In This Issue
Spring Issue of The Bridge on Emerging Issues in Earth Resources Engineering
April 14, 2014 Volume 44 Issue 1

Emerging Issues in Earth Resources Engineering

Friday, April 18, 2014

Author: Mary P. Anderson Charles Fairhurst

Editors’ Note

Earth resources engineering (ERE) has roots in mining and petroleum engineering but more broadly is engineering applied to the discovery, development, and production of subsurface earth resources such as minerals, hydrocarbons, groundwater, and geothermal energy. Production of such resources includes mineral processing and the application of technology for environmental remediation. Earth resources engineers also apply technology to isolate industrial waste products (e.g., radioactive wastes and CO2) from the biosphere and to protect people and facilities from extreme events at the surface, both natural (e.g., earthquakes, severe weather, landslides, volcanic eruptions) and human-made.

Earth resources engineers are trained in one or more of the following disciplines: mining engineering, petroleum engineering, geological engineering, rock mechanics, geomechanics, hydrogeology, and geophysics. As in other branches of engineering, interdisciplinary interaction among engineers and scientists is at the core of ERE research, development, and application.

Problems in ERE occur at many different spatial and temporal scales. In most continental areas the Earth’s crust is approximately 40 km thick, but extraction of earth resources is restricted to the relatively shallow lithosphere—the deepest mine is 4 km and the deepest borehole 12 km. Traditionally, engineers work at relatively small spatial and temporal scales relevant to a specific site (e.g., a mine) or facility (e.g., a spoils pile), while earth scientists are concerned with much larger scales as they study whole Earth processes. However, in recent decades this distinction has blurred as engineers design on bigger scales and longer time periods (e.g., geological repositories for high-level radioactive waste) and earth scientists provide input on site-scale problems (Cornet 2014, Chapter 1; DOE 2007). 

In 2008 the NAE published a report on grand challenges for engineering (NAE 2008), which prompted the Academy’s ERE section to develop some grand challenges specific to ERE (NAE Section 11 2010). The six papers in this issue of the Bridge highlight some emerging issues in ERE related to those challenges. Four of the six papers discuss extraction of earth resources: energy resources (shale gas/oil and geothermal), minerals, and groundwater; the other two concern challenges of carbon sequestration to deal with the consequences of burning fossil fuels and geological repositories for high-level radioactive waste resulting from the production of nuclear energy.

Grand Challenges for Earth Resources Engineering

The overarching grand challenge for ERE is “to supply society with its essential needs for energy, minerals, and groundwater and to use the earth itself as a resource for protecting people and the environment” (NAE Section 11 2010, p. 3). This in turn comprises four specific challenges: (1) make the earth “transparent,” (2) quantify and engineer subsurface processes, (3) minimize the environmental footprint, and (4) protect people.

 “Transparent earth” implies the ability to “see” into the subsurface. It requires technologies capable of imaging the subsurface—analogous, in principle, to medical technologies for imaging the human body. With new technologies such as geophysical tomography and nuclear magnetic resonance (NMR) imaging from boreholes engineers can “see” into the subsurface, but it is still not possible to image in real time more than a few meters from a borehole or tens of meters ahead of a tunnel-boring machine, nor is there a cost-effective way to monitor the fracture systems that control the deformation of a rock mass and flow of groundwater.

Figure 1

Hydrologic, mechanical, thermal, and chemical processes in the subsurface are intricately coupled in complex interactions (Figure 1). These processes are important to the production of oil and gas and geothermal resources, exploration for mineral deposits (because the processes control the precipitation of minerals), design of minimally invasive borehole mining methods, subsurface storage of wastes, remediation of contaminated soils and groundwater, and earthquake prediction and control. Numerical models are essential tools to forecast the effects of subsurface processes, but the general lack of data and uncertainties involved dictate an approach designed to gain understanding and explore potential tradeoffs and alternatives, rather than make absolute predictions as in other branches of engineering (Starfield and Cundall 1988).

To minimize any adverse environmental effects, earth resources engineers develop and implement technologies to remediate and protect groundwater, surface water, soils, and the landscape both during and after extraction of earth resources. For example, remediation might include application of nanotechnology and numerical models of subsurface processes to help design implementation strategies.

