After completing this chapter, you will be able to:Describe the global and Canadian production and use of metals, fossil fuels, and other non-renewable resources.Explain the heavy reliance of industrialized economies on non-renewable resources, and predict whether these essential sources of materials and energy will continue to be readily available into the foreseeable future.Outline five major sources of energy that are available for use in industrialized countries, and describe the potential roles of these in a sustainable economy.Introduction
As we noted in Chapter 12, the reserves of non-renewable resources are inexorably diminished as they are extracted from the environment and used in the human economy. This is because non-renewable resources are finite in quantity and their stocks do not regenerate after they are mined. Note that the word reserve has a specific meaning here – it is used to denote a known amount of material that can be economically recovered from the environment (that is, while making a profit).
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Of course, continuing exploration may discover previously unknown deposits of non-renewable resources. If that happens, there is an increase in the known reserves of the resource. For example, the world’s known reserves of nickel and copper have been increased during the past two decades because of the discovery of rich deposits of those metals in northern Quebec and Labrador. There are, however, limits to the number of “new” discoveries of non-renewable resources that can be made on planet Earth.
Changes in the value of non-renewable commodities also affect the sizes of their economically recoverable reserves. For example, if the value of gold increases in its marketplace, then it may become profitable to prospect for new stocks in remote places, to mine lower-grade ores, and to reprocess “waste” materials containing small quantities of this valuable metal. An improvement of technology may have the same effect, for instance, by making it profitable to process ores mine that were previously non-economic.
In addition, the life cycle in the economy of some non-renewable resources, particularly metals, can be extended by recycling. This process involves collecting and processing disused industrial and household products to recover reusable materials, such as metals and plastics. However, there are thermodynamic and economic limits to recycling, which means the process cannot be 100% efficient. Furthermore, the demand for non-renewable resources is increasing rapidly because of population growth, spreading industrialization, and improving standards of living along with the associated per-capita consumption. This has resulted in an accelerating demand for non-renewables that must be satisfied by mining additional quantities from the environment.
The most important classes of non-renewable resources are metals, fossil fuels, and certain other minerals such as gypsum and potash. The production and uses of these important natural resources are examined in the following sections.Metals
Metals have a wide range of useful physical and chemical properties. They can be used as pure elemental substances, as alloys (mixtures) of various metals, and as compounds that also contain non-metals. Metals are used to manufacture tools, machines, and electricity-conducting wires; to construct buildings and other structures; and for many other purposes. The most prominent metals in industrial use are aluminum (Al), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), mercury (Hg), nickel (Ni), tin (Sn), uranium (U), and zinc (Zn). The precious metals gold (Au), platinum (Pt), and silver (Ag) have some industrial uses (such as conductors in electronics), but are valued mostly for aesthetic reasons, particularly to manufacture jewelry. Some of the more common metal alloys are brass (containing at least 50% Cu, plus Zn), bronze (mostly Cu, plus Sn and sometimes Zn and Pb), and steel (mostly Fe, but also containing carbon, Cr, Mn, and/or Ni). Metals are mined from the environment, usually as minerals that also contain sulphur or oxygen. Deposits of metal-bearing minerals that are economically extractable contribute to the known reserves of metals. An ore is an assortment of minerals that are mined and processed to manufacture pure metals. The stages in metal mining, processing, manufacturing, and recycling are summarized in Figure 13.1.
Figure 13.1. Metal Mining and Use. This diagram shows major stages of the mining, manufacturing, use, and re-use of metals, as well as the associated emissions of waste gases and particulates to the environment. Overall, the diagram represents a flow-through system, with some recycling to extend the lifetime of metals within the economy. Source: Modified from Freedman (1995).
Ore extraction by mining is the initial step in the process of bringing is metals into the material economy. This may be conducted in surface pits or strip mines, or in underground shaft-mines that may penetrate kilometers underground. In an industrial facility called a mill, the ore is crushed to a fine powder by heavy steel balls or rods within huge rotating tumblers. The ground ore is then separated into a metal-rich fraction and a waste known as tailings. Depending on the local geography, the waste tailings may be discarded onto a contained area on land, into a nearby lake, or into the ocean (see Chapter 18).
If the metal-rich fraction contains sulphide minerals, it is next concentrated in a smelter by roasting at high temperature in the presence of oxygen. This releases gaseous sulphur dioxide (SO2) while leaving the metals behind. The concentrate from the smelter is later processed into pure metal in a facility called a refinery. The pure metal is then used to manufacture industrial and consumer products. The SO2may be processed into sulphur or sulphuric acid that can be used in various other industrial processes, or it may be released to the environment as a pollutant.
