- Email: [email protected]
The mine of the future – Even more sustainable
Minerals Engineering xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Minerals Engineering journal homepage: www.elsevier.com/locate/mineng
The mine of the future – Even more sustainable R.J. Batterham University of Melbourne, Kernot Professor of Engineering, Australia
a r t i c l e
i n f o
Article history: Received 8 August 2016 Revised 31 October 2016 Accepted 1 November 2016 Available online xxxx Keywords: Mining Sustainability
a b s t r a c t Sustainability is something that is ever important but not necessarily easy to progress. It can get rather complex quite quickly and with diverse and critical stakeholders, we have to be very systematic. This paper is a discussion on sustainability over the years with a focus on the changes seen in the mining industry. Despite somewhat heroic efforts by the industry to take a coordinated approach to sustainability, it is clear that many see mining as broken. The paper discusses some of the technical advances both near term and longer that will ensure that mining is seen as sustainable and that companies are seen as integrated development partners. The mine of the future will be very deep, will have a negligible footprint, much lower energy requirements and will only bring to the surface the primary products required by an increasingly circular economy. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction: sustainability as a journey Sustainability is ever important as a self-evident common good. Few would argue against a principle that aims to ensure stable or ever improving living standards, or more generically, that future generations should not have their choices limited. The topic is not new. We can turn to (Malthus, 1872) in his essay on the evils of population growth as sowing the seeds of the sustainability debate. His essay is still seen as a topic for debate in modern economics (Brander, 2007). It is hard to argue against the principle that unmitigated population growth would strain resources to the point of limiting the growth, let alone living standards. That said, the green revolution in agriculture has permitted a global population (most likely) unimaginable to Malthus. Perhaps the most focusing debate in modern times was the publication of The Limits to Growth (Meadows et al., 1972). The book focuses repeatedly on sustainability and particularly the need to alter ‘‘growth trends and to establish a condition of ecological and economic stability that is sustainable far into the future.” The Club of Rome used the analysis to emphasise that we live in a finite system. Their long term predictions of running out of oil (1992), natural gas (1994) and finally coal (2083) have long since been shown to be in error. This has led to much criticism of the work as ignoring the nature of technology or the fact that resources are still in abundance, albeit with lower grades and higher energy requirements. Recent work however (Turner, 2014) suggests that the base case of the Limits to Growth aligns well with current data with first signs of a general collapse appearing around 2015. Turner
suggests peak oil and energy resource constraints as key factors. One might argue however that the current selling price for oil (excluding exploration and development costs) is still a factor of 3 above the marginal cost of production. The base scenario in limits to growth is still well short of reality. Close inspection however indicates that Meadows et al. (1972, page 130) were in fact well aware that ‘‘There are no substantial limits in sight either in raw materials or in energy that alterations in the price structure, product substitution, anticipated gains in technology and pollution control cannot be expected to solve”. The real criticism of the work is that it underestimated the impact of technology in terms of improving pollution levels and bringing down costs. One notes that for commodities in general and for mineral commodities in particular, over the long term price in real terms keeps falling (Fig. 1). This trend is hardly driven by discovery of ever higher grades but more by the relentless March of technology. One might even define a commodity as something whose price falls in real terms indefinitely. Should a finite limit ever occur, substitution would then apply. It is easy to adopt a non-critical view that sustainability issues concerning finite resources will be solved by technology but equally, the relentless advances in technology are often underestimated. As pointed out in the narrative, (Williamson et al., 2015) it is technology that is central to human existence. A tangential but informative aspect is to note, that technology is a great leveler. As production increases, costs come down over orders of magnitude (Fig. 2).
http://dx.doi.org/10.1016/j.mineng.2016.11.001 0892-6875/Ó 2016 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Batterham, R.J. The mine of the future – Even more sustainable. Miner. Eng. (2016), http://dx.doi.org/10.1016/j. mineng.2016.11.001
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R.J. Batterham / Minerals Engineering xxx (2016) xxx–xxx
Fig. 1. Commodities have been a terrible investment in real terms, over the long run. BCA Research. Adjusted by U.S. GDP deflator; shown as a natural logarithm.
Fig. 2. Unit costs and global production are strongly related (Batterham, 2015).
2. The sustainability journey for mining Probably the most significant event after the Club of Rome activity was the publication of the Brundtland (2009) report. We are all well familiar with its focus on sustainability and its simple definition of sustainable development as ‘‘meeting the needs of the present without compromising the ability of future generations to meet their own needs”. The simplicity of the definition is beguiling but as to measurement and the ability to compare and choose between alternatives, no consensus has ever been reached (Batterham, 2006). For the mining industry at a corporate level there have always been requirements on stewardship (award of licences and allocation of royalties and taxes), environmental performance requirements (often ever increasing) and the need to satisfy shareholder expectations or risk going out of business. While lofty ideals such as The Natural Step (Robert, 1989) seem to offer a quantitative approach they can be difficult to apply in the context of mining. More specifically, the Natural Step requires mining not to produce materials any faster than they are returned to the Earth’s crust. Even just from an energy perspective, this is not simple (Gutowski et al., 2013). As well, an urbanizing and growing population requires at least for some years more materials. More realistically, mining companies tread a progressive line somewhere between ‘‘staying out of jail” in terms of regulation and the wider public licence to operate and the pursuit of a myriad of goals (waste minimization, product purity, utilization of bi-products, social investment, etc.) that in summation would bankrupt a company.