Earth resources engineers strive to protect workers from hazards associated with extraction of earth resources and to protect people and essential facilities from adverse surface effects (Winquest and Mellgren 1988). The subsurface can be engineered to house urban infrastructures such as transportation corridors, water pipes, and electrical cables; and to store waste products, especially high-level radioactive waste.

The Long Transition to a Sustainable Future

Resource sustainability can be defined to mean that sufficient energy, mineral, and water resources will be available for future generations. Mineral and water resources are sustainable, whereas fossil fuels are not (Tinker et al. 2013). Furthermore, renewable energy resources are site-specific and currently supply only a small fraction of US energy needs: renewable energy (mainly hydroelectric and wind with lesser amounts of geothermal, solar, and biofuels) provided just 9 percent of US energy consumption in 2011, nuclear energy 8 percent, and fossil fuels 83 percent (DOE 2013a, Figure 52, p. 60).1 By 2040, renewables are predicted to contribute 13 percent, nuclear 9 percent, and fossil fuels 78 percent (DOE 2013a, Figure 52, p. 60). The transition to renewable sources of energy is under way but it will take many decades. During this transition to a new energy future, it is essential that hydrocarbons and nuclear resources be developed in a manner that protects people and the environment.

In this issue, Roland Horne and Jefferson Tester (2014) review the current status and potential of geothermal energy; especially promising are geothermal reservoirs enhanced by induced fracturing. Widespread use of renewable energy is in the future but in the meantime technological advances may spur further exploitation of fossil fuels. For example, the recent development of gas and oil from low-permeability shales, made possible by new technology for horizontal drilling and hydraulic fracturing, has fundamentally transformed the world’s immediate energy future by turning vast unconventional gas resources into reserves, as described by Mark Zoback and Douglas Arent (2014).

With recycling, substitution, and the potential for mining the ocean and ocean floor, the Earth’s supply of minerals is enormous and may be limitless (Price 2013). However, mineral deposits are dependent on geology and are not evenly distributed around the world. Leigh Freeman and R. Patrick Highsmith (2014) use socioeconomic arguments to show that development of mineral resources, while essential to the well-being of society, comes at a nonnegligible price to both the environment and society. Addressing those environmental and societal concerns in a complex international political and social milieu is a critical challenge for earth resources engineers, as is remediation of damage from past mining operations and minimization of such effects in the future.

Water is a renewable resource, limitless in principle, but one that requires sound management (Bredehoeft 2013). Groundwater resources will become increasingly important in providing clean water for drinking as well as industrial and agricultural uses. Groundwater use will also increase if droughts become more prevalent as a result of climate change. In this issue John Bredehoeft and William Alley (2014) explain the challenges of managing groundwater systems subject to a long response time—potentially hundreds of years—from the time pumping begins until a new sustainable equilibrium is established.

Requirements to mitigate adverse effects of resource development—such as loss of water from rivers and wetlands as a result of groundwater pumping, and contamination from the subsurface disposal of high-level radioactive waste, drilling fluids, and mining byproducts (waste rock, slurry, and water)—bring about additional challenges. Two articles address global-scale waste disposal problems.

Sally Benson and Julio Friedmann (2014) discuss subsurface storage of carbon dioxide generated by hydrocarbon-burning power plants as well as possibilities for CO2 utilization. While carbon capture and storage (CCS) would have to be implemented on a massive scale just to slow climate change, the authors make the case that CCS could be an important part of a global response to changing climate.

John Cherry, William Alley, and Beth Parker (2014) examine the long-standing problem of disposal of spent fuel and other high-level waste (HLW) from nuclear power production. All of the more than 30 countries that have stockpiles of HLW have opted for isolation in subsurface geological repositories. In the United States the geological repository at the Waste Isolation Pilot Plant (WIPP) site in Carlsbad, New Mexico, has stored transuranic (intermediate-level, long-lived radioactive) waste since 1999, and Finland, France, and Sweden are far advanced in developing HLW sites (although none has yet opened). The US Nuclear Regulatory Commission requires isolation of HLW for one million years—much longer than the current existence of the human race! Formulating a risk assessment strategy to guarantee isolation in a subsurface repository on the scale of geologic time is a formidable challenge facing earth resources engineers.

