Waste management alternatives
Every day your waste is managed as discreetly as possible. Different managing alternatives can be applied to it, depending mainly on its characteristics. Between the most important waste treatments, we can find sorting and recycling, composting, energetic valorisation or landfilling. You can find here a little explanation of these processes, so you know what happens to your waste when it leaves your street in the waste collection vehicle.
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Sorting and recycling
Sorting and recycling allows the recovery of raw materials, which can be later used to manufacture new products.
Consumers are asked to sort their waste using different refuse binds. That facilitates the work of the sorting centre staff.
Two types of waste are accepted at the sorting centre:
- Household waste: packaging (glass, plastic, aluminium, cardboard and steel) as well as newpapers and magazines…
- Commercial and industrial waste: card, paper, wood, metal, plastic, building site waste…
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Once the waste arrives at the centre, it takes place an initial pre-sorting and a first phase of mechanical sorting. After that, a manual process is applied and material is separated in two different groups:
- Reusable material
- Non-recyclable material, which is normally sent to incinerating facilities where it is recovered to energy.
Reusable material is packed and sent either to recycling facilities or they are supplied to industry for reuse (for example, card for the paper industry, plastic for manufacturing piping, etc).
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Sorting waste not only contributes to saving natural resources, but also provides citizens with the reassurance that the waste they sort in the home is indeed sent back to the relevant industry for recycling.
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Composting
Composting is a process that has always existed in its natural state. Today, with modern technologies, this process can be accelerated and monitored efficiently.
It is an excelent way of regenerating soils impoverished by intensive farming.
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Four types of waste are accepted in the composting facilities:
- Waste from the wood industry (bark, shavings), the paper industry and the food industry.
- Farming waste: manure, mineral fertilisers, etc.
- Household waste (food, garden).
- Sludge from the sewage plants.
At the composting facility, the arriving waste is sorted, broken up and disposed in piles in the appropriate conditions for the process to take place.
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Composting is a process based on the decomposition of organic matter by microorganisms in the presence of oxygen. The result is a stable organic product, which is both hygienic and rich in humus. This process, which normally takes several months, can be speeded up and controlled using various techniques.
Once the composting process is finished a product called compost is obtained, which is mainly used for agriculture manure.
Energy from waste
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Nowadays, energy recovery goes hand-by-hand with waste elimination. There are different ways of getting energy from waste: incineration, gasification, anaerobic digestion,…. Traditionally, the most used one has been incineration, although the other treatments are emerging technologies that are being quickly extended. Incineration allows obtaining energy at the same time that the volume of waste is reduced, as well as the use of landfill. The high combustion temperature makes it possible to recover energy from the waste and use it for heating, industrial applications and electricity production. |
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Three different kind of waste are accepted in an incineration facility:
- Household waste
- Non-hazardous industrial waste
- Rejects from sorting centres
In the incineration process, waste collection vehicles dump the waste in vast trenches where it is mixed and transferred to an oven. The waste is then burnt at temperatures reaching 1000°C, producing steam that turns turbines, which in their turn produce electricity. The fumes produced in the combustion are treated by a dry or wet method. Ashes can be reused in civil engineering.
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In the anaerobic digestion process, the organic portion of the waste is separated to remove plastic, glass and metals and then placed in a sealed reactor. The process is similar to the one that occurs naturally in landfills. In the reactor, the conditions necessary for biological degradation are created which allows the production of biogas, that can be used as a fuel to produce electricity.
Landfills
Waste that can neither be reused nor receive special processing is stored in landfills. Beforehand, some waste may need to be stabilised to prevent pollution leakage.
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A landfill requires high technical standards and must conform to strong safety norms in order to protect the environment and local communities. It is very important taking into account:
- The location for the landfill and the surrounding land
- The design of modular compartments
- The protection of groundwater
- The collection, treatment and elimination of leachates
- The capture, treatment and recovery of biogas
- The construction of a cover, in order to minimise rainwater penetration
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Waste is monitored and weighed as it enters the site. Waste with high pollution levels and toxic waste is redirected to a specialist site. Waste is stored in isolated independent cells and then covered with geological screens in the form of layers of impermeable materials (eg clay) topped with watertight and drainage systems. By this way all contact between the waste and the natural environment is prevented. Finally, with the view of revegetation it is added a layer of topsoil.
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Over time, waste, which decomposes produces landfill gas or biogas, a mixture of carbon dioxide and methane. Biogas is collected and then used in co-generation processes, which produce energy and heat, at the same time that it is avoided the emission to the atmosphere of methane, which is a harmful green house gas. In this context, the MICROPHILOX project would develop an innovative process for the use of biogas as a renewable energy to produce electricity and heat. |
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Apart from biogas, the decomposition of landfilled waste, along with rainwater infiltration, produces a liquid known as "leachate". Leachates contain heavy metals, salts, nitrogenous compounds and various types of organic matter. Due to its high polluting potential it is needed that this leachate is collected and treated to avoid environment contamination. In the framework of the LIFE-Environment program, it is being carried out a project called CLONIC, lying in the development of a innovative biological leachate treatment that will improve existing treatments.
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