Materials handling
Meanwhile, BHP Group is looking at the potential of waste from its Australian nickel mining operations to capture and store carbon, with field trials planned for 2022. With an aim of reducing the carbon emissions generated from mining, the dam in Western Australia can store 40,000t of carbon dioxide from the atmosphere each year – enough to offset around 15,000 average-sized combustion engine cars. As for Jensen’s research, she believes that as much as 10% of the cement in concrete can be replaced by mine tailings. So much energy is consumed in cement production that you can transport 1t of material by ship for approximately 20,000km before you exceed CO2
emissions from
Mine tailings could potentially be used to substitute cement in concrete.
Pernille Erland Jensen, associate professor in the department of civil engineering at Technical University Denmark (DTU), this is a process she is all too familiar with. When it comes to the potential of mine tailings and their ability to potentially substitute some of the cement in concrete, it’s literally her field of expertise. And hidden in the depths of Jensen’s research, she hopes, is an environmentally sustainable solution to cement substitution – and one that might aid an escalating supply chain crisis in the industry.
“In terms of goals we’ve set to eliminate coal- firing plants, if we don’t get another product that’s useful to [the industry], then they will have to increase the use of cement, which increases CO2
emissions and the climate impact of mining companies.” 40,000t
The amount of carbon dioxide that waste-storing can capture each year, enough to offset about
15,000 combustion engine cars.
Mining.com 12
Old methods, new direction Jensen is quick to point out that repurposing mine tailings is not a groundbreaking idea. “It’s really not a new thought to utilise waste materials using coal fly ash and other by-products,” she explains, “but now we’re at a turning point because the fly ash is ceasing, and we need to find something else”. The concept of finding value in waste is sweeping the industry at large – more as a necessity than a trend. The Wall Street Journal has even claimed that waste is fast becoming a valuable commodity that could ease the global supply crisis. Waste produced at Rio Tinto’s Kennecott mine in the US, for example, contains critical minerals such as tellurium, which have frequently been disregarded by mining operators the world over in favour of copper.
emissions and the climate impact of concrete production.” This is not something any stakeholders or industry players want to happen. The construction industry at large, including stakeholders, is keen to find a solution to this shortage that does not worsen the impact of global warming, but the mining industry is slower off the mark. One of Jensen’s published reports – ‘Evaluation of mine tailings’ potential as supplementary cementitious materials based on chemical, mineralogical and physical characteristics’ – explains that the benefits of using supplementary cementitious materials (SCMs) could have a remarkably positive impact on the industry’s pollution levels.
cement productions, DTU research reports. The calculations are based on an average for ocean and ‘inland’ transport by sea. Without inland transport by sea, the figure is around 60,000km. Finding a cement replacement that is environmentally and financially viable, however, is the real challenge. “In terms of goals we’ve set to eliminate coal-firing plants, if we don’t get another product that’s useful to [the industry], then they will have to increase the use of cement, which increases CO2
Of these potential benefits, the most significant is the reduction of cement consumption, since the cement manufacturing industry is “contributing massively (5–8%) to the total anthropogenic CO2
emissions”, the report states. It is therefore important to consider the properties future SCMs might have, whether they themselves are hazardous to the environment, and if they can be used in concrete as a sustainable and widely accepted alternative to cement.
Jensen acknowledges that the mining process requires a lot of energy and, as a result, a large quantity of waste and tailings are generated. Therefore, “directing part of the mining waste to the substitution of cement” can help to counteract this. “A lot of energy has already been spent on grinding rock materials down into very fine powders,” she adds, “which will then end up as mining tailings – the most hazardous waste from mining.”
World Mining Frontiers /
www.nsenergybusiness.com
sakoat contributor /
Shutterstock.com
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