“Humans generated over 2 000 000 000 000 kg of solid waste in 2016.”
Global warming is not the only huge problem facing humans on planet earth. It is no news that the environment is becoming polluted due to our greed and indifference. Oceans are now the biggest single garbage dump on this planet.
Our grandchildren are going to drown in waste, literally, unless we do something. We will survive only after we realize that waste can be turned to money and recycling can be profitable. Objects around us are not disposable but reusable raw material.
There are, however, ways to efficient recycling leading to more sustainable production and consumption. We are fortunate to have the needed technology to turn the course of events and solve many of the key problems in the current industry: material identification, contaminants, and final purity.
Recycling in numbers
Are we exploiting maximum recycling potential and are all materials that are recyclable, actually being recycled? It is true that the amount of plastic, glass, paper, and metal recycled from waste has been steadily rising over the years.
This is a big positive change. Yet many countries are still far from reaching their recycling targets. According to statistics, collected waste percentages in some European countries are surprisingly high, far above 80%. Germany gives “recycling” rates of 67% for household waste, around 70% for production and commercial waste, and almost 90% for construction and demolition waste.
Development of municipal waste recycling stream in EU (%) – Eurostat
This means that waste is not really recycled, and we still need virgin materials like wood and oil to produce new consumables. This matters since the main benefits of recycling are to conserve natural resources like fossil fuels, save in energy and reduce greenhouse gases and pollution. It is calculated that recycling reduces energy consumption by about 70% for plastics, 60% for steel, 40% for paper and 30% for glass. These are high numbers knowing the amount of annual production.
Problems in waste treatment
In most cases, available sorting technology limits the amount of material that can be recycled. Typical waste recycling process includes collection to the recovery facility, separation to different waste streams, basic cleaning and final sorting to classes. The resulting product is then either burned, recycled based on type and purity or placed to landfill. At the moment these recovery or recycling plants use different technologies from barcode readers, RGB cameras to x-ray and eddy current systems. These are capable technologies to some extent but not perfect solutions as they cannot recognize the material itself. For example, in case a plastic bottle is missing its label with printed barcode it is not possible to say if it is PET or HDPE. So-called multispectral technology is helping but is limited to a few basic materials in each sorting location.
It is also a fact that human labour must be used due to inadequate detection technologies. Waste is shipped to lower-cost countries where people are manually sorting materials from conveyor belts. Although this creates jobs, it is by far not the safest and most desirable of professions. It would be beneficial to have robots or other sorting machinery in most places – but a robot needs “visual” aid for material detection.
Spectral camera – state of the art solution
Spectroscopy is the art of measuring the interaction between light and matter. In all matter around us this interaction, absorption, and reflection, is different. All different plastic types, wood, paper etc. have different spectra that we can measure using a spectrometer. As an analogy to visual interpretation, we can say that materials have different “colours” in the infrared region of light. This makes sorting based on actual material type possible just by measuring their spectrum.
A spectroscopy instrument is called spectral if it is capable of aerial imaging. The camera is placed above a conveyor belt and, while the material is passing by, it gives information on the exact material type, position in belt and size. Information is then passed to the sorter for proper action.
When used together with other technologies, spectral cameras make sorting more accurate as they provide true information on material type. The latest generation of hyperspectral cameras can increase the purity of recycled materials to close to 100%. This is important since the possibility to recycle plastic polymer for example generally depends on the material purity. Increasing the purity of recycled material by even a few percents can double its value. Extracting more recyclable material also means that we are disposing less waste to landfill.
Very recent advances in spectral camera technology further to infrared spectrum has made it possible to develop a camera that is also capable of separating black plastics, which has been a huge, unsolved problem hindering recycling efficiency for many years.
Recycling and sorting systems will continue to evolve and become more accurate and easier to implement. At the same time, these systems become completely automated and use different sensors and robotics. One thing is certain: the spectral camera is one key element for improving recycling success.