Encyclopedia of Global Resources part 146 ppt

Woody material is produced in many plants, but its most usefulmanifestation isin thelimbs andtrunks of trees. There is a great diversity of tree species, and most climatic zones have at least one thathas adapted to the prevailing conditions within that area. Thus wood is generally available in most inhabited regions of the world. Wood has played a dominant role as a construction and engineering material in human society, yethumankind has livedwith this materialfor so long that its significance is easily overlooked. Hardwoods and Softwoods Trees are broadly classified into hardwoods and softwoods. These terms can be misleading, since they are not connected to the actual hardness of the wood. Hardwoods are broad-leaved deciduous trees. Soft- woods, on the other hand, have narrow, needlelike leaves andare usuallyevergreen. Oak,birch, and basswood are common hardwood species, whereas long- leaf pine, spruce, and cypress are softwoods. Some hardwoods (oak) are actually hard. Many others (basswood) are actually softer than the average softwood. In fact, balsa is classified as a hardwood even though it is one of the softest woods in the world. By farthe majority oftimber used inbuilding structures comes from the softwood category. Douglas fir, southern pine, and redwood are some of the impor - tant softwood species widely employed in structural applications. They are relatively strong and can be used in structural elements such as joists, beams, and columns. By comparison, the stronger hardwood species, such as oak, are relatively heavy, hard to handle, and hard to nail. As far as construction is concerned, their utility is limited; they are generally used only in flooring, cabinetry, and furniture. Supply and Disposal Wood is arenewable resource. Itdoes not existinfinite quantities;rather,it is constantly produced in growing trees. If forests are carefully man- aged, timber can be harvested on a sustained-yield basis year after year. Wood is also a reusable resource. The recycling of timber from old buildings is well documented. The ease with which wood can be cut, joined, and worked into various shapes permits the extension of its functional life beyond that of many other construction materials. Wood is a biodegradablenatural product: It can be reduced to its constituent carbohydrates and extract- ives through degradation. Afterwood hasreached the end of its useful service, it can be disposed of with little damage to the environment. Unlike plastics or chemicals, timberhasa very lowpollutionpotential. A study quantified the pollution potential of various construction materials, finding that steel is five times more polluting than timber, while aluminum and concrete blocks are respectively fourteen and twenty- four times more polluting. From an environmental standpoint, timber is recognized as the most appro- priate construction and engineering material. Logging Tremendous quantities of timber are consumed each year throughout the world. An average of about 3.5 billion cubic meters of timber is harvested annually. The majority of hardwood harvest is used for fuel, while softwoods are primarily used in construction and manufacturing. To produce the large quantities of timber needed annually, logging operations have become highly organized and technologically ad - vanced. When trees are removed in harvest, steps are taken to provide for forest renewal and to prevent 1356 • Wood and timber Global Resources A pile of timber ready for processing. (©Vadimb/Dreamstime.com) soil erosion. Such steps include leaving some trees to produce seeds, transplanting young trees, and other methods of reseeding. Sometimes a “prelogging” operation is undertaken before the main harvest. In this phase, thesmall trees are removed forconversion into poles, posts, and pulpwood. During harvest, various types of machinery are used to cut trees close to the ground. The limbs are then removed from the fallen trees and the trunks are bucked into various lengths and transported to sawmills for further processing. The remaining tree limbs are converted intochips for sale to pulp and paper mills. Frequently roads are built to facilitate the transportation of trunks and the deployment of heavy logging equipment. At the con- clusion of harvest, refuse should be disposed of so that itwillnot interfere withthegrowth ofnew trees. Owing to careful management of forests and improved efficiency of logging operations, the supply of timber in the UnitedStates currently renews itself at a higher rate than the removal level. It must be pointed out, however, that growth in world population will in- evitably bring about an increase in timber consumption. The adequacy of timbersupply will be amatter of concern in the future. Physical Structure and Strength As a material of botanical origin, wood is composed of hollow, elongated fibers. These fibers are usually arranged parallel with one another in the direction of the length of the trunk. They are