Encyclopedia of Global Resources part 48 pptx

Primary Uses Ferroalloys are used extensively in the iron and steel industry.. More than 99 percent of ferronickel use within the United States is for stainless steel and heat-resistant

418 • Feldspars Global Resources

Million Metric Tons

Source:Data from the U.S Geological Survey,Mineral Commodity Summaries, 2009 U.S Government Printing Office, 2009.

Argentina

Brazil

China

Colombia

Czech Republic

Egypt

France

Germany

India

Iran

Italy

Japan

Malaysia

Mexico

Poland

Portugal

South Korea

Spain

Thailand

Turkey

United States

Venezuela

Other countries

290,000 130,000

2,000,000 100,000

490,000 350,000

170,000 160,000 260,000

4,200,000

250,000

350,000 130,000 400,000 600,000

3,800,000

200,000

650,000

700,000

440,000

800,000

600,000

1,200,000

Feldspar: World Mine Production, 2008

icut, to grind feldspar for the newly developed pottery

industry in the United States

The largest production of feldspar in the United

States is in North Carolina, followed by Virginia,

Cali-fornia, Oklahoma, Georgia, Idaho, and South Dakota

Crude feldspar is also produced by at least thirty-eight

other countries China, Turkey, Italy, and Thailand

jointly produce approximately 60 percent of the

world’s total feldspar U.S production of crude

feld-spar is about 3 percent of the world total

Obtaining Feldspar

The method used to obtain feldspar depends on

the type of deposit to be mined Most feldspar can

be quarried by open-pit mining Some feldspars are

mined by boring down through distinct zones within

pegmatite dikes, but many deposits require the use of

explosives and drills Dragline excavators are used to

mine feldspathic sands High-grade feldspar can be

dry-processed It is sent through jaw crushers, rolls,

and oiled pebble mills, and is finally subjected to

high-intensity magnetic or electrostatic treatments that

re-duce the iron content to acceptable levels

Feldspathic sands are crushed and rolled, then

processed by a three-step froth flotation sequence

that removes mica, extracts the iron-bearing miner-als, and finally separates the quartz residuals Some-times the last flotation procedure is omitted so that

a feldspar-quartz mixture can be sold to the glass-making industry The feldspar is ground to about twenty mesh for glassmaking and to two hundred mesh or finer for ceramic and filler applications

Uses of Feldspar Feldspar is used in the manufacturing of soaps, glass, enamels, and pottery As a scouring soap, its interme-diate hardness, angular fracture, and two directions

of cleavage cause it to form sharp-edged, gritty parti-cles that are hard enough to abrade but soft enough not to cause damage to surfaces In glassmaking, feld-spar brings alumina, together with alkalies, into the melt This enhances the workability of the glass for shaping and gives it better chemical stability

Feldspar is used primarily as a flux in ceramics mix-tures to make vitreous china and porcelain enamels The feldspar is ground to a very fine state and mixed with kaolin or clay and quartz The feldspar fuses at a temperature below most of the other components and acts as a vitreous binder, cementing the material together Fused feldspar is also used as the major part

of the glaze on porcelain ware

Dion C Stewart

Further Reading

Chatterjee, Kaulir Kisor “Feldspar.” In Uses of

Indus-trial Minerals, Rocks, and Freshwater New York: Nova

Science, 2009

Deer, W A., R A Howie, and J Zussman Framework

Silcates: Feldspars Vol 4A in Rock-Forming Minerals.

2d ed London: Geological Society, 2001

Klein, Cornelis, and Barbara Dutrow The Twenty-third

Edition of the Manual of Mineral Science 23d ed.

Hoboken, N.J.: J Wiley, 2008

Kogel, Jessica Elzea, et al., eds “Feldspars.” In

Indus-trial Minerals and Rocks: Commodities, Markets, and Uses 7th ed Littleton, Colo.: Society for Mining,

Metallurgy, and Exploration, 2006

Ribbe, R H., ed Feldspar Mineralogy 2d ed

Washing-ton, D.C.: Mineralogical Society of America, 1983

Smith, Joseph V., and William L Brown Feldspar

Min-erals 2d rev and extended ed New York: Springer,

1988

Wenk, Hans-Rudolf, and Andrei Bulakh Minerals:

Their Constitution and Origin New York: Cambridge

University Press, 2004

Commodity Summaries, 2009

Data from the U.S Geological Survey,

U.S Government Printing Office, 2009.

Glass 65%

Pottery

and other

35%

U.S End Uses of Feldspar

Web Sites

U.S Geological Survey

Feldspar

http://minerals.er.usgs.gov/minerals/pubs/

commodity/gemstones/sp14-95/feldspar.html

U.S Geological Survey

Feldspar: Statistics and Information

http://minerals.usgs.gov/minerals/pubs/

commodity/feldspar

See also: Abrasives; Ceramics; China; France;

Igne-ous processes, rocks, and mineral deposits; Italy;

Mex-ico; Pegmatites; Plutonic rocks and mineral deposits;

Spain; Thailand; Turkey; United States

Fermi, Enrico

Category: People

Born: September 29, 1901; Rome, Italy

Died: November 28, 1954; Chicago, Illinois

Fermi was an Italian physicist known for his work on

the first nuclear reactor and his theory of beta decay.

