Khai Trung Le talks to Dr John Thompson and Theo Henckens about recent perceptions around mineral exhaustion, and how each school of thought approaches the future of supply.

A recent volume of single-article journal Geochemical Perspectives looks to dispel the continuing theories of mineral exhaustion. It focuses on pinning down misconceptions regarding how resources – potentially valuable prospects for future extraction – and reserves – identified and feasible for extraction – are evaluated, and how the use of inaccurate figures brings unrealistic predictions of shortage. While dissenters may agree that problems arise from vague definitions of scarcity, many believe that inaction will hasten exhaustion, and point to the United Nation’s intergenerational equity principle, a preservationist stance that seeks to combat exhaustion in the interest of future generations.

Frown upside down

The division between resource economics schools of thought is, on the surface, an oddly emotive one. Are you a pessimist or an optimist? As we wrestle with an increasing human population and rising standards of living against finite natural resource reserves, are you drawn to predictions of social and economic collapse or forecasts of sustained community and lifestyle improvements?

Thoughts on resource economics are commonplace, from Reverend Thomas Malthus’ Essay on the Principle of Population (1798) to James Acheson’s The Lobster Gangs of Maine (1988). But mineral enthusiasts may be more familiar with The Limits of Growth, written by Donella and Dennis Meadows, Jørgen Randers and William Behrens III and published in 1972. This bestselling book charted computer simulations of economic and population growth with finite resource supplies. In particular, The Limits of Growth predicted that copper and aluminium would be exhausted in 1993 and 2003, respectively. Dr John Thompson, Professor of Environmental Balance for Human Sustainability and co-author of the April 2017 edition of Geochemical Perspectives, argues that The Limits of Growth supports the pessimistic resource economics theories that persist today. ‘It is still a widely used concept in both serious and popular literature – even at the BBC! There is no evidence of any decline.’

Theo Henckens, environmental consultant and researcher at the University of Utrecht, the Netherlands, told Materials World, ‘According to resource pessimists it is only a matter of time before supply cannot meet demand. Urgent measures need to be taken to slow down the extraction of the scarcest resources. Generally, resource optimists do not deny that mineral resources will be depleted gradually, but they have a strong belief that humanity will be able to cope with the effects.’

Underpinning mineral resource economics is the way resources and reserves are defined. Henckens stated that reserves are linked to proven existence, current market prices and existing technologies, and are otherwise regarded as known. But resource estimates are based on non-proven geological availability, future market prices and technological developments – it is near impossible to predict precise quantities. Thompson said, ‘Resource is well defined by regulatory bodies. But future and/or undiscovered resources are more difficult to define. The lack of understanding of these concepts, and the nature of the Earth in general, definitely present challenges and was much of the rationale behind the volume.’

In further comments to the Cornell Chronicle, Thompson said, ‘We often add reserves by doing more work to demonstrate economic viability. That can be drilling holes to increase our understanding, changing the technology or it could be simply that the price of a commodity has gone up. All of those factors can turn something from being an uneconomic resource to an economic reserve.’

Green copper

Compiling work between researchers from the University of Geneva, Switzerland, University of Grenoble Alpes, France, University of Michigan, USA, and consultants from Australia and Canada, the team’s volume focuses on copper, a mineral that saw reserves of less than 500 million tonnes in 1988 increase to 720 million tonnes in 2016, as estimates of identified and undiscovered copper resources have increased. Resources can be converted into reserves for numerous reasons including new technology, drilling activity making sites more viable or an increase in the price of commodities.

Although Thompson states that variables such as efficiency of material use, recycling and substitution among others makes predicting the timescale to exhaustion for minerals such as zinc and copper after 50–100 years difficult, he remains optimistic about the future. ‘I think it is more likely that we will see demand stabilising or even declining before we see resource exhaustion.’

While Henckens’ figures are not materially extravagant – ‘according to my estimates, zinc will be exhausted within around 100 years, and copper within 200 years’ – based on the expectation of a 3% annual extraction increase until 2050 before it stabilises, leading to an increase of three times the rate in 2017, Henckens has less faith in self-governance to protect against mineral exhaustion. ‘My assessment is that without an active policy to make scarce minerals more expensive, substitution and recycling will not increase sufficiently fast. The market does not reflect differences of scarcity yet. The time horizon of the price mechanism of the free market system is not adequate to reflect geological scarcity and to save sufficient resources for future generations.’

Henckens argues that the paper's authors have presented overly optimistic scenarios including ‘extracting copper not only from the continental crust but also from the sea floor, mining taking place until a depth of 3.3km, whereas mining deeper than 1km is unusual, and extracting from deposits with a concentration as low as 0.03%, around ten times less than the lowest concentration mined today. This cannot be used as a sound basis for global mineral resources policy.’

Two schools of thought

The authors conclude that ‘Earth contains a truly enormous amount of copper. Just how much of this material might be mined now or in the future is not known, but it is definitely much larger than currently available estimates of reserves and resources.’ But the volume also concludes that how long these commodities last is also determined by rate of consumption, recycling, technological advances in extraction and use and alternative minerals, ‘topics [that] are far beyond the scope of this volume, but are obviously just as important.’

And although each of these are also highlighted as significant factors by Henckens, he notes that ‘the problem of depletion of geologically scarce mineral resources is apparently not perceived as grave enough for an international agreement.’ It is hard to imagine where the two schools of thought meet without this happening first.

Geochemical Perspectives volume 6, number 1 can be read at bit.ly/2rfidiN. Theo Hencken’s dissertation, Managing raw materials scarcity: safeguarding the availability of geologically scarce mineral resources for future generations can be read at bit.ly/2pWG9CZ