cemented together by a substance known as lignin. The fibers in softwoods are longer than those in hardwoods. The length of the fibers, however, is not a criterion of the strength of the wood. Owing to the parallel arrange- ment of their fibers, wood possesses different me- chanical properties in different directions and is said to be anisotropic. As an example, timber is five to ten times as strong in compression parallel to the grain as it is perpendicular to the grain. The varying strength of timber in different directions must be taken into consideration in construction design. By contrast, metals are isotropic, having the same characteristics in any direction. The strength of timber is affected by its moisture content. Wood in a living tree typically contains more moisture than the surrounding atmosphere. When a piece of timber is cut from the log and exposed to air, its moisture content decreases to an equilibriumvalue determined by the temperature and relative humidity of ambient air. Should wood dry below a value called the “fiber saturation point,” it becomes stronger and stiffer. That is why higher design stresses are allowed for timber which is used under relatively dry conditions, such as a girder in a building, than for timber used under relatively moist conditions,such asin a wa- terfront house or in a bridge. Wood has a high strength-to-weight ratio. Com- pared with many other construction materials, wood, pound for pound, is stronger. For instance, in bend- ing tests, Douglas fir has a strength-to-weight ratio Global Resources Wood and timber • 1357 U.S. Lumber Consumption (billions of board feet) 1995 2000 2003 2005 2007 Species group Softwoods 47.6 54.0 56.5 64.4 50.5 Hardwoods 11.7 12.2 10.5 11.2 10.3 End use New housing 15.9 20.6 24.0 28.6 26.2 Residential 14.3 16.4 18.3 20.6 20.9 New nonresidential construction 5.8 5.1 4.4 4.3 3.9 Manufacturing 5.5 — 8.1 7.7 7.3 Shipping 8.5 7.4 7.5 7.6 7.7 Other 9.3 16.1 4.7 7.0 — Source: U.S. Forest Service, U.S. Timber Production, Trade, Consumption, and Price Statistics, 1965-1999 and U.S. Department of Commerce, Statistical Abstract of the United States, 2009, 2009. which is 2.6 times that of low-carbon steel. Wood also has very high internal friction within its fibrous structure and is therefore a good absorber of vibrations. It has much greater damping capacity than other materials, particularly the metals. That explains why wood is the preferred material for construction of houses in earthquake-prone regions. Finally, timber structures can be designed to withstand impact forces that are twice as large as those they can sustain under static conditions. Materials such as steel and concrete do not permit such increase in the applied forces. This exceptional impact strength of wood is utilized in timber structures such as bridges and the landing decks of aircraft carriers. Insulation and Fire Resistance Because of its fibrous composition, wood has excellent insulating properties. At a low moisture content, wood is classified as an electricalinsulator.This iswhat makes wood sucha commonmaterial forhigh-voltage power-line poles and for tool handles. Wood is also an effective thermal insulator. The thermal conductivity of timber is only a fraction of that of metals and other common construction materials. For example, bricks are about 6 times more conductive than timber, and glass and steel are respectively 8 and 390 times more conductive. By utilization of stud walls or layers of spongy materials, thermal insulation of timber structures can be further enhanced. In addition, timber structures may be designed to provide a degree of acoustical insulation. Sound is transmitted through vibration of air particles. Because of its high vibration- damping capacity, wood is also a good acoustical insulator. It is well known that wood is combustible. On the other hand, wood that isthick enough is alsofire resistant. Because of thelow thermal conductivity ofwood, the high temperatures of a fire cause a temperature rise for only a short distance into the wood from the surface exposed to the fire. This is the reason larger timber members may continue to support a structure in a fire long after an insulated steel member has collapsed because of elevated temperatures. In fact, buildings framed with large timber members have been given the highest rating by fire underwriters among all common buildings erected. Fabrication and Workability Wood may be cut and worked into various shapes with the aid of simple hand tools or with power-driven ma - chinery. It therefore lends itself not only to conver - sion in a factory but also to fabrication on site. It is the latter fact that principally keeps conventional wood- frame construction fully competitivewith anymethod of prefabrication of houses yet employed. Timber can be joined with nails, screws, bolts, and connectors, all of which require the simplest kinds of tools and produce strong joints. Timber may also be joined with adhesives, which can produce a