For many in the industry, the journey in more recent times has centred on the so called triple bottom line, attributed to Elkington (1997) but in the literature much earlier (Spreckley, 1981). It provides headings for companies to report, albeit still descriptive rather than allowing quantitative comparisons in an absolute sense. At least the headings are readily comprehensible, eg People, Planet, Profits or Social, Environment and Economic. To these banners and in response to public pressure, a fourth pillar is often added, viz Governance (Rio Tinto, 2014). To some extent, the public licence to operate has always been a priority. The revolution that closed Bougainville Copper operations in 1989 (Anon, 2013) is but one reminder that withdrawal of the public licence to operate can take quite extreme forms. Equally dramatic in terms of halting progress can be Government moratoriums, e.g. that by the Victorian Government on fracking (ABC, 2012) while targeting non-conventional gas production in effect bans the mine of the future as outlined in this paper. Understanding the stakeholders would seem to be the key to maintaining the public licence to operate. As Reggio and Lane (2012) show, this is far from simple (Fig. 3) and, even with attention to detail, there is no guarantee of success, merely a better chance of procuring and maintaining the licence to operate. Some would argue that stakeholder engagement is nothing new and is a continuous part of an effective sustainability strategy. This is reasonable but tends to hide the fact that significant changes can take many years to negotiate, e.g. the 7 years required for Rio Tinto in the Pilbara to negotiate a new stakeholder agreement even after 20 years of effective collaboration with stakeholders (Rio Tinto,
Please cite this article in press as: Batterham, R.J. The mine of the future – Even more sustainable. Miner. Eng. (2016), http://dx.doi.org/10.1016/j. mineng.2016.11.001
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Fig. 3. The complexity of understanding stakeholders (from Reggio and Lane (2012)).
2013). What is very clear is that stakeholder engagement is a key part and an ongoing part of all mining (Fraser and Scoble 2016). 3. Global initiatives in sustainable mining The performance of individual mines in terms of sustainability is very visible, and that world-wide. As a consequence, the industry has banded together at national and international level to share, define and openly show that mining is sustainable. Sustainability of a wasting resource must of course include a position that further exploration and development is a key part of sustainability, at least until the world demand for primary materials subsides and recycling and reuse are the norm; the energy requirements of this circular economy presumably supplied sustainably. Most see such a position as at least 30–50 years away. Gutowski et al. (2013) still see demand for materials in 2050 as being more than 2 times that of 2015. So, in the meantime, the industry as well as its component companies, have a clear task: to make the mine of the future even more sustainable. Pressure to form more effective industry alliances resulted in the formation of the Global Mining Initiative for Mining, minerals and sustainable development, led by Wilson (2000). ‘‘The declared aim of the GMI is to ensure that an industry that is essential to the well- being of a changing world is responsive to global needs and challenges”. It was clear and remains clear that the industry must find new ways to respond to public concerns. Following the broad support in the industry for the GMI, the International Council on Mining and Metals (ICMM, 2016) was established in 2001 to act as a catalyst for (general) performance improvement in the mining and metals industry. It continues and encourages companies to be more willing to engage constructively with critics and to listen more carefully to what they have to say. There are numerous other national (e.g. MEND (1989) in Canada) or focused efforts such INAP (2002) covering acid mine drainage. As well, most of the professional bodies catering to mining and metals production have sustainability charters and active discussion and dissemination of development amongst their members. Despite the plethora of activity, there is a growing realisation that there are strong drivers for change. In 2012 the Kellogg
Innovation Network convened a diverse group of people to recognise that mining as we know it is dead and that a new approach is needed. The clear outcome after a year and a half of deliberation is that mining companies must become integrated development partners with all stake-holders: a most worthwhile message but not particularly new. The World Economic Forum in its annual meeting at Davos in 2014 similarly tackled the issue of mining sustainably. The briefing paper noted that ‘‘global markets remain weak following the global financial crisis, commodity prices have fallen, and shareholders are pushing for leaner operations and greater returns on investment. At the same time, the stakeholder landscape for mining and metals companies is becoming increasingly diverse, with growing expectations for companies to operate in a responsible and sustainable manner”. This is again not really a new message yet it still remains urgent enough to feature at Davos, even after the formation of the Global Mining Initiative in 2000. Rising concerns about artisanal mining, an intensified rate of technological change, abrupt generational change, a growing concern for the environment, increased ‘‘democratisation” and a higher demand for fairness are all likely to contribute to a redefining of values and a rethinking of the present multi-stakeholder model. There are many other examples of the ‘‘Mining as we know it is dead” theme, e.g. Hitch et al. (2015), some quite enlightening in terms of the solutions proposed. As already pointed out, mining companies must and do operate at some point on the scale between ‘‘staying out of jail” and pursuit of ‘‘perfection in sustainable mining”. What seems clear at a generic level is that leadership from management will continue to be critical but so will new technology. It is the author’s opinion that adoption of the technological initiatives outlined in the rest of this paper could deliver progress towards a much more sustainable and more economic mine of the future. 4. The mine of the future – deep underground There have been many visionary opinions of the mine of the future, not least from this author (2003). One suggestion is for a mine that is essentially not visible on the surface and only brings to the surface the primary material of value. If the surface footprint
Please cite this article in press as: Batterham, R.J. The mine of the future – Even more sustainable. Miner. Eng. (2016), http://dx.doi.org/10.1016/j. mineng.2016.11.001
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R.J. Batterham / Minerals Engineering xxx (2016) xxx–xxx
