The times we live in are the most innovative, rapidly developing and advanced times humans have ever known. Looking ahead into the future does not give us any reason to doubt that this trend will end anytime soon, which is awesome. However, replacement cycles of consumer electronics are getting shorter and shorter, and with it more and more devices are being thrown away.
In 2016 alone, 44.7 million metric tonnes of e-waste were generated, which is the equivalent of 4500 Eifel towers. This expected to grow to 52.2 million metric tonnes by the end of 2021, with an annual growth rate of 3 to 4%. Of this only 20% is supposed to be collected and recycled, the other 80% is not documented and very likely to be dumped, traded or recycled under inferior conditions.
This huge improperly treated waste stream does not only harm the environment but also the health of animals, including humans, that come in contact with it. There are about 60 different chemical elements present in this e-waste stream that spread via water, air, soil, dust and food. Some of these elements, like lead, mercury and cadmium, are very hazardous, especially for children, and can lead to irreversible cognitive deficits and behavioural and motor skill problems. Besides this, not properly recycling e-waste also depletes our earth of very precious and rare materials like gold and platinum. This may not only lead to shortages, but also requires the continuous mining of new raw materials which is very hazardous and damaging to the environment on itself. The United Nations University estimates the raw materials that can be retrieved from e-waste to be worth around €55 billion.
We believe in a world where these problems are non-existent. That’s why we are working on a solution that allows for the industrial application of elementary retraction: a technology that we leverage for recycling materials, such as e-waste, properly.
We draw our inspiration from the earth itself. Our planet has been performing elementary retraction for as long as it exists. Waste drops to the ocean floor and sinks into the core of the earth, which is how we get our name. It is then heated up and eventually ends up on top again after millions of years trough natural processes like volcanic eruptions. The problem with this is that society progresses at such a pace that the earth can’t keep up anymore. To avoid these problems, we’re going to adapt this process to an industrial scale. Using our technology, we aim to recycle materials like the Earth does
In most cases elementary retraction is fairly easy to apply, since most waste streams contain closely mixed materials. However, in the case of e-waste, the stream contains a highly complex mixture of dozens of elements in a matrix of plastic and silicon. With batteries, which is what we are currently working on, it gets even worse as they contain volatile materials as well. This makes mechanical separation both hazardous and complex, and in the case of chips nearly impossible.
Elementary retraction avoids these issues and aims to recover these materials by heating them to fairly high temperatures in a reactor, exceeding their melting points, up to 1450 °C. This causes plastics to be incinerated and the metals to melt or vaporize (e.g. zinc and cadmium, both commonly found in batteries, have boiling points of 907 °C and 767 °C respectively). By doing this we form three layers.
At these temperatures organic contaminants (including toxic substances like PFOS, of which you can learn about in the video below) fall apart into their constituent elements, which are then oxidized. This process produces various gases like CO, CO2 and NOx. Plastic containing bromine-based fire retardants result in the production of Br2. Therefore, we make use of a gas washing installation. We, for instance, remove CO by using catalytic converters, with the CO2 being cleaned by using an amine-installation.
Through the addition of sand SiO2, a slag layer is formed. This slag layer absorbs contaminants such as silicon and oxides. The viscosity of the slag is maintained through balancing between acidic and basic components – with SiO2 as an acidic and CaO as a basic component for example. This slag viscosity is a crucial factor within our process and is carefully maintained to allow slag to flow freely and to improve exchange speeds between the 3 layers. After cooling down rapidly, the slag remains amorphous resulting in a glassy black substance: obsidian. This can be used for construction projects; in roads and buildings.
The metals, after melting, combine into a third layer below the slag, since they are heavier. Various alloys are then formed, depending on the phase compositions. These are analyzed using thermodynamics software. After melting and separation, the metal layer can be poured off. The different elements can be separated using hydrometallurgical processes, for example by dissolving them, and then applying electrolysis or precipitation to separate specific elements.
To reach these temperatures, the mixture is initially heated up electrically or with burners. Once a certain temperature is reached, the organic compounds (other waste) that we add to the mix will start reacting as well, producing additional heat. The goal of the mixture is then to have the right ratio of exothermic to endothermic components. At the same time the mixture also has to have enough carbon present to avoid oxidizing the metals at any particular temperature. We like to call this mixture the “smart mix”. This smart mix reduces the amount of consumed energy significantly, while also presenting the possibility to process other waste streams together with e-waste, making it not only a very sustainable solution but also financially interesting.
As the specific composition of the different e-waste streams can vary, we are working on a procedure for determining the right amount of slag, the optimal temperature, viscosity and so on. This includes mass balances, energy balances, separation rates, thermodynamic models on the alloying, slag-forming and oxidation behaviors and viscosity predictions
 Baldé, C.P., Forti V., Gray, V., Kuehr, R., Stegmann,P. : The Global E-waste Monitor – 2017, United Nations University (UNU), International Telecommunication Union (ITU) & International Solid Waste Association (ISWA), Bonn/Geneva/Vienna.
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