continu- ous bond over the entire surface to which they are applied and develop the full shear strength of the solid timber. This use of adhesives provides a means of fab- ricating timber members of different shapes and al- most unlimited dimensions. The prefabrication of large wood trusses, laminated beams and arches, and stress-skin panels has permitted wood to remain ex- tremely competitive as a building and engineering material. Durability Wood is remarkably resistant to decay and is inert to the action of most chemicals. It is widely used in facili- ties for bulkchemical storage;the timber may be indi- rect contact with the chemicals. When wood is exposed to atmospheric conditions, it slowly erodes under the action of weather at arate of about 0.64 cen- timeter per century. There is no reason why, if properly used, wood should not last for a long time. Decay and insect damage are often significant problems, but these can be minimized by following sound methods of design in construction and by using properly sea- soned timber. In situations where biological wood- destroying agencies are difficult to control, the decay resistance of timber can be maintained by impregna- tion with suitable preservatives. Untold numbers of well-designed bridges and buildings made entirely or partly of wood have served satisfactorily for long periods with little maintenance. Many that are more than a century old are still in service, whereas others, although in satisfactory condi- tion, have been altered or replaced to meet more stringent modern building codes. If years of satisfactory service are a measure of durability, few construction materials can rival timber. Significance of Wood Wood has remained a primary construction material for thousands of years essentially because no competi - tive material has all the advantages of wood. No other natural substance can meet the ever-increasing de - 1358 • Wood and timber Global Resources mands of modern society for paper and other pulp products. It is also unlikely that a synthetic material can be made that can compete economically with wood as a source of pulp, particularly in the light of the limited supply and high cost of petroleum. On the other hand, methods for converting wood into various chemicals are continually in development. There is potential for using wood as a raw material to produce chemicals that are now obtained from petroleum. Future Prospects Tremendous progress has been madein transforming wood from a material of craftsmanship to one of engineering. Reliable structural grading, improved fastenings, efficient fabrication, and glue-laminating have all contributed to making wood a modern construction material. Timber connectors and other improve- ments in fastenings have permitted the use of small timber members for larger spans. It is expected that even better methods of fastening will be developed so that long, clear-span timber trusses will become common sights in new buildings. The increasing popularity of glue-laminating is of particular significance. A glue-laminated timber member typically has greater strength than a solid sawed member of the same size. It may also have superior surface properties such as higher fire resistance. The laminated arches used in churches and buildings are common examples of this application. Other examples include the exterior waterproof laminations in such structures as bridges and ships. Fai Ma Further Reading Bowyer, Jim L., Rubin Shmulsky, and John G. Hay- green. Forest Products and Wood Science: An Introduc- tion. 5th ed. Drawings by Karen Lilley. Ames, Iowa: Blackwell, 2007. Breyer, Donald E., et al. Design of Wood Structures. 6th ed. New York: McGraw-Hill, 2007. Diamant, R. M. E. Thermal and Acoustic Insulation. Bos- ton: Butterworths, 1986. Flynn, James H., Jr. A Guide to More Useful Woods of the World. Madison, Wis.: ForestProducts Society, 2007. Green, Harvey. Wood: Craft, Culture, History. New York: Viking, 2006. Hackett, Donald F., and Patrick E. Spielman. Modern Wood Technology. Milwaukee, Wis.: Bruce, 1968. Hoadley, R. Bruce. Understanding Wood: A Craftsman’s Guide to Wood Technology.Newtown, Conn.:Taunton Press, 2000. Panshin, A. J., and Carl de Zeeuw. Textbook of Wood Technology: Structure, Identification, Properties, and Uses of the Commercial Woods of the United States and Can- ada. 4th ed. New York: McGraw-Hill, 1980. U.S. Department of Agriculture, Forest Service, For- est Products Laboratory. The Encyclopedia of Wood. New York: Skyhorse, 2007. Walker, John C. F. Primary Wood Processing: Principles and Practice. 