is to be negligible, then subsidence or interference with lakes is not allowable. Equally, interference with aquifers is also not permissible. The vision therefore suggests deep mineralizations that are exploited essentially by in-place leaching. An outcome of being more than 1 km deep and with no interference with the surface is that a mine is equally acceptable in an urban setting as in a remote area. This is quite some advantage in terms of finding the skills to develop and operate such a mine. It would be a very high-tech affair. To put such a step change into perspective, one might look at the industry over the last 200 years and note that there have been at least 3 transformative changes: Flotation, initially to recover zinc from waste material in 1902, albeit with some parallel developments a little earlier. Open pit mining (using massive steam shovels in a copper mine at Bingham Canyon in 1906). Solvent extraction – electrowinning, initially for uranium extraction in world war 2 and then for copper in the 1960s). Against this background, another transformative change is well due. Interestingly, there is significant progress in the technologies needed for deep underground in-place mining. One must explore, then access then stimulate the mineralization. On the question of exploration, many of the techniques developed for the oil and gas industry are relevant to mineral exploration and exploitation. The geophysical side has been noted by Sinclair and Thomson (2015) and was extensively reviewed at the In Situ Recovery conference in Adelaide organized by CSIRO and the University of Adelaide (Robinson and Grano, 2015); the papers on targeting and characterizing natural fractures being particularly relevant. If large-scale access is required to these deep mineralizations, then the automation of more conventional approaches will be a key to economic implementation. Automation of underground operations has been ongoing for many years, with LKAB one of the pioneers in the field in the late 1980s (Nilsson et al., 2001). Automation of existing processes in deep mines to 1.5 km is seen as fully practicable by 2030 (Bäckblom et al., 2010) and indeed the essential step towards subsequent winning of base metals beyond 2030 by in-situ production with zero waste and no human intervention. The Scandinavian countries are not the only groups to recognize the importance of deep underground mining to the future of mining. The Canadian Group on Ultra Deep Mining Network (UDMN, 2015) has garnered $46 m (including $16 m from the Canadian Government) to tackle developments. We can conceptually see the mine of the future from two evolutionary paths, albeit with convergence. One is from conventional underground mining where broken material is leached in-place and the other is from bores drilled to a mineralization which is fracked and then leached. To some extent the first is an evolution of existing mining methods and there are several examples of where broken material remaining in stopes has been leached (Sinclair and Thompson, 2015) but no examples yet of where this was the primary method of production. The second method is an evolution from the solution mining of uranium in sedimentary locations and applying the exploration, fracking and development methods of the oil and gas industry to hard rock mineralizations. Time will tell the most fruitful paths. Copper is an interesting case study. Since the discovery of Resolution in Arizona (Briggs, 2015) in 1995, this massive but deep porphyry system has shown the world what many have long suspected, that there is much potential for future mining of copper to be deep underground. At 2 km deep and a possible temperature of 80 °C, it is an obvious target for the mine of the future. Delineating such mineralizations will increasingly benefit from
advanced geophysical techniques, especially those developed for the oil and gas industries (Fraser, 2015). As Sinclair and Thomson (2015) have pointed out, there are examples of copper leaching underground as secondary operations. The presence of chalcopyrite per se is not seen as a limitation. It is a challenge in that both Eh and pH must be controlled to prevent passivation. Equally, the gangue material must be appropriate. High acid consumption or gypsum precipitation are known challenges although options are available. What is fundamentally interesting and hopeful for deep leaching is that as depths increase, so does pressure and hence oxygen solubility, likely giving much higher leaching rates (McDonald, 2015). As an example, oxygen solubility in water at surface is around 8 ppm but is 3570 ppm at 1 km. As McDonald has pointed out, while solubility decrease with temperature, above 300 K, solubility then increases again. Some of this ground is also covered by Vargas (2015) who goes on to point out that chemical pre-treatment can be used to enhance permeability. Vargas and co-workers have developed an experimental methodology for quantifying the implementation and economic considerations of in-situ mining (Bahamondez et al., 2016). 5. Permeability enhancement There have been many visionary opinions of the mine of the future, not least from this author (2003). One suggestion is for a mine that is essentially not visible on the surface and only brings to the surface the primary material of value. If the surface footprint is to be negligible, then subsidence or interference with lakes is not allowable. Equally, interference with aquifers is also not permissible. The vision therefore suggests deep mineralizations that are exploited essentially by in-place leaching. As Grano (2014) has indicated, there are real challenges in enhancing permeability to allow in-situ recovery: Most rock matrix may have ultralow permeability without natural fractures Need to target natural fractures (horizontal bore hole direction) Need hydraulic fractures to intersect with natural fractures Fractures extend in direction of maximum principle stress Natural fractures may be co-located with mineralization? Need to maintain fractures under leach conditions for months/ years Acid resistant proppant but stress an issue on fracture-proppant conductivity It is more likely that initial commercial operations for in-situ mining will be on material that is first block caved and then has the permeability further enhanced. In this respect there are some novel developments in drilling and blasting technology. Blasting has developed in recent years not just in terms of the velocity of detonation and the strength of the blast, but also with the next generation of electronic initiation that is wireless and can include delays up to 30 s. These developments have passed the alpha stage of testing and are now at the beta test stage with certain customers of Boyce (2015) initially targeting niche underground applications such as stranded ore and sublevel cave rings. As Boyce points out, wireless detonation is a game changer in that automated drilling and charging are a reality. Electronic ignition means that from a sub level, holes could be drilled for several levels and then with a single sequence, the rock initially cracked (or preconditioned) and then the broken rock further comminuted by gas pressure and reflection effects. As Boyce (2015) suggests, ‘‘such a hybrid method could be developed to create large underground reactors for leaching of minerals” (see Fig. 4).