After the useful life of manufactured products has ended, they can be recycled back into the refining and manufacturing processes, or they may be discarded into a landfill.
High-quality ores are geologically uncommon. The deposits that are most economic for mining are typically located fairly close to the surface, and the ores have a relatively high concentration of metals. However, the thresholds vary depending on the value of the metal being processed. Ores with very small concentrations of gold and platinum can be economically mined because these metals are extremely valuable (per unit of weight). In contrast, less-valuable aluminum and iron must be mined as richer ores, in which the metals are present in high concentrations.
Data showing the global production of industrially important metals are given in Table 13.1. Note that for most metals the amounts consumed are somewhat larger than the annual production; this indicates that some of the consumption involves recycled material that has been reclaimed from previous uses. Also note the large increase in production of most metals since 1977. Iron and aluminum are the metals produced and used in the largest quantities. The life index (or production life, calculated as the known reserves divided by the annual rate of production) of aluminum is about 592 years, and for iron ore it is 58 years (Table 13.1). Life indexes for other metals listed in the table are less, which suggests that their known reserves are being quickly depleted. It is important to remember, however, that those known reserves are increased by new discoveries, changes in technology, and more favourable economics for the resource.
Table 13.1. Global Production, Consumption, and Reserves of Selected Metals. Data from: U.S. Bureau of Mines (1977) and U.S. Geological Survey (2014).
Canada is one of the world’s leading producers of metals, accounting for 15% of the global production of nickel in 2006, 9% of aluminum, and 6% zinc (Tables 13.1 and 13.2). Much metal production is intended for export. Domestic consumption is about 39% of the value of production of all metals (Table 13.2). Metal-ore mining contributed $17-bilion to the GDP of Canada in 2011, and support activities (such as prospecting) another $4-billion, for a total of 1.3% of the GDP (Statistics Canada, 2014a).
The reserve life (life index) of Canadian reserves of metals is similar to or shorter than their global values (Table 13.2). Canadian reserves make up 15% of the global reserves of uranium and 5–10% of those of cadmium, nickel, silver, and zinc.
Table 13.2. Reserves, Production, and Consumption of Selected Metals in Canada, 2012. Note that bauxite (aluminum ore) is not mined in Canada, but large amounts are imported for processing. Data from: Natural Resources Canada (2014a) and U.S. Geological Survey (2014).
Table 13.3. Provincial Production of Selected Metals in Canada, 2013. Data from: Natural Resources Canada (2014a).
Fossil fuels include coal, petroleum, natural gas, oil-sand, and oil-shale. These materials are derived from the partially decomposed biomass of dead plants and other organisms that lived hundreds of millions of years ago. The ancient biomass became entombed in marine sediment, which much later became deeply buried and eventually lithified into sedimentary rocks such as shale and sandstone. Deep within those geological formations, under conditions of high pressure, high temperature, and low oxygen, the organic matter transformed extremely slowly into hydrocarbons (molecules that are composed only of carbon and hydrogen) and other organic compounds. In some respects, fossil fuels can be considered to be a form of stockpiled solar energy – sunlight that was fixed by plants into organic matter and then stored geologically.
Image 13.1. Because petroleum and other fossil fuels are non-renewable resources, their future reserves are diminished when they are extracted from the environment. This is an oil pump in southeastern Saskatchewan. Source: B. Freedman.
In a geological sense, fossil fuels are still being produced today, by the same processes that involve dead biomass being subjected to high pressure and temperature. Because the natural geological production of fossil fuels continues, it might be argued that these materials are a kind of renewable resource. However, the rate at which fossil fuels are being extracted and used is enormously faster than their extremely slow regeneration. Under this circumstance, fossil fuels can only be regarded as being non-renewable.
Hydrocarbons are the most abundant chemicals in fossil fuels. However, many additional kinds of organic compounds may also be present, which incorporate sulphur, nitrogen, and other elements in their structure. Coal in particular is often contaminated with many inorganic minerals, such as shale and pyrite.
The most important use of fossil fuels is as a source of energy. They are combusted in vehicle engines, power plants, and other machines to produce the energy needed to perform work in industry, for transportation, and for household use. Fossil fuels are also used to produce energy to heat indoor spaces, an especially important function in countries with a seasonally cold climate. Another key use is for the manufacturing of synthetic materials, including almost all plastics. In addition, asphaltic materials are used to construct roads and to manufacture roofing shingles for buildings.