2d ed. Dordrecht, the Netherlands: Springer, 2006. See also: Forest management; Forest Service, U.S.; Forests; Paper; Renewable and nonrenewable resources; Timber industry; Wood and charcoal as fuel resources. World Bank Category: Organizations, agencies, and programs Date: Established 1945 The World Bank has played an active role in the development, use, and conservation of natural resources, such as forests and water, in developing countries. By providing financial and technical assistance, it aims to reduce global poverty by promoting better use of natural resources. It also helps developing countries adapt to the threat of climate change. Background The World Bank is also known as the International Bank for Reconstruction and Development. It was created after the Bretton Woods Conference in 1944. Its original goal was to rebuild international economic systems after World War II. Its focus shifted to helping developing countries with the stated goal of poverty reduction by offering financial, institutional, and technical support. Impact on Resource Use The World Bank suggests that poor countries have suffered from chronic poverty not because of a lack of natural resources but as a result of a “resource curse”— they lack the incentives to diversify their economies because of the abundance of natural resources. Poor management, inadequate infrastructure, and a lack Global Resources World Bank • 1359 of know-how are also cited as causes of poverty. Cli - mate change has posed further threats to developing countries, because poor people rely heavily on natural resources for their livelihoods. More episodes of flood and drought, owing to anthropologically in- duced climatic variability, will severely affect their survival. Because of this background, integrating natural resources into sustainable development has become the World Bank’s key strategy in rural development and environmental conservation. To achieve sustainable natural resources management, the World Bank focuses on four main areas: forests, desertification, water, and biodiversity. While many programs takeplace atthe community level, the World Bank also promotes crosscutting and cross- sectoral interventions at both national and international levels through public-private partnerships and civil society programs. The World Bank also intro- duces new technologies, such as biofuels, to help developing countries raise agricultural productivity and capitalize on the rising commodity price levels. In the 1980’s, the World Bank adopted the “Wash- ington Consensus” modelof developmentto privatize natural resources, suchas water.It argued that the state was too weak and too inefficient to manage water resources. Based on the theory defining water as an economic good and requiring users to pay for water, water is supplied, delivered, and privatized through market- based mechanisms and public-private partnerships. Such an approach to managing natural resources has caused controversies, however. Many poor people are denied access to clean water because they cannot af- ford it. Thepolicies ofderegulation andliberalization of markets are also blamed for neglecting issues such as equity and long-term ecological sustainability. Since the 1990’s, the WorldBank has promotedthe concept of “good governance.” It blames corruption and weak institutional support for the mismanage- ment of natural resources in developing countries. To combat corruption, it promotes transparency, ac- countability, and public participation. To strengthen capacity building, it forms organizations, such as water users, associations and village forestry committees, to manage resources. The World Bank is praised for acknowledging the role of power in managing natural resources, but it is criticized for offering a “one- size-fits-all” approach to institutional reforms and for overemphasizing economic growth over long-term re - source conservation. Sam Wong Web Site World Bank http://www.worldbank.org/ See also: Biofuels; Capitalism and resource exploita- tion; Desertification; Resource curse. World Commission on Environment and Development Category: Organizations, agencies, and programs Date: Established 1983 The United Nations World Commission on Environ- ment and Development, also known as the Brundtland Commission, issued a report in 1987 that popularized the concept of sustainable development: development that meets the needs of the present without depriving future generations of their ability to meet their own needs. Several subsequent global initiatives sprang from the commission’s work. Background With human populations and activities exerting un- precedented pressures on the environment, the United Nations General Assembly passed a resolution on December 19, 1983, establishing a special commission to examine the concerns of global environment and development to the year 2000 and beyond. This commission later took the name World Commission on Environment and Development (WCED). The WCED was also referred to as the Brundtland Com- mission for its chair, Gro Harlem Brundtland, who was Norway’s prime minister and former minister of the environment. Brundtland headed a commission of twenty-one other members. These commission- ers—government officials, environmental scientists, social scientists, and economists from developed and developing countries around the globe—served not as representatives oftheir respectivegovernments but as individual, independent experts. The WCED heldits firstofficial meetingin Geneva, Switzerland, in October, 1984. At this meeting the commission chose key issues for analysis, including population, energy, industry, food security, human settlements, international economic relationships, en - vironmental management, and international cooper - ation. 