Environmental Problems, Their Causes, and Sustainability 1

Separationof ore fromgangueMetal oreSurfaceminingSmeltingRecyclingScattered in environmentMeltingmetalConversionto productDiscardingof productFigure 16-15 Typical life cycle of a metal resource. Each step in this process uses energyand produces some pollution and waste heat.centive to reduce resource waste and pollution. Environmentalistsand some economists call for phasing infull-cost pricing—including the cost of environmentalharm done in the price of goods made from minerals.xHOW WOULD YOU VOTE? Should market prices of goodsmade from minerals include their harmful environmental costs?Cast your vote online at http://biology.brookscole.com/miller14.Aperts disagree about depletion times, theyare often using different assumptions aboutsupply and rate of use (Figure 16-16).The shortest depletion time assumesno recycling or reuse and no increase in reserves(curve A, Figure 16-16). A longer depletiontime assumes that recycling willstretch existing reserves and that bettermining technology, higher prices, and newdiscoveries will increase reserves (curve B,Figure 16-16). An even longer depletiontime assumes that new discoveries will furtherexpand reserves and that recycling,reuse, and reduced consumption will extendsupplies (curve C, Figure 16-16). Findinga substitute for a resource leads to a newset of depletion curves for the new resource.We can use geological methods tomake fairly good estimates of the reservesof most resources (Figure 16-10, blue) andless accurate measurements of potentialother supplies of mineral resources (Figure16-10, red). Rising prices and improvedmining technology can convertsome of the other resources to reserves,but it is difficult to make accurate projectionsof how much this will add to the usablesupply.Mine, use, throw away;no new discoveries;rising prices16-7 SUPPLIES OF MINERALRESOURCESWill We Have Enough Nonrenewable MineralResources? Making Educated GuessesThe future supply of a resource depends on itsavailable and affordable supply and how rapidlythat supply is used.The future supply of nonrenewable minerals dependson two factors. One is the actual or potential supply ofthe mineral and the other is the rate at which we use it.We never completely run out of any mineral.However, a mineral becomes economically depletedwhen it costs more to find, extract, transport, andprocess the remaining deposit than it is worth. At thatpoint, there are five choices: recycle or reuse existing supplies,waste less, use less, find a substitute, or do without.Depletion time is how long it takes to use up a certainproportion—usually 80%—of the reserves of a mineralat a given rate of use (Figure 1-8, p. 11). When ex-ProductionPresentBDepletiontime ACRecycle; increase reservesby improved miningtechnology, higher prices,and new discoveriesDepletiontime BTimeRecycle, reuse, reduceconsumption; increasereserves by improvedmining technology,higher prices, andnew discoveriesDepletiontime CFigure 16-16 Depletion curves for a nonrenewable resource (suchas aluminum or copper) using three sets of assumptions. Dashedvertical lines represent times when 80% depletion occurs.http://biology.brookscole.com/miller14345