Please cite this article in press as: Batterham, R.J. The mine of the future – Even more sustainable. Miner. Eng. (2016), http://dx.doi.org/10.1016/j. mineng.2016.11.001
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are many further enhancements possible on the road to in-place leaching and recovery. Without being prescriptive, developments may include: Much cheaper, automated small hole directional drilling s for permeability control s hydrothermal spallation and high voltage pulse breakage for permeability Real time tracking of lixiviate Chemical tracers and nanomachine measurements Much more tailored and exotic organisms and peptides (Vargas, 2015), e.g. s Metal accumulating bacteria (e.g. Delftia Acidovorans) s Gangue leaching (e.g. Ferroplasma acidamanus). 8. In summary
Fig. 4. High lift drawbell plus post conditioning concept. (Boyce, 2015).
As a step towards demonstrating ‘‘high fidelity” control of explosives, experiments are underway in a European copper mine with a high grade seam. The blasted material in the ‘‘reactor” will be leached in-situ as a bioleach.
One can argue that despite many years of attention to sustainability, mining as we know it is in need of significant change. The mine of the future is technically feasible today, albeit at a Technology Readiness level less than that required for large commercial projects. First major steps are likely to be in large, deep ore bodies such as porphyry copper mineralizations. Caving to produce a reactor of broken material and then in-place leaching with barriers in place is all seen as relatively close, years and not 10s of years.
6. Barriers are essential At a fundamental level, in-place leaching requires permeability but ideally the reactive zone does not want to be connected to any groundwater flows. This will be the case from time to time, especially in deeper mineralizations. In most cases however it is necessary to pump out more fluid for production than is added as injected leachate. This is not desirable as the excess must be bled off, treated and disposed of – hardly compatible with a ‘‘zero footprint mine of the future”. As well, one must cope with major long range fractures which can provide paths for short circuiting. Geostatic pressures must also be considered in that overpressuring can inadvertently result in the extension or opening of existing long range fractures. A more appropriate approach is to consider the use of barriers. In the oil and gas industry there is wide spread use of gel barriers to control the flow of sweep fluids, to prevent bypassing and to control production. The lack of application of barriers to date in in-place leaching is more a matter of experience for the industry rather than lack of suitable barriers. The silicate barriers used elsewhere have properties ideal for inplace leaching. It is well known that at reasonable silicate loadings, the gel time for a 3:2 ration sodium silicate to sulphuric acid can vary from under a minute at pH 5 to several hours at pH 2 (PQ Europe, 2016). This means that a solution can be prepared and then pumped into place with a viscosity that of water, the pumping ceased and the gel then forms. This is cheap and effective. In addition, fine particulates can be added that can react with any acid lixiviant that overpressures the gel barrier through inadvertent operations. Such particles can react to expand the gel making it ‘‘self-healing”. Hollitt and Batterham (2002) tested such a barrier to block off a paleochannel which had previously been sheet piled as part of protection for a dam wall built over the channel. The piling had corroded allowing water to start washing away the dam wall. The barrier was low cost, almost trivial to inject and was totally successful. 7. And even further into the future While advanced blasting and barrier technology will most likely first be applied in block caves, as more experience is gained there
Acknowledgments The author acknowledges the initiatives of the University of Adelaide and the CSIRO in forming a working group to help focus efforts on in-situ recovery technologies for metals. The meeting held by the group in Adelaide in December 2015 provided much of the recent material referred to in this paper, including the recent developments at Orica outlined by Stephen Boyce. The papers in the References are accessible through Dr Dave Robinson of CSIRO [email protected]. The contribution of Peter Seligman from Melbourne University to the data in Fig. 2 is gratefully acknowledged.
References ABC News, 2012. Government imposes fracking moratorium (accessed 01.03.16). Anon Mining Legacies: Mineral Policy Institute, 2013. /
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Europe, P.Q., 2016. Sodium and potassium silicates (accessed 01.03.16). Fraser, J., Scoble, N.B., 2016. Social risk as an agent of change. AusIMM Bullet. (February), 24–27 Fraser, S., 2015. Geophysical characterisation to support in-situ recovery. Challenges and Opportunities in Creating Access to Values for In-Situ Recovery of Sub-Surface Resources Symposium, Uni of Adelaide, 9 Dec 2015. Grano, S., 2014. Sensing sub-surface fluid and fracture pathways. Invisible Mining Symposium. CSIRO and Mineral Resources Flagship, Perth. Gutowski, T.G., Sahni, S., Allwood, J.M., Ashby, M.F., Worrell, E., 2013. The energy required to produce materials: constraints on energy-intensity improvements, parameters of demand. Philos. Trans. R. Soc. Lond. A: Math. Phys. Eng. Sci. 371 (1986), 20120003 (accessed 01.03.16). Hitch, M., Geo, P., Dunbar, W.S., 2015. Paths of Innovation in the Mining Industry. Norman B Keevil School of Mining Engineering. Hollitt, M., Batterham, R.J., 2002. Lake Lonsdale demonstration of gel barriers to restrict water flow in a paleochannel. Rio Tinto private communication. International Council on Mining and Metals, 2016. (accessed 01.03.16). International Network for Acid Prevention, 2002. (accessed 01.03.16). Kellogg Innovation Network, 2012. Mining is broken (accessed 01.03.16). Malthus, T.R., 1872. An Essay on the Principle of Population: Or, A View of Its Past and Present Effects on Human Happiness; With an Inquiry Into Our Prospects Respecting the Future Removal or Mitigation of the Evils Which It Occasions. Reeves and Turner, London. McDonald, R., 2015. Sub-surface solution chemistry and its impact on in-situ recovery. Challenges and Opportunities in Creating Access to Values for In-Situ Recovery of Sub-Surface Resources Symposium, Uni of Adelaide, 9 Dec 2015. Meadows, D.H., Meadows, D.L., Randers, J., Behrens III, W.W., 1972. The Limits to Growth: a Report for the Club of Rome’s Project on the Predicament of Mankind Universe Books. New York City. Mine Environment Neutral Drainage, 1989.