1360 • World Commission on Environment and Development Global Resources The WCED subsequently convened deliberative meetings around the world to gain an intimate understanding of regional environment and development concerns. It also held open public hearings in developed and developing countries where governmental representatives, researchers, experts, industrialists, nongovernmental agency representatives, and ordi- nary citizens could provide their insights and input. Impact on Resource Use In the spring of 1987, the WCEDpublished its final report, Our Common Future, commonly known as the Brundtland Report, which examined the political, so- cietal, and economic changes necessary to achieve sustainable development—that is, development that addresses present needs without sacrificing future generations’ abilities to address theirown. The report stresses the necessity of recognizing and managing the interrelation between environment and development instead of prioritizing one over the other. It calls for intensified and cooperative efforts among all nations to meet the needs of the poor, promote peace, enhance security, conserve and share resources, and assess environmental risk on a global basis. Though the WCED ceased its operations at the end of 1987, the following year, the Centre for Our Common Fu- ture was established in Geneva to promote the mes- sages of the WCED’s final report and to encourage di- alogue on sustainable development. Our Common Future and the work of the WCED laid the groundwork for the 1992 United Nations Confer- ence on Environment and Development, or Earth Summit, in Rio de Janeiro, Brazil. Sustainable development was a key concept underlying the agreements signed at the EarthSummit, includingthe Framework Convention on Climate Change; the Convention on Biological Diversity; the Rio Declaration on Environ- ment and Development; the Statement of Forest Prin- ciples; the resolution on desertification that later led to the United Nations Convention to Combat Deserti- fication; and Agenda 21, a plan for achieving sustainable development worldwide. Karen N. Kähler Web Site United Nations Documents Report of the World Commission on Environment and Development: Our Common Future http://www.un-documents.net/wced-ocf.htm See also: Agenda 21; Earth Summit; Sustainable de - velopment; United Nations climate change confer- ences; United Nations Convention to Combat Deser- tification; United Nations Framework Convention on Climate Change. World Conservation Union. See International Union for Conservation of Nature World Resources Institute Category: Organizations, agencies, and programs Date: Established 1982 The primary roles of the World Resources Institute are to find practical ways to protect the Earth and to make people’s lives better in the present and the future. It in- vestigates and analyzes global environmental and resource issues and their relationship with population growth and developmental issues that include deforestation, desertification, and global climate change. Background The World Resources Institute (WRI) was established on June 3, 1982, to address the need for research and practical solutions to help solve serious global environmental, resource, population, and development problems. The WRI held a global conference in1984 at which seventy-five experts and leaders in science, industry, government, energy, agriculture, and environmental studies from twenty countries established a list of practical proposals to assess and address global environmental and development problems and issues. In 1990, WRI conducted a feasibility study that laid the foundation for the creation of the Global Environ- ment Facility. Two years later, the WRI launched the Global Biodiversity Strategy, which was instrumental in the development of the Convention on Biological Diversity. Impact on Resource Use The WRI established four main goals to concentrate its efforts on the development and use of global re - Global Resources World Resources Institute • 1361 sources. The first goal is to protect the global climate system from further degradation from greenhouse gases and other hazardous emissions. The second goal is to keep the public informed about any deci- sions that affect natural resources and the environment. The third goal is to use businesses and markets to expand global economic opportunities, while protecting the environment. The fourth goal is to reverse the harmthat hasbeen done by deforestation, desertification, and global climate changes to ecosystems as much as possible, so that needed goods and services can be provided to people worldwide. The WRI is well knownfor its biennial publicationof the