract seagulls, vermin and flies and can also cause problems associated with odour and noise.
To help combat these problems, Angus Council uses the service of a trained hawk. Foraging birds are a large problem at landfill sites and birds of prey are valuable in deterring them. The hawk is released and circles above the site, scaring away seagulls in the process.
There is also a pest controller who ensures that rats do not become established on the site and cause problems for the site's neighbours.
Many landfill sites are nearly full and it is difficult to find suitable land for new sites. Consequently the UK Government places a tax on every tonne of waste that is sent to landfill. The aim of this tax is to encourage waste producers to produce less waste and use more environmentally friendly methods of waste treatment.
In 2011 the charge for sending waste to landfill stood at £56 per tonne, and will increase each year to reach £80 per tonne in 2014.
In 2008 Scotland produced nearly 20 million tonnes of waste, of which over 6 million tonnes was landfilled. Unfortunately it is not possible to recycle or recover energy from everything just yet, so landfill sites still play a necessary role in managing Scotland's waste arisings.
For more information about waste and recycling please visit www.angus.gov.uk/recycling