Coal is a solid material that can vary greatly in its chemical and physical qualities. The highest quality coals are anthracite and bituminous, which are hard, shiny, black minerals with a high energy density (the energy content per unit of weight). Lignite is a poorer grade of coal, and it is a softer, flaky material with a lower energy density. Coal is mined in various ways. If deposits occur close to the surface, they are typically extracted by strip-mining, which involves the use of huge shovels to uncover and collect the coal-bearing strata, which are then transported using immense trucks. Deeper deposits of coal are mined from underground shafts, which may follow a seam kilometers into the ground. Most coal in North America is extracted by strip-mining.
After it is mined, coal may be washed to remove some of the impurities and then ground into a powder. Most is then combusted in a large industrial facility, such as a coal-fired generating station, a use that accounts for about half of the global use of coal and 88% in Canada (Natural Resources Canada, 2014b). In addition, about 75% of the world’s steel is manufactured using coal as an energy source, often as a concentrated material known as coke. Coal can also be used to manufacture synthetic petroleum.
Petroleum (crude oil) is a fluid mixture of hydrocarbons with some impurities, such as organic compounds that contain sulphur, nitrogen, and vanadium. Petroleum from different places varies greatly, from a heavy tarry material that must be heated before it will flow, to an extremely light fluid that quickly volatilizes into the atmosphere. Petroleum is mined using drilled wells, from which the liquid mineral is forced to the surface by geological pressure. Often, the natural pressure is supplemented by pumping.
A heavy form of petroleum called bitumen is also produced by mining and refining oil- sand, which is extracted in northern Alberta. Oil-sand deposits that are close to the surface are mined in immense open pits, while deeper materials are treated with steam so they will flow and are then extracted as a heavy liquid using drilled wells.
Once extracted, petroleum is transported by overland pipelines, trucks, trains, and ships to an industrial facility known as a refinery, where the crude material is separated into various constituents. The fractions may be used as a liquid fuel, or they can be manufactured into many useful materials, such as plastics and pigments. The refined fractions include the following:a light hydrocarbon mixture known as gasoline, which is used to fuel automobilesslightly heavier fractions, such as diesel fuel used by trucks and trains and a home-heating fuelkerosene, which is used for heating and cooking and as a fuel for airplanesdense residual oils, which are used as a fuel in oil-fired power plants and in large shipssemi-solid asphalts that are used to pave roads and manufacture roofing products
Natural gas is also extracted using drilled wells. The dominant hydrocarbon in natural gas is methane, but ethane, propane, and butane are also present, as often is hydrogen sulphide. Most natural gas is transported in steel pipelines from the well sites to distant markets. Sometimes it is liquefied under pressure for transportation, particularly by ships. In Canada, however, it is distributed mostly through an extensive network of pipelines. Natural gas is used to generate electricity, to heat buildings, to cook food, to power light vehicles, and to manufacture nitrogen fertilizer.
Image 13.2. Continued exploration for non-renewable resources can discover new reserves. Because Earth is finite, however, there are limits to these discoveries, which are being approached rapidly. This enormous off-shore production platform was constructed to develop the Hibernia petroleum deposit on the Grand Banks off Newfoundland. Source: Dosya: Hibernia platform, Wikipedia Commons;http://tr.wikipedia.org/wiki/Dosya:Hibernia_platform.jpg
Production, Reserves, and Consumption
The global production and reserves of fossil fuels are shown in Table 13.4. The production of petroleum increased by 29% between 1993 and 2013, natural gas by 64%, and coal by 83%. There is active exploration for all these fuels, and additional reserves are being discovered in various regions of the world. Fossil fuels are, however, being consumed extremely rapidly, particularly in developed and rapidly developing economies. Consequently, the expected lifetimes of the known reserves are alarmingly short, equivalent to 113 years for coal, 55 years for natural gas, and 58 years for petroleum.
These numbers should not be interpreted too literally, however, because ongoing exploration is discovering additional deposits, which add to the known reserves. This is illustrated by changes in the calculated reserve life of petroleum, which was 46 years in 1993, but twenty years later had actually increased to 58 years. Of course, this seemingly unexpected result is due to the fact that previously unknown reserves of petroleum had been discovered during that 20-year period, or rising prices had made once-uneconomic resources viable (such as the oil-sands of Alberta). Nevertheless, the discoveries will be limited by the finite amounts present on Earth, so the fact remains that the stocks of these non-renewable resources are being depleted rapidly.
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Table 13.4. Global Production and Reserves of Fossil Fuels, 2013. “Proven” reserves are the total amounts of a resource that are known to exist. The reserve life is the reserves divided by the annual rate of extraction. Source: Data from British Petroleum (2014).