REMEDIATION
ENVIRONMENTAL ISSUES
SOIL REMEDIATION SEES GREEN MINING INNOVATION PHIL KNEEBONE, MANAGING DIRECTOR, SHIFT SOIL REMEDIATION LLP
Long before the current resource boom fuelled the extractive industries, the mining sector was transformed by high-tech resources distributed over exploration, extraction and processing. This transformation continues and with the introduction of green mining technologies, now encompasses the environmental aspect too. There is no inconsistency, as some people suggest, to the term ‘green mining’ and this is not some short joke like ‘military intelligence’ or ‘virtual reality’. There is something that is surprisingly true within the kernel of clichéd oxymoronic statements but any supposed paradox in green mining is not fair considering the practicality of environmentalism meeting the extractive industries. Our love-hate relationship with ‘things’ and their real price quite rationally leads to a bitter sweet understanding of the cost of sourcing the resources against the benefit of consumption, but the idea of sustainable mining is anything but mutually exclusive. The basic discontinuity comes from the idea that modern mining projects leave behind disrupted communities, damaged landscapes, and polluted water. Green mining describes methods by which the waste produced by mining is transformed into environmentally friendly resources for other uses, leaving behind healthy ecosystems with clean water and rehabilitated landscapes. The four pillars of green mining are: footprint reduction, innovation in waste management, rehabilitation of
mine site and ecosystem risk management. The rise of green mining does not reflect a cultural shift in the industry, beyond what is happening across all society, but is the result of a number of progressive regulations and taxes; such as the Quarries Tip Act, the Waste Mining Directive (WMD), and the Landfill Levy; all of which deal with the issue of waste and define how the mining industry can be regulated and methods improved. Caterpillar, the construction and mining equipment manufacturer, has addressed some of these issues and developed an innovative engine technology called ACERT™ which delivers a 5 per cent improvement in fuel efficiency, up to 90 per cent reduction in particulate matter and 50 per cent reduction in oxides of nitrogen.
Similarly, the mining giant Vale plans to cut their carbon emissions by 20 per cent using a fuel of 20 per cent biodiesel and 80 per cent diesel in all of their machines. They expect to save $US 150 million per year in the process. No matter how efficient or clean any mining technology used, there is usually some form of remediation needed. A common example is the spillage of fuels during normal operations. On a large mine, the amount of polluted soil arising just from this can run into thousands of tonnes annually. Many methods have been used for remediation but there are five prominent approaches to treating hydrocarbon impacted soil. These are: ●
Bio-remediation (use of bacteria)
PHIL KNEEBONE ●
Encapsulation (use of concrete or lime to immobilise contaminate)
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Soil washing
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Phytoremediation (use of plants to bio accumulate the contaminant out of the ground), and
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Thermal destruction/desorption (use of heat).
Remediation methods and drivers through time
QUARRIES & MINES 2012
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ENVIRONMENTAL ISSUES
Acid mine drainage is one of the worst environmental problems faced by the mining industry The main by-products of mining are tailings, the waste product of ore-processing facilities, which contain a high concentration of heavy metals. These tailings can be susceptible to erosion or removal by wind and water, adding further to problems such as water contamination. Electrokinetic remediation has been shown to be successful in such cases, as it relies on the application of a low-intensity direct current through the soil between ceramic electrodes. This mobilises charged metal particles in water causing them to move toward the electrodes where they can be collected and treated. Although heavy metals and petrochemicals prove more difficult to
REMEDIATION
remediate, acid mine drainage (AMD) is the worst environmental problem faced by the mining industry. This is generally treated with alkaline reagents such as limestone, lime, soda ash etc. This in itself is relatively effective but can be combined with barrier technology to produce even better results. Permeable reactive barriers enable treatment of contaminated groundwater by directing flow through reactive materials placed in trenches. So far, a combination of compost, limestone and recycled steel slag dusts has been found to be the most effective but other treatments/combinations are also being investigated to determine their effectiveness. An example of prevention in the case of AMD is the Haber Gold process (HGP is exclusively owned by US-based Omai Gold Mines). The process operates by extracting the gold from its ores by dissolving the gold into water using non-toxic chemicals where it can then be recovered. The key factor in the success of this solution is that it does not lead to
the release of heavy metals such as mercury, cadmium and lead. While there is ever more innovative remediation technologies to address the toxic or harmful pollutants produced as a result of the mining process, the problem of inert ‘waste’ must also be addressed; while not directly affecting the environment by toxic contamination it will contribute to visual pollution and leave the site in an inactive state once closed. Another use of this recycled aggregate is a substance called Plastisoil, created by Naji Khoury. It is a combination of polyethylene terephthalate, which is pulverised and mixed with soil, blended with a coarse aggregate and then heated to create a hard yet non-watertight substance similar to porous asphalt. The unique properties of Plastisoil allow rainwater to flow completely through and not run over the surface of the ground, collecting contaminates at it goes which then flow into our rivers.
Offering cost-effective solutions at competitive prices
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QUARRIES & MINES 2012
There are many examples around the world of effective mine and quarry regeneration – possibly the most famous in the UK is the Eden Project – but there are numerous other uses ranging from heritage and tourism attractions, wildlife habitats, educational, sport and leisure facilities, concert venues and dozens of industrial uses. The green mining revolution will continue and increase in pace as new technologies are developed and innovations sought and drawn from the medical, space and military fields. Mining, just like other business, has always been conducted with sustainability in mind. It is just that we have now changed our view of sustainability.
For further information, visit: www.shiftsoil.co.uk