World Resources report, which provides an authori- tative assessment of the world’s natural resource base. Produced jointly with the United Nations Environ- ment Programme, the United Nations Development Program, and the World Bank, this report provides the latest information on the status of economic, population, natural resource, and global environmental conditions and trendsfor morethan 150 countries. In 2000, the WRI introduced its Global Forest Watch program, an online Web site devoted to monitoring forests worldwide. One year later it launched Earth- Trends, a Web site offering data and information about the environmental, social, and economic trends that help determine conditions in the world. Since 1985, the WRI has played a vital role in promoting effective global response to climate change. It has worked on international agreements and United States policies to protect climate systems worldwide. The WRI strongly advocates the reduction of greenhouse-gas emissions and encourages the development of clean energy alternatives that are sup- ported by businesses, governments, and the general public all over the world. In 2001, the WRI and the World Business Council for Sustainable Development played an instrumental role in the development of a global standard for measuring and reporting emissions of greenhouse gases, known as the Greenhouse Gas Protocol. The WRI provides, and helps other in- stitutions and governments provide, information and practical proposals for policy andinstitutional change that will help promote the wise, efficient use of global resources with minimal harm to the environment and in the best interests of people throughout the world. Alvin K. Benson Web Sites Global Forest Watch http://www.globalforestwatch.org/english/ index.htm World Resources Institute http://www.wri.org/ See also: Biodiversity; Ecology; United Nations Envi- ronment Programme; World Bank. World Wide Fund for Nature Categories: Organizations, agencies, and programs; social, economic, and political issues; environment, conservation, and resource management Date: Established September 11, 1961 One of the largest conservation organizations in the world, the World Wide Fund for Nature (formerly the World Wildlife Fund, and retaining that name in the United States) is dedicated to promoting theresponsible use of natural resources. Research campaigns and projects focus on creating preserves, ensuring survival of all species, protecting against damage, and encourag- ing a balance between humans, wildlife, and the environment. Background Established in 1961, the World Wide Fund for Nature (WWFN, formerly the World Wildlife Fund) was origi- nally the fund-raising arm of the International Union for Conservation of Nature (IUCN). The IUCN was founded in 1948 to conduct research and gather data identifying species in need of protection. In 1961, headquarters moved from France to Switzerland, and the two organizations worked in tandem on campaigns. A logo was created so the WWF would easily be identifiable. “Chi-chi,” a popular giant panda housed at the London Zoo, served as a model. The group’s first projects included saving the Arabian oryx from extinction, creating a footpath through a reserved section of forest in Madagascar, and transporting eight endangered white rhinoceroses from South Af- rica to Zimbabwe for breeding. The first major campaign, Operation Tiger, fo - cused on saving both tigers and their habitats. This in - 1362 • World Wide Fund for Nature Global Resources cluded a ban on tiger hunting in India, tagging and tracking remaining tigers to ensure their population increased, and creating havens for tigers in Indonesia, Thailand, India, and other parts of Asia. Smuggling and poaching of endangered animals and plants was next on the list. The WWf’s efforts to arrest these activities resulted in the Trade Records Analysis of Flora and Fauna in Commerce (TRAFFIC) in 1976. By 1980, the goals of the organization had broadened to address all aspects of nature and world resources, including all species (whether endangered or not), insects, flora, fauna, air, soil, freshwater supplies, oceans, and coastlines. This new focus warranted a change in name from the World Wildlife Fund to the World Wide Fund for Nature in 1986. The WWF and the black-and- white panda logo remain identifiers of theorgani- zation. In the United States, which has specific laws for fund-raising organizations, the WWF re- mains known as World Wildlife Fund-U.S. Impact on Resource Use As of 2009, the WWF network had funded eleven thousand projects and programs in 130 countries at a cost of nearly $1.17 billion. Key projects have included a moratorium on whale hunting, stop- ping the ivory trade, saving rhinoceroses, restoring orangutan habitats, and protecting mountain gorillas in Rwanda. Recent projects include establishing marine preserves; creating national parks in Colombia, Costa Rica, Nepal, and Bhutan; protecting the Amazon rain forest; establishingschool nature gardens