Case Studies. Society of Mining, Metallurgy and Exploration, pp. 681–690 (Chapter 75). Reggio, R., Lane, A. 2012. Monitor Deloitte: Mining in Africa: How inclusive solutions can mitigate risk. p12. (accessed 01.03.16). Rio Tinto, 2013. Rio Tinto celebrates new comprehensive land use agreement with Traditional Owners in the Pilbara (accessed 01.03.16). Rio Tinto, 2014. Sustainable development report. (accessed 01.03.16). Robinson, D., Grano, S. (Eds.), 2015. Challenges and Opportunities in Creating Access to Values for In-Situ Recovery of Sub-Surface Resources Symposium, Uni of Adelaide, 9 Dec 2015. Sinclair, L., Thompson, J., 2015. In situ leaching of copper: challenges and future prospects. Hydrometallurgy 157, 306–324. Spreckley, F., 1981. Social Audit: A Management Tool for Co-Operative Working. Beechwood College, Leeds, p. 44. Turner, G., 2014. Is global collapse imminent? An updated comparison of The Limits to Growth with historical data. Melbourne Sustainable Society Institute, Research Paper 4, pp. 22. Ultra Deep Mining Network, 2015. The business of mining deep: below 2.5 km. (accessed 01.03.16). Wilson, R., 2000. Global Mining Initiative: Mining, minerals and sustainable development. Report on the Governors meeting for the Mining and Metals Industry. (accessed 01.03.16). World Economic Forum, 2014. Scoping Paper: Mining and Metals in a Sustainable World, Geneva. (accessed 01.03.16).
Please cite this article in press as: Batterham, R.J. The mine of the future – Even more sustainable. Miner. Eng. (2016), http://dx.doi.org/10.1016/j. mineng.2016.11.001
Contents lists available at ScienceDirect
Minerals Engineering journal homepage: www.elsevier.com/locate/mineng
The mine of the future – Even more sustainable R.J. Batterham University of Melbourne, Kernot Professor of Engineering, Australia
a r t i c l e
i n f o
Article history: Received 8 August 2016 Revised 31 October 2016 Accepted 1 November 2016 Available online xxxx Keywords: Mining Sustainability
a b s t r a c t Sustainability is something that is ever important but not necessarily easy to progress. It can get rather complex quite quickly and with diverse and critical stakeholders, we have to be very systematic. This paper is a discussion on sustainability over the years with a focus on the changes seen in the mining industry. Despite somewhat heroic efforts by the industry to take a coordinated approach to sustainability, it is clear that many see mining as broken. The paper discusses some of the technical advances both near term and longer that will ensure that mining is seen as sustainable and that companies are seen as integrated development partners. The mine of the future will be very deep, will have a negligible footprint, much lower energy requirements and will only bring to the surface the primary products required by an increasingly circular economy. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction: sustainability as a journey Sustainability is ever important as a self-evident common good. Few would argue against a principle that aims to ensure stable or ever improving living standards, or more generically, that future generations should not have their choices limited. The topic is not new. We can turn to (Malthus, 1872) in his essay on the evils of population growth as sowing the seeds of the sustainability debate. His essay is still seen as a topic for debate in modern economics (Brander, 2007). It is hard to argue against the principle that unmitigated population growth would strain resources to the point of limiting the growth, let alone living standards. That said, the green revolution in agriculture has permitted a global population (most likely) unimaginable to Malthus. Perhaps the most focusing debate in modern times was the publication of The Limits to Growth (Meadows et al., 1972). The book focuses repeatedly on sustainability and particularly the need to alter ‘‘growth trends and to establish a condition of ecological and economic stability that is sustainable far into the future.” The Club of Rome used the analysis to emphasise that we live in a finite system. Their long term predictions of running out of oil (1992), natural gas (1994) and finally coal (2083) have long since been shown to be in error. This has led to much criticism of the work as ignoring the nature of technology or the fact that resources are still in abundance, albeit with lower grades and higher energy requirements. Recent work however (Turner, 2014) suggests that the base case of the Limits to Growth aligns well with current data with first signs of a general collapse appearing around 2015. Turner
suggests peak oil and energy resource constraints as key factors. One might argue however that the current selling price for oil (excluding exploration and development costs) is still a factor of 3 above the marginal cost of production. The base scenario in limits to growth is still well short of reality. Close inspection however indicates that Meadows et al. (1972, page 130) were in fact well aware that ‘‘There are no substantial limits in sight either in raw materials or in energy that alterations in the price structure, product substitution, anticipated gains in technology and pollution control cannot be expected to solve”. The real criticism of the work is that it underestimated the impact of technology in terms of improving pollution levels and bringing down costs. One notes that for commodities in general and for mineral commodities in particular, over the long term price in real terms keeps falling (Fig. 1). This trend is hardly driven by discovery of ever higher grades but more by the relentless March of technology. One might even define a commodity as something whose price falls in real terms indefinitely. Should a finite limit ever occur, substitution would then apply. It is easy to adopt a non-critical view that sustainability issues concerning finite resources will be solved by technology but equally, the relentless advances in technology are often underestimated. As pointed out in the narrative, (Williamson et al., 2015) it is technology that is central to human existence. A tangential but informative aspect is to note, that technology is a great leveler. As production increases, costs come down over orders of magnitude (Fig. 2).
http://dx.doi.org/10.1016/j.mineng.2016.11.001 0892-6875/Ó 2016 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Batterham, R.J. The mine of the future – Even more sustainable. Miner. Eng. (2016), http://dx.doi.org/10.1016/j. mineng.2016.11.001
2
R.J. Batterham / Minerals Engineering xxx (2016) xxx–xxx
Fig. 1. Commodities have been a terrible investment in real terms, over the long run. BCA Research. Adjusted by U.S. GDP deflator; shown as a natural logarithm.
