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Overview
The UK alone recycles 752,000 tonnes of glass each year. This saves around 237 million kilograms of CO2 from being released into the atmosphere.
The process of making glass involves melting sand, soda ash and limestone at 1500oC, the use of recycled glass means the energy used to extract these materials can be saved. As a result recycled glass leads to a 20% reduction in air pollution and a 50% reduction in water pollution compared to making glass from scratch. For every tonne of glass recycled 1.2 tonnes of these materials is saved.
The level of waste recycled in the UK is substantially lower than the level of waste placed into recycling bins. 25% of waste put into recycled bins ends up in landfill, a primary cause for this is contamination.
Glass recycling is often overlooked when it comes to contamination in recycling however this should not be the case. Based on the country or even county you live in the glass recycling systems can vary hugely. Some regions require the user to separate by colour whilst others rely on this being carried out at a later stage.
Glass can be 100% recycled with no loss in quality. Glasses ability to be recycled without a drop in contamination is heavily dependant on a lack of contamination. This is because the variation of colour across glass is brought about through the addition of different impurities. Brown (amber) glass is created using carbon nickle and sulfer. These protect the contents from sunlight. Green glass is made using copper, iron and chromium. Clear glass is simply pure sand and limestone. By introducing impurities from a separate colour of glass into the stream the quality of the glass will swiftly diminish.
The Glassify team is building a low-cost system which allows for the effective sorting of bottles of different colours: green, amber and clear. This device is aimed to be installed at recycling points to allow for the separation of bottles at the user-end. The low-cost aspect of the product is achieved by using a Raspberry-Pi, a small computer costing ~£30, which acts as the brain of the system. We are also using standard electric components and utilise 3D printing and PVC piping to build the structure of the system. The overall cost of the device is under £100. 3D printing allows the system to be made to fit any existing recycling bin design with only minor adjustments to it.
The system is triggered by an entering bottle. The built-in camera takes several pictures of the falling glass. Our algorithm rapidly evaluates each snapshot to detect the colour of the item. Once a decision is made, the servo rotates the output chute to the appropriate position and the bottle exits through to the correct bin. The system also indicates the colour of the glass detected as well as allows for the manual calibration of several parameters.