Effective recycling relies heavily on effective sorting. There are a wide range of sorting techniques on the market and here we review the five most common. But before we look at the different technologies, let us take a look at the different legislation controlling this growing industry. Organisations that are operating in the EU are bound by EU rules and regulations relating to the environment.
Legislation states that 50% of all household waste and 70% of all construction waste must be re-used or recycled by the year 2020. This looked like a huge challenge when first introduced, but as the introduction of new technology has aided this industry, so commentators believe it is achievable.
The industry consensus is that efficient separation of the different elements found in waste is essential for enabling the recovery of useful recyclable materials, This minimizes the amount of waste sent to landfill and allowing recyclable materials to be re used. Companies sort and recycle materials in order to extract value, so the need to make sure sorting processes are as effective and economical as possible is of huge importance.
Waste disposal companies involved with dealing with the sorting of waste materials will commonly use one of these five methods:
• Trommel screens or drum screens: These machines separate materials according to their particulate size. Raw waste material is fed into a large rotating drum which is perforated with holes of a certain size. Materials smaller than the diameter of the holes will be able to fall through, but larger particles will remain in the drum. Changing drum sizes can further separate the waste.
• Induction sorting: material is sent along a conveyor belt with a series of sensors underneath. These sensors locate different types of metal which are then separated by a system of fast air jets which are linked to the sensors.
• Eddy current separation: this method is used for the separation of metal types. An ‘eddy current’ occurs when a conductor is exposed to a changing magnetic field. Basically, it is a magnetic way of dividing ferrous and non-ferrous metals.
• Near infrared sensors: When materials are illuminated they mostly reflect light in the near infrared wavelength spectrum. The NIR sensor can tell the difference between different materials by the way they reflect light.
• X-ray technology X-rays can be used to distinguish between different types of waste based on their density.
Manual Sorting: It should also be mentioned that manual sorting of waste is still very much a technique that is used in the world today.