Fig. 2. Unit costs and global production are strongly related (Batterham, 2015).
2. The sustainability journey for mining Probably the most significant event after the Club of Rome activity was the publication of the Brundtland (2009) report. We are all well familiar with its focus on sustainability and its simple definition of sustainable development as ‘‘meeting the needs of the present without compromising the ability of future generations to meet their own needs”. The simplicity of the definition is beguiling but as to measurement and the ability to compare and choose between alternatives, no consensus has ever been reached (Batterham, 2006). For the mining industry at a corporate level there have always been requirements on stewardship (award of licences and allocation of royalties and taxes), environmental performance requirements (often ever increasing) and the need to satisfy shareholder expectations or risk going out of business. While lofty ideals such as The Natural Step (Robert, 1989) seem to offer a quantitative approach they can be difficult to apply in the context of mining. More specifically, the Natural Step requires mining not to produce materials any faster than they are returned to the Earth’s crust. Even just from an energy perspective, this is not simple (Gutowski et al., 2013). As well, an urbanizing and growing population requires at least for some years more materials. More realistically, mining companies tread a progressive line somewhere between ‘‘staying out of jail” in terms of regulation and the wider public licence to operate and the pursuit of a myriad of goals (waste minimization, product purity, utilization of bi-products, social investment, etc.) that in summation would bankrupt a company.
For many in the industry, the journey in more recent times has centred on the so called triple bottom line, attributed to Elkington (1997) but in the literature much earlier (Spreckley, 1981). It provides headings for companies to report, albeit still descriptive rather than allowing quantitative comparisons in an absolute sense. At least the headings are readily comprehensible, eg People, Planet, Profits or Social, Environment and Economic. To these banners and in response to public pressure, a fourth pillar is often added, viz Governance (Rio Tinto, 2014). To some extent, the public licence to operate has always been a priority. The revolution that closed Bougainville Copper operations in 1989 (Anon, 2013) is but one reminder that withdrawal of the public licence to operate can take quite extreme forms. Equally dramatic in terms of halting progress can be Government moratoriums, e.g. that by the Victorian Government on fracking (ABC, 2012) while targeting non-conventional gas production in effect bans the mine of the future as outlined in this paper. Understanding the stakeholders would seem to be the key to maintaining the public licence to operate. As Reggio and Lane (2012) show, this is far from simple (Fig. 3) and, even with attention to detail, there is no guarantee of success, merely a better chance of procuring and maintaining the licence to operate. Some would argue that stakeholder engagement is nothing new and is a continuous part of an effective sustainability strategy. This is reasonable but tends to hide the fact that significant changes can take many years to negotiate, e.g. the 7 years required for Rio Tinto in the Pilbara to negotiate a new stakeholder agreement even after 20 years of effective collaboration with stakeholders (Rio Tinto,
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Fig. 3. The complexity of understanding stakeholders (from Reggio and Lane (2012)).
2013). What is very clear is that stakeholder engagement is a key part and an ongoing part of all mining (Fraser and Scoble 2016). 3. Global initiatives in sustainable mining The performance of individual mines in terms of sustainability is very visible, and that world-wide. As a consequence, the industry has banded together at national and international level to share, define and openly show that mining is sustainable. Sustainability of a wasting resource must of course include a position that further exploration and development is a key part of sustainability, at least until the world demand for primary materials subsides and recycling and reuse are the norm; the energy requirements of this circular economy presumably supplied sustainably. Most see such a position as at least 30–50 years away. Gutowski et al. (2013) still see demand for materials in 2050 as being more than 2 times that of 2015. So, in the meantime, the industry as well as its component companies, have a clear task: to make the mine of the future even more sustainable. Pressure to form more effective industry alliances resulted in the formation of the Global Mining Initiative for Mining, minerals and sustainable development, led by Wilson (2000). ‘‘The declared aim of the GMI is to ensure that an industry that is essential to the well- being of a changing world is responsive to global needs and challenges”. It was clear and remains clear that the industry must find new ways to respond to public concerns. Following the broad support in the industry for the GMI, the International Council on Mining and Metals (ICMM, 2016) was established in 2001 to act as a catalyst for (general) performance improvement in the mining and metals industry. It continues and encourages companies to be more willing to engage constructively with critics and to listen more carefully to what they have to say. There are numerous other national (e.g. MEND (1989) in Canada) or focused efforts such INAP (2002) covering acid mine drainage. As well, most of the professional bodies catering to mining and metals production have sustainability charters and active discussion and dissemination of development amongst their members. Despite the plethora of activity, there is a growing realisation that there are strong drivers for change. In 2012 the Kellogg