in Zambia; andtraining local people to be wildlife scoutsto monitor species withdeclin- ing numbers. In 1992, the WWF teamedwith other organizations to educate and alert politicians and businesspeople about the environmental crisis during the Rio de Janeiro Earth Summit. The 1997 Living Planet Cam- paign educated people about the world’s biodiversity. It included Global 200, a framework of 238 terrestrial, marine, and freshwater ecoregions. International stan- dards for fisheries, established in 2000, help prevent overharvesting of seafood. During the 2009 global climate summit in Copenhagen, Demark, representatives of WWF attended forums on food security, water vulnerability, and the impact of climate change on major companies, lending WWF’s insights on these key issues. In recent decades, the focus has turned to sustainable use of resources, reducing pollution, correcting wasteful consumption of resources, and restoring dam- aged habitats orresources. For example, the WWF has worked with large corporations, such as Wal-Mart, on sustainable use of resources and agricultural issues. Lisa A. Wroble Web Site World Wide Fund for Nature http://www.worldwildlife.org/ See also: Conservation; Conservation biology; Earth Summit; Endangered species; Endangered Species Act; Global 200; International Union for Conserva - tion of Nature. Global Resources World Wide Fund for Nature • 1363 Activists from the World Wide Fund for Nature (also known as the World Wildlife Fund) gather in front of the Angel of Independence monument in Mexico City in 2006. (Henry Romero/Reuters/Landov) Z Zeolites Category: Mineral and other nonliving resources Where Found Zeolites are found naturally wherever volcanic rock and ash interact with alkaline groundwater. They are mined extensively in many parts of the world. Zeolites are also easily produced through artificial means; often artificial zeolites are purer andtherefore prefer- able to the organic variety. As of 2008, 175 cataloged unique zeolite frameworks had been identified, 40 of which are naturally occurring. Primary Uses The primary use for zeolites is in laundry detergents. The mineral’s porous nature allows particles of dirt and contaminants to be captured in the wash cycle and then rinsed away in the rinse cycle. Other common uses are as aquariumfilters andcat litter. Zeolites are also used extensively within the medical profes- sion as molecular sieves to filter and purify air to make medical grade oxygen. Technical Definition Zeolite is a crystalline mineral most commonly used as an absorbent in commercial settings. Zeolites are microporous aluminosilicates with well-defined structures that act as “molecular sieves,” capturing oxygen, minerals, and water and holding them within their many and variable-sized pores. Zeolites generally contain silicon, aluminum, andoxygen in theirframe and water or other molecules within their pores. Their defining feature is a framework made up of four connected networks of atoms. They are tetrahedrous in nature, with a silicon atom in the middle and oxygen atoms in the corners. They can link together by their corners and form beautiful structures that contain cavities and channels in which other molecules can become trapped. Because of this property, Zeolites are excellent means of filtering out impurities in many things. Description, Distribution, and Forms Zeolites are aluminosilicates. They are more commonly referred to as “molecular sieves” because of a particular ability within the substance to sort molecules by their sizes and shapes. The size of a pore within the zeolite controls what molecules can flow into it. Thesepores are generally noncylindricalin nature. An “eight-ring” refers to a closed loop consisting of eight silicon or aluminum atoms and eight oxygen atoms. These atoms are tetrahedral in nature but not always symmetrical because of the bonding re- straints within the zeolite, which are often often based on the positioning of the oxygen atoms within the structure. Zeolite products are many and varied. Found in both natural and human-made forms, they are capable of absorbing and filtering out impurities in water and other liquids. They are resistant to heat and chemicals, which makes them excellent filtration devices in nuclear reactors and oil filtration systems. History Zeolite was given its name by Swedish mineralo- gist Axel Fredrik Cronstedt. Cronstedt heated a material then referred to as stilbite and observed that a small piece of the substance produced a large amount of steam. Cronstedt, pulling from Zeolites are known for their high absorbency. (USGS) the Greek words zeo, which means “boil,” and lithos, which means “stone,” named the material zeolite. Obtaining Zeolites Zeolites are formed when volcanic rock and layers of ash are subjectedto groundwater containing alkaline. These types of zeolites are seldom pure, often containing contaminates from other minerals and substances. Open-pit zeolite mines can be found in Ar- kansas, Idaho, and New Mexico. Topsoil