Since “Clean Recycling” is an integral part of our “Zero Emission” technology, we at BNL Clean Energy are highly interested in urban mining. The popular science perspective on this phenomenon was covered in a previous article. Here we will focus on where science stands today and what the future might bring
An initial comment must be made on the name of this concept. To scientist, ‘urban mining’ sounds too imprecise and they therefore speak of the ‘mining of the technosphere’ (the sphere affected by human technological activity) or ‘anthropogenic mining’ (where anthropogenic stands for all human impact on nature). Both expressions underline a sharp contrast with traditional mining. Mineral resources in the bedrock first need to be discovered. Those created by humans, on the other hand, are almost always documented somehow. We know where they are located and sometimes even which elements can be found. Additionally, there is a rich resource type which is unique for the technosphere: the big quantities of valuable substances which are in use in society – mobile phones, laser equipment etc – which can be recuperated at a later stage.
To identify which elements can be recovered and whether it is environmentally acceptable to do so, scientists use two main models. With material flow analysis they quantify where different amounts of a particular substance are circulating – from the moment of extraction, via the products where they are being deployed to how they are recycled and thereby enter into a new round in the cycle. To this they add life cycle analyses, which describe how a particular element is mixed with others in different applications in order to establish what measures will later be needed to refine it so that it can be used again. If the latter analysis reveals that we spend more energy and cause more greenhouse gas emissions when recycling substances instead of extracting virgin resources, the latter will typically be the preferred choice.
Aluminum is a good example. To recycle this element you need only 5% of the energy required to extract it from mines. This indicates that recycling is profitable. However, aluminum is very often used in the form of alloys. As long as other elements are added in a small amounts – eg. beverage cans (aluminum +1% magnesium, 1% manganese, 0.4% iron, 0.2% silicon and 0.15% copper) – recycling can be efficient as well as financially viable. Having said that, in casting we find a huge variety of aluminum alloys – the automotive industry alone is estimated to list some 200. In such situations recuperation is difficult and any further use of the materials is severely limited.
Environmental trade-offs are often encountered when life cycle analyses are carried out related to the exploitation of landfills. At first glance, the activities may seem attractive because of an access to raw materials combined with a reduction of landfill gas emissions (mainly methane CH4), which would otherwise be released into the atmosphere and drive the greenhouse effect. (The comparative impact of CH4 on climate change is more than 25 times greater than that of CO2 over a 100-year period.) The reality, however, is more complex. As per today, only metals can be recycled profitably. The rest of the excavated waste must be incinerated and with current technology that results in emissions of carbon dioxide. For this reason scientists suggest that we only extract those dumps where we know that they contain a lot of metal and where the landfill was recently constructed. In such cases the potential amount landfill gas is so high that the measure is justified from an environmental perspective.
Here we can discern one of the directions which the mining of the technosphere might take in the future. As has long been the case in the traditional mining industry, extraction might be focused on commercially viable sites. At the same time, another trend might influence those elements which are not yet buried underground since they are still be in use. More and more products might be designed with a material life cycle analysis in mind. With time, we can expect a standardisation taking place to reduce the number of eg. aluminum alloys since that could sharply increase the recycling rate. Future houses might from the very outset be regarded as storages of raw materials for future use and hence be built with an architecture facilitating demolition accompanied by recycling. As you will understand, urban mining is here to stay although the incentives for it might be lower right now when commodity prices are low.
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Earlier this year we received a comprehensive introduction into the mining of technosphere at a conference with the same name, held at the Technical University of Vienna. During two days, in the dome of the school’s historical main building, we had the opportunity to meet Europe’s leading researchers in the field. The solutions which BNL Clean Energy offers for ‘Zero Emission’ waste treatment and ‘Clean Recycling’ were received with great enthusiasm.
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Find here our earlier, related post: What is Urban Mining?
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Photo by Draco2008 (Creative Commons)