Environmental Problems, Their Causes, and Sustainability 1

Some analysts contend that all we need to do toincrease supplies of a mineral is to extract lowergrades of ore. They point to the development of newearth-moving equipment, improved techniques for removingimpurities from ores, and other technologicaladvances in mineral extraction and processing.In 1900, the average copper ore mined in theUnited States was about 5% copper by weight. Todayit is 0.5%, and copper costs less (adjusted for inflation).New methods of mineral extraction may allow evenlower-grade ores of some metals to be used.But several factors can limit the mining of lowergradeores. One is the increased cost of mining and processinglarger volumes of ore. Another is the availabilityof fresh water needed to mine and process someminerals—especially in arid and semiarid areas. Athirdlimiting factor is the environmental impact of the increasedland disruption, waste material, and pollutionproduced during mining and processing (Figure 16-13).One way to improve mining technology is to usemicroorganisms for in-place (in situ, pronounced “in-SY-too”) mining. This biological approach removes desiredmetals from ores while leaving the surroundingenvironment undisturbed. It also reduces air pollutionassociated with the smelting of metal ores and reduceswater pollution associated with using hazardous chemicalssuch as cyanides and mercury to extract gold.Once a commercially viable ore deposit has beenidentified, wells are drilled into it and the ore is fractured.Then the ore is inoculated with natural or geneticallyengineered bacteria to extract the desired metal.Next the well is flooded with water, which is pumpedto the surface, where the desired metal is removed.Then the water is recycled.This technique permits economical extractionfrom low-grade ores that are used more as high-gradeores are depleted. Currently, more than 30% of all copperproduced worldwide, worth more than $1 billion ayear, comes from such biomining. If naturally occurringbacteria cannot be found to extract a particular metal,genetic engineering techniques could be used to producesuch bacteria.However, microbiological ore processing is slow.It can take decades to remove the same amount of materialthat conventional methods can remove withinmonths or years. So far, biological mining methods areeconomically feasible only with low-grade ore forwhich conventional techniques are too expensive.Can We Use Nanotechnology to ProduceNew Materials? Evaluating a New TechnologyThat May Change the WorldBuilding new materials from the bottom up byassembling atoms and molecules has enormouspotential but could have potentially harmfulunintended effects.Nanotechnology is using science and engineering at theatomic and molecular level to build materials withspecified properties from the bottom up. It involvesfinding ways to manipulate atoms and molecules assmall as 1–100 nanometers—billionths of a meter—wide. For comparison, your unaided eye cannot seethings smaller than 10,000 nanometers across and thewidth of a typical human hair is 50,000 nanometers.This atomic and molecular approach to manufacturinguses raw materials of abundant atoms such ascarbon, oxygen, and hydrogen and arranges them tocreate everything from medicines and solar cells to automobilebodies, hopefully with little environmentalharm and without depleting nonrenewable resources.One example is soccer-ball-shaped forms of carboncalled buckyballs.Nanotechnology scientists entice us with visionsof a molecular economy. They include a supercomputerthe size of a sugar cube that could store all the informationin the U.S. Library of Congress, biocompositematerials smaller than a human cell that would makeyour bones and tendons super strong, designer moleculesthat could seek out and kill only cancer cells,foam with nanoparticles that could provide superthermalinsulation, and windows, kitchens, and bathroomsthat never need cleaning. The list could go on.This research is in the early stages and tangible resultsare a decade away. But already nanotechnologyhas been used to develop stain-resistant and wrinklefreematerials for pants and sunscreens that block ultravioletlight.Nobel laureate Horst Stormer says, “Nanotechnologyhas given us the tools ...to play with the ultimatetoy box of nature—atoms and molecules. ...The possibilities to create new things appear limitless.”You might want to consider this rapidly emergingfield as a career choice.So what is the catch? What are some possible unintendedharmful consequences of nanotechnology? Oneconcern is that as particles get smaller they becomemore reactive and potentially more toxic because theyhave large surface areas relative to their mass. Anotheris that nanosize particles can get through the naturaldefenses of our bodies. They could easily reach thelungs and from there migrate to other organs, includingthe central nervous system, and to the bloodstream.In 2004, Eva Olberdorster, an environmental toxicologistat Southern Methodist University, found thatfish swimming in water loaded with buckyballs experiencebrain damage within 48 hours. Little is knownabout how buckyballs and other nanoparticles behavein the human body. But factories are churning outbuckyballs and these and other nanoparticles are startingto show up in products from cosmetics to sunscreensand in the environment.Many analysts say we need to do two things beforeunleashing widespread use of nanotechnology.http://biology.brookscole.com/miller14347