Innovation Network convened a diverse group of people to recognise that mining as we know it is dead and that a new approach is needed. The clear outcome after a year and a half of deliberation is that mining companies must become integrated development partners with all stake-holders: a most worthwhile message but not particularly new. The World Economic Forum in its annual meeting at Davos in 2014 similarly tackled the issue of mining sustainably. The briefing paper noted that ‘‘global markets remain weak following the global financial crisis, commodity prices have fallen, and shareholders are pushing for leaner operations and greater returns on investment. At the same time, the stakeholder landscape for mining and metals companies is becoming increasingly diverse, with growing expectations for companies to operate in a responsible and sustainable manner”. This is again not really a new message yet it still remains urgent enough to feature at Davos, even after the formation of the Global Mining Initiative in 2000. Rising concerns about artisanal mining, an intensified rate of technological change, abrupt generational change, a growing concern for the environment, increased ‘‘democratisation” and a higher demand for fairness are all likely to contribute to a redefining of values and a rethinking of the present multi-stakeholder model. There are many other examples of the ‘‘Mining as we know it is dead” theme, e.g. Hitch et al. (2015), some quite enlightening in terms of the solutions proposed. As already pointed out, mining companies must and do operate at some point on the scale between ‘‘staying out of jail” and pursuit of ‘‘perfection in sustainable mining”. What seems clear at a generic level is that leadership from management will continue to be critical but so will new technology. It is the author’s opinion that adoption of the technological initiatives outlined in the rest of this paper could deliver progress towards a much more sustainable and more economic mine of the future. 4. The mine of the future – deep underground There have been many visionary opinions of the mine of the future, not least from this author (2003). One suggestion is for a mine that is essentially not visible on the surface and only brings to the surface the primary material of value. If the surface footprint
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is to be negligible, then subsidence or interference with lakes is not allowable. Equally, interference with aquifers is also not permissible. The vision therefore suggests deep mineralizations that are exploited essentially by in-place leaching. An outcome of being more than 1 km deep and with no interference with the surface is that a mine is equally acceptable in an urban setting as in a remote area. This is quite some advantage in terms of finding the skills to develop and operate such a mine. It would be a very high-tech affair. To put such a step change into perspective, one might look at the industry over the last 200 years and note that there have been at least 3 transformative changes: Flotation, initially to recover zinc from waste material in 1902, albeit with some parallel developments a little earlier. Open pit mining (using massive steam shovels in a copper mine at Bingham Canyon in 1906). Solvent extraction – electrowinning, initially for uranium extraction in world war 2 and then for copper in the 1960s). Against this background, another transformative change is well due. Interestingly, there is significant progress in the technologies needed for deep underground in-place mining. One must explore, then access then stimulate the mineralization. On the question of exploration, many of the techniques developed for the oil and gas industry are relevant to mineral exploration and exploitation. The geophysical side has been noted by Sinclair and Thomson (2015) and was extensively reviewed at the In Situ Recovery conference in Adelaide organized by CSIRO and the University of Adelaide (Robinson and Grano, 2015); the papers on targeting and characterizing natural fractures being particularly relevant. If large-scale access is required to these deep mineralizations, then the automation of more conventional approaches will be a key to economic implementation. Automation of underground operations has been ongoing for many years, with LKAB one of the pioneers in the field in the late 1980s (Nilsson et al., 2001). Automation of existing processes in deep mines to 1.5 km is seen as fully practicable by 2030 (Bäckblom et al., 2010) and indeed the essential step towards subsequent winning of base metals beyond 2030 by in-situ production with zero waste and no human intervention. The Scandinavian countries are not the only groups to recognize the importance of deep underground mining to the future of mining. The Canadian Group on Ultra Deep Mining Network (UDMN, 2015) has garnered $46 m (including $16 m from the Canadian Government) to tackle developments. We can conceptually see the mine of the future from two evolutionary paths, albeit with convergence. One is from conventional underground mining where broken material is leached in-place and the other is from bores drilled to a mineralization which is fracked and then leached. To some extent the first is an evolution of existing mining methods and there are several examples of where broken material remaining in stopes has been leached (Sinclair and Thompson, 2015) but no examples yet of where this was the primary method of production. The second method is an evolution from the solution mining of uranium in sedimentary locations and applying the exploration, fracking and development methods of the oil and gas industry to hard rock mineralizations. Time will tell the most fruitful paths. Copper is an interesting case study. Since the discovery of Resolution in Arizona (Briggs, 2015) in 1995, this massive but deep porphyry system has shown the world what many have long suspected, that there is much potential for future mining of copper to be deep underground. At 2 km deep and a possible temperature of 80 °C, it is an obvious target for the mine of the future. Delineating such mineralizations will increasingly benefit from
advanced geophysical techniques, especially those developed for the oil and gas industries (Fraser, 2015). As Sinclair and Thomson (2015) have pointed out, there are examples of copper leaching underground as secondary operations. The presence of chalcopyrite per se is not seen as a limitation. It is a challenge in that both Eh and pH must be controlled to prevent passivation. Equally, the gangue material must be appropriate. High acid consumption or gypsum precipitation are known challenges although options are available. What is fundamentally interesting and hopeful for deep leaching is that as depths increase, so does pressure and hence oxygen solubility, likely giving much higher leaching rates (McDonald, 2015). As an example, oxygen solubility in water at surface is around 8 ppm but is 3570 ppm at 1 km. As McDonald has pointed out, while solubility decrease with temperature, above 300 K, solubility then increases again. Some of this ground is also covered by Vargas (2015) who goes on to point out that chemical pre-treatment can be used to enhance permeability. Vargas and co-workers have developed an experimental methodology for quantifying the implementation and economic considerations of in-situ mining (Bahamondez et al., 2016). 