We hope this collection of papers will inform readers of the scope and importance of ERE and also stimulate interest in the challenges and opportunities ahead.

Acknowledgments

We thank Bill Alley, Lyn Arscott, Brian Clark, Brent Hiskey, Roland Horne, Yannis Yortsos, and Mark Zoback for providing helpful comments on a draft of this introduction. We also thank the following who each reviewed one of the papers in this issue: Lyn Arscott, Grant Ferguson, Steven Gorelick, Brent Hiskey, Erik Webb, and one anonymous reviewer.

References

Benson SM, Friedmann SJ. 2014. Carbon dioxide capture, utilization, and storage: An important part of a response to climate change. The Bridge 44(1):42–50.

Bredehoeft J. 2013. US water resources: Cleaner, and more valuable. In: The Impact of the Geological Sciences on Society, Special Paper 501. Bickford ME, ed. Boulder: Geological Society of America. pp. 53–68.

Bredehoeft JD, Alley WM. 2014. Mining groundwater for sustained yield. The Bridge 44(1):33–41.

Cherry JA, Alley WM, Parker BL. 2014. Geologic disposal of spent nuclear fuel: An earth science perspective. The Bridge 44(1):51–59.

Cornet FH. 2014 (in press). Elements of Crustal Geomechanics. Cambridge, UK: Cambridge University Press.

DOE [US Department of Energy]. 2007. Basic research needs for geosciences: Facilitating 21st century energy systems. Report from the workshop held February 21–23. Sponsored by the DOE Office of Basic Energy Sciences. Available at science.energy.gov/~/media/bes/pdf/reports/files/geo_rpt. pdf.

DOE. 2013a. Annual Energy Outlook 2013 with projections to 2040. DOE/EIA-0383. Available at www.eia.gov/forecasts/aeo/pdf/0383(2013).pdf.

DOE. 2013b. International Energy Outlook 2013. DOE/EIA-0484. Available at www.eia.gov/forecasts/ieo/pdf/0484(2013).pdf.

Freeman LW, Highsmith RP. 2014. Supplying society with natural resources: The future of mining—From Agricola to Rachel Carson and Beyond. The Bridge 44(1):24–32.

Horne RN, Tester JW. 2014. Geothermal energy: An emerging option for heat and power. The Bridge 44(1):7–15.

NAE [National Academy of Engineering]. 2008. Grand Challenges for Engineering. Available at www.engineeringchallenges.org/cms/8996/9221.aspx.

NAE Section 11. 2010. Grand Challenges in Earth Resources Engineering. Available at https://www.nae.edu/106328.aspx.

Price J. 2013. The challenges of mineral resources for society. In: The Impact of the Geological Sciences on Society, Special Paper 501. Bickford ME, ed. Boulder: Geological Society of America. pp. 1–20.

Starfield AM, Cundall PA. 1988. Towards a Methodology for Rock Mechanics Modelling. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts 25(3):99–106.

Tinker SW, Lynch H, Carpenter M, Hoover M. 2013. Global energy and the role of geosciences: A North American perspective. In: The Impact of the Geological Sciences on Society, Special Paper 501. Bickford ME, ed. Boulder: Geological Society of America. pp. 21–52.

Winquest T, Mellgren KE. 1988. Going Underground. Stockholm: Royal Swedish Academy of Engineering Sciences.

Yow J, Hunt J. 2002. Coupled processes in rock mass performance with emphasis on nuclear waste isolation. International Journal of Rock Mechanics and Mining Sciences 39(2):143–150.

Zoback MD, Arent DJ. 2014. Shale gas development: Opportunities and challenges. The Bridge 44(1):16–23.

FOOTNOTES

1 DOE (2013b) provides information about current and projected global energy use.

About the Author:Mary P. Anderson (NAE) is professor emerita, Department of Geoscience, University of Wisconsin-Madison. Charles Fairhurst (NAE) is senior consultant, Itasca Consulting Group, Minneapolis, and professor emeritus, Department of Civil Engineering, University of Minnesota.