Sensor Based Sorting Of Waste
Waste Segregation has become more complex than it was a few years back – it is no longer just paper, plastic, and glass but it contains multi-layer packaging and other composite waste as well. Recycling can only take place when waste is segregated. As the amount of waste keeps increasing the number of people who work in this sector needs to increase. To segregate waste efficiently, companies have developed machines and sensors which properly segregate waste.
Technology has been used in waste segregation since the 1990’s. Near InfraRed (NIR) technology works on the principle of measuring the reflectivity of an object with light ranging from 1,100-2,100 nanometres. In this wavelength range, materials such as plastics, paper, and textiles have their own characteristics. These systems can distinguish between the different types of plastics, and even segregate tetra packs and composite waste properly. However, dark materials, stone, and porcelain cannot be sorted with this as they do not have measurable characteristics in this wavelength range.
Technology used to separate waste includes:
- Trommel separators/drum screens separate materials depending on their particle size using a perforated screen on the drum, allowing only some items to pass through.
- Eddy current separator is an electromagnetic way of dividing ferrous and non-ferrous metals.
- Induction sorting Material is sent along a conveyor belt with a series of sensors underneath which locate different types of metal. The metal is then separated by fast air jets linked to the sensors.
- Near infrared sensors (NIR) When materials are illuminated they mostly reflect light in the near infrared wavelength spectrum. The NIR sensor can distinguish between different materials based on the way they reflect light.
- X-rays can be used to distinguish between different types of waste based on their density.
NIR sensors and sorters are even used in making recycled newsprint. To make this, only de-inked newsprint, office paper, and magazine paper are allowed as constituents. NIR technology and visible light are used in combination by machines to separate out the colored paper, the cardboard, and paperboard are segregated away from the materials that constitute the pulp to make recycled newsprint.
Domestic waste was traditionally incinerated, but is now sorted into e-waste, dry waste, wet waste, and medicinal waste. E-waste contains high-value precious metals, and by using the technological advancements we have made, these metals can be extracted from it and used or sold. Forty-one cell phones contain approximately the same amount of gold that an entire ton of ore from a mine does. Platinum and copper are also found in e-waste. There are companies that extract these metals from e-waste, turning a profit.
Even waste-to-energy plants require segregation; At present most waste for co-combustion undergoes little or no sorting to remove chlorine from the waste, leading to higher greenhouse gas emissions and the furnaces burning the waste undergo corrosion due to the co-combustion. Also, sorting of batteries to remove Nickel Cadmium-batteries is currently carried out by hand, which is inefficient, slow and causes unhealthy working conditions. Sensor based sorting could improve the power produced per tonne of waste, reducing the CO2 emissions and lead to improved recovery of Nickel Cadmium-batteries.
The use of sensors in the segregation of waste is expensive; it requires a large initial investment. The cost starts at around 90,000 INR for one Near InfraRed sensor alone, and implementing this on a large scale will be expensive. However, the social cost of manual sorting is extremely high. Illegal waste pickers sort through the waste, picking out the recyclables with bare hands and not wearing any protective gear. The risks to their health is high and many of them cannot afford proper healthcare. Thus, starting the use of sensors in segregation facilities will greatly help reduce the social impact of recycling. The use of sensors will cause increase in jobs in the waste segregation sector, since more people are needed to bring in the change which will impact our environment in a positive way.
While sensors have not been utilized in Bangalore yet, there are apps that link the waste workers to certain houses and rate the level of waste segregation that already takes place in those households.
Automatic waste segregation is an idea with great potential and is a breakthrough in waste management:
- Waste separation technology is a breakthrough in waste recycling industry, because it can enable us to fully recycle the municipal waste.
- It does no harm to the environment. It can recycle harmful waste like waste battery, avoiding water and soil pollution.
- Using the automatic sorting machine can avoid the secondary pollution caused by burning and land filling.
- It can achieve the cyclic utilization of waste. Useful materials obtained after processing of waste can be extracted and used.
- Plastic waste can be converted into oil by using waste plastic pyrolysis plant.
- The sorted organic waste is good material to make natural fertilizers.
- Soil and waste bricks in waste can be utilized in the making of bricks.
Automated waste sorting is expensive, and not developed enough to use at the moment. The development of this method is essential for proper waste segregation to take place. Workers who segregate it manually need to rely on their vision and experience with different materials. Machines, on the other hand, rely on data and the properties of the material, making them more efficient as compared to manual segregation. A concern that arises is that there will be a loss in employment opportunities for people who relied on waste segregation for their livelihood. However, the installation of these sensors and their operation requires people, and thus creates more jobs. Also, due to the cost of these sensors, they cannot be installed everywhere and will not cost many people their jobs. Those that do lose them can operate the equipment or help in its installation. Therefore, development of these sensors, and making them efficient and high-quality, is essential and will help in the long run, making recycling a more prominent industry and help the environment simultaneously.
- ETtech.com. “App to Drive Garbage Separation in Bangalore – ETtech.” ETtech.com, 15 Dec. 2016, tech.economictimes.indiatimes.com/news/technology/app-to-drive-garbage-separation-in-bangalore/55992096
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- “With New Technologies and Knowledge of Segregation, India Is Fast Learning How to Manage Its Waste.” The Economic Times, 21 May 2017, economictimes.indiatimes.com/news/politics-and-nation/with-new-technologies-and-knowledge-of-segregation-india-is-fast-learning-how-to-manage-its-waste/articleshow/58766783.cms.