5. Permeability enhancement There have been many visionary opinions of the mine of the future, not least from this author (2003). One suggestion is for a mine that is essentially not visible on the surface and only brings to the surface the primary material of value. If the surface footprint is to be negligible, then subsidence or interference with lakes is not allowable. Equally, interference with aquifers is also not permissible. The vision therefore suggests deep mineralizations that are exploited essentially by in-place leaching. As Grano (2014) has indicated, there are real challenges in enhancing permeability to allow in-situ recovery: Most rock matrix may have ultralow permeability without natural fractures Need to target natural fractures (horizontal bore hole direction) Need hydraulic fractures to intersect with natural fractures Fractures extend in direction of maximum principle stress Natural fractures may be co-located with mineralization? Need to maintain fractures under leach conditions for months/ years Acid resistant proppant but stress an issue on fracture-proppant conductivity It is more likely that initial commercial operations for in-situ mining will be on material that is first block caved and then has the permeability further enhanced. In this respect there are some novel developments in drilling and blasting technology. Blasting has developed in recent years not just in terms of the velocity of detonation and the strength of the blast, but also with the next generation of electronic initiation that is wireless and can include delays up to 30 s. These developments have passed the alpha stage of testing and are now at the beta test stage with certain customers of Boyce (2015) initially targeting niche underground applications such as stranded ore and sublevel cave rings. As Boyce points out, wireless detonation is a game changer in that automated drilling and charging are a reality. Electronic ignition means that from a sub level, holes could be drilled for several levels and then with a single sequence, the rock initially cracked (or preconditioned) and then the broken rock further comminuted by gas pressure and reflection effects. As Boyce (2015) suggests, ‘‘such a hybrid method could be developed to create large underground reactors for leaching of minerals” (see Fig. 4).
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are many further enhancements possible on the road to in-place leaching and recovery. Without being prescriptive, developments may include: Much cheaper, automated small hole directional drilling s for permeability control s hydrothermal spallation and high voltage pulse breakage for permeability Real time tracking of lixiviate Chemical tracers and nanomachine measurements Much more tailored and exotic organisms and peptides (Vargas, 2015), e.g. s Metal accumulating bacteria (e.g. Delftia Acidovorans) s Gangue leaching (e.g. Ferroplasma acidamanus). 8. In summary
Fig. 4. High lift drawbell plus post conditioning concept. (Boyce, 2015).
As a step towards demonstrating ‘‘high fidelity” control of explosives, experiments are underway in a European copper mine with a high grade seam. The blasted material in the ‘‘reactor” will be leached in-situ as a bioleach.
One can argue that despite many years of attention to sustainability, mining as we know it is in need of significant change. The mine of the future is technically feasible today, albeit at a Technology Readiness level less than that required for large commercial projects. First major steps are likely to be in large, deep ore bodies such as porphyry copper mineralizations. Caving to produce a reactor of broken material and then in-place leaching with barriers in place is all seen as relatively close, years and not 10s of years.
6. Barriers are essential At a fundamental level, in-place leaching requires permeability but ideally the reactive zone does not want to be connected to any groundwater flows. This will be the case from time to time, especially in deeper mineralizations. In most cases however it is necessary to pump out more fluid for production than is added as injected leachate. This is not desirable as the excess must be bled off, treated and disposed of – hardly compatible with a ‘‘zero footprint mine of the future”. As well, one must cope with major long range fractures which can provide paths for short circuiting. Geostatic pressures must also be considered in that overpressuring can inadvertently result in the extension or opening of existing long range fractures. A more appropriate approach is to consider the use of barriers. In the oil and gas industry there is wide spread use of gel barriers to control the flow of sweep fluids, to prevent bypassing and to control production. The lack of application of barriers to date in in-place leaching is more a matter of experience for the industry rather than lack of suitable barriers. The silicate barriers used elsewhere have properties ideal for inplace leaching. It is well known that at reasonable silicate loadings, the gel time for a 3:2 ration sodium silicate to sulphuric acid can vary from under a minute at pH 5 to several hours at pH 2 (PQ Europe, 2016). This means that a solution can be prepared and then pumped into place with a viscosity that of water, the pumping ceased and the gel then forms. This is cheap and effective. In addition, fine particulates can be added that can react with any acid lixiviant that overpressures the gel barrier through inadvertent operations. Such particles can react to expand the gel making it ‘‘self-healing”. Hollitt and Batterham (2002) tested such a barrier to block off a paleochannel which had previously been sheet piled as part of protection for a dam wall built over the channel. The piling had corroded allowing water to start washing away the dam wall. The barrier was low cost, almost trivial to inject and was totally successful. 7. And even further into the future While advanced blasting and barrier technology will most likely first be applied in block caves, as more experience is gained there
Acknowledgments The author acknowledges the initiatives of the University of Adelaide and the CSIRO in forming a working group to help focus efforts on in-situ recovery technologies for metals. The meeting held by the group in Adelaide in December 2015 provided much of the recent material referred to in this paper, including the recent developments at Orica outlined by Stephen Boyce. The papers in the References are accessible through Dr Dave Robinson of CSIRO [email protected]. The contribution of Peter Seligman from Melbourne University to the data in Fig. 2 is gratefully acknowledged.
References ABC News, 2012. Government imposes fracking moratorium
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Europe, P.Q., 2016. Sodium and potassium silicates
Case Studies. Society of Mining, Metallurgy and Exploration, pp. 681–690 (Chapter 75). Reggio, R., Lane, A. 2012. Monitor Deloitte: Mining in Africa: How inclusive solutions can mitigate risk. p12.
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