is removed from the site, making access to the zeolite possible. The zeolite can be blasted free, cut free with ripper blades, or scraped from the ground with a bulldozer or top loader. Once removed from the ground, the zeolite is crushed, dried, and milled. Once processed, the substance is ready to use. Uses of Zeolites Zeolites can be foundin many places.Their adaptabil- ity as a natural and human-made filter makes them useful in both household and industrial settings. Oxygen concentrators containing zeolite are commonly used to produce medical-grade oxygen. The zeolite is able to filter impurities out of the air. Zeo- lites are also commonly used in water filtration systems for the same reason; they capture impurities in the water when water is filtered through them. Zeolites are resistant to radiation, making them quite useful in nuclear reactions. They capture debris and waste products inside nuclear reactors. These waste products can be removed easily and disposed of without inhibiting the reactor’s capabilities. Once filled with fission by-products, the zeolite can be hard- pressed. This seals in the fission waste, making the by- product more easily disposable than the by-products of more conventional radioactive waste disposal methods. In agriculture, a naturally occurring zeolite called clinoptilolite is usedin thetreatment of soil.The absorbent nature of this particular zeolite allows for vital minerals to be time-released into the soil. Potassium and nitrogen, in particular, are substances that can be released in this manner. Also, because zeolites are absorbent, water can be introduced into arid soil. In regions where water is overly abundant in the soil, intro- ducing zeolites can help prevent root rot and improve harvests. Zeolites introduced into waterlogged soil can capture and retain up to 55 percent of their weight. Zeolites are also commonly used inthe heating and refrigerating industry. Zeolite’s ability to absorb heat makes it useful in the capture and collection of heat and moisture that would escape otherwise. The intro- duction of zeolite into such environments improves the efficiency of both tasks. This ability of zeolites to capture impurities in water and other liquids is not overlooked in the pet supply industry. Zeolite is an ingredient in many aquarium filters. It captures and filters ammonia and other nitrogenous compounds in aquariums, keeping the water from becoming toxic to fish and other aquatic creatures. Another common use for zeolites is in cat litter. The nonclumping variety of cat litter is commonly made of zeolite or diatomite. This porous litter cap- turesliquid, andis easily removed from the litter box. Zeolites introduced into the foodsupply of animals can improve the animal’s ability to process the food and help to improve the animal’s bone density. Addi- tionally, zeolites can reduce the airborne ammonia in holding pens by up to 80 percent. Zeolite is also used in the petrochemical industry, filtering out impurities in crude oil and other petroleum products. Zeolite is hydrogenized and turned into powerful acid via ion exchange. Once zeolite is acidified, processes such as isomerization (a process that converts one compound into another with the same number of atoms, only rearranged), alkylation (which transfers the alkyle group of one atom to another), and catalytic cracking can be carried out. Cat- alytic cracking is a process that requires a furnace and a reactor. Crude oil is heated in the furnace, then sent to the reactor, where it is introduced to the acidic zeolite. It is run through the zeolite three times; each time it is filtered through a cooler version of the acidified zeolite. The next step is the separation of hydro- gen from the crude oil. It is sent to a fractionator (yet another separation process that divides components of a compound by their physical qualities) in the final step and becomes the end product. Roger Dale Trexler Further Reading Auerbach, Scott M., Kathleen A. Carrado, and Prabir K. Dutta. Handbook of Zeolite Science and Technology. Boca Raton, Fla.: CRC Press, 2003. Peiper, Howard. Zeolite: Nature’s Heavy Metal Detoxifier. Sheffield, Mass.: Safe Goods, 2006. Xu, Ruren, et al. Chemistry of Zeolites and Related Porous Materials: Synthesis and Structure. New York: Wiley- Interscience, 2007. Global Resources Zeolites • 1365 . poverty not because of a lack of natural resources but as a result of a “resource curse”— they lack the incentives to diversify their economies because of the abundance of natural resources. Poor management,. concentrate its efforts on the development and use of global re - Global Resources World Resources Institute • 1361 sources. The first goal is to protect the global climate system from further degradation. efficient use of global resources with minimal harm to the environment and in the best interests of people throughout the world. Alvin K. Benson Web Sites Global Forest Watch http://www.globalforestwatch.org/english/ index.htm World