He contributed to quantum theory, statistical

mechan-ics, and nuclear and particle physics He conducted

investigations on the atom’s nucleus and

experi-mented with uranium, which led to his observation

of nuclear fission His discovery of a methodology to

release nuclear energy earned him the Nobel Prize in

Physics in 1938.

Biographical Background

Enrico Fermi was born in Rome, Italy, the son of a

railroad official and a schoolteacher He excelled

in school, sharing his interests with his older

brother, Giulio, who died in 1915 after minor

throat surgery After high school, Fermi studied

at the University of Pisa from 1918 to 1922,

com-pleting his undergraduate degree and Ph.D in

physics Fermi solved the Fourier analysis for his

college entrance exam and published his first

sci-entific work on electrical charges in transient

conditions in 1921

Fermi received a fellowship to work at the

Uni-versity of Göttingen in Germany in 1924 He

taught math at the University of Rome and the

University of Florence, where he researched what

would later be called the Fermi-Dirac statistics Fermi studied at Leyden in the Netherlands and married Laura Capon in 1928 Their daughter, Nella Fermi Weiner (1931-1995), and son, Giulio (1936-1997), both obtained Ph.D.’s Fermi was one of the only phys-icists of the twentieth century to excel in both theoret-ical and applied nuclear physics He died from stom-ach cancer, resulting from radiation exposure, on November 28, 1954

After his death, his lecture notes were transcribed into books, and schools and many awards were named

in his honor Three nuclear reactor installations were named after him, as was “fermium,” the one hun-dredth element on the periodic table

Impact on Resource Use Fermi’s research at the University of Rome led to the discovery of uranium fission in 1934 In 1939, on the Columbia University campus, the first splitting of the uranium atom took place Fermi’s focus was on

Enrico Fermi’s work with radioactive isotopes led to the development of the atomic bomb (NARA)

the isotope separation phase of the atomic energy

project In 1942, he led a famous team of scientists

in lighting the first atomic fire on earth at the

Univer-sity of Chicago His studies led to the construction of

the first nuclear pile, called Chicago Pile-1, whereby

he assessed the properties of fission, the key to

extract-ing energy from nuclear reactions

Another example of his impact was noted on July

16, 1945, when Fermi supervised the design and

as-sembly of the atomic bomb Fermi dropped small

pieces of paper as the wave of the blast reached him

and then measured the distance those pieces were

blown This allowed him to estimate the bomb’s

en-ergy yield The calculations became known as the

“Fermi method.” His discovery of how to release

nu-clear energy encouraged the development of many

peaceful uses for nuclear energy

Fermi discovered induced radioactivity

(radioac-tive elements produced by the irradiation of

neu-trons) and nonexplosive uranium, which is

trans-muted into plutonium (a vital element in the atomic

and hydrogen bombs and the first atomic

subma-rine) His research led to the creation of more than

forty artificial radioactive isotopes, and his theory of

neutron decay became the model for future theories

of particle interaction

Gina M Robertiello

See also: Hydrogen; Nobel, Alfred; Nuclear energy;

Nuclear Energy Institute; Uranium

Ferroalloys

Category: Mineral and other nonliving resources

Where Found

Ferroalloy production occurs in many countries

around the world, but the primary

ferroalloy-produc-ing countries are China, South Africa, Ukraine, Russia,

and Kazakhstan These five countries produce more

than 74 percent of the world’s ferroalloy supply

How-ever, because the various ferroalloys contain a

num-ber of different elements, many parts of the world

sup-ply minerals important in ferroalloy production

Primary Uses

Ferroalloys are used extensively in the iron and steel

industry The type of alloy produced depends upon

the properties of the element that is added to the iron Stainless steel, high-strength steels, tool steels, and cast irons are the major ferroalloy products Some ferroalloys are also used to produce metal coatings, catalysts, electrodes, lighting filaments, aerospace and marine products, medical implants, and household batteries

Technical Definition Ferroalloys constitute a wide variety of alloyed metals that combine a large percentage of iron with a smaller percentage of one or more elements Combining other elements with iron imparts superior strength

to these alloys, and this increased strength enables the metals to be used in many important products within the metallurgical industry Ferroalloys have lower melting points than do the pure elements that form them; therefore, they are incorporated more easily into molten metal Manganese, chromium, magne-sium, molybdenum, nickel, titanium, vanadium, sili-con, cobalt, copper, boron, phosphorus, niobium, tungsten, aluminum, and zirconium are the primary elements mixed in varying proportions with iron to produce ferroalloys Ferroalloys are produced pri-marily in electric arc furnaces; the nonferrous metal combines with the iron at high temperatures to pro-duce the various types of steel

Description, Distribution, and Forms Much of the stainless-steel production of Europe, Asia, and North and South America is possible because of ferrochromium In 2007, approximately 29 metric tons

of stainless steel were produced throughout the world Most chromite ore mining takes place in China, India, South Africa, Russia, Turkey, and Kazakhstan The ma-jority of chromite ore is smelted in electric arc furnaces

to produce ferrochromium, which is then exported to the countries that manufacture stainless steel Ferromanganese and silicomanganese are primary ingredients in steelmaking Most of the U.S supply of these alloys is imported from South Africa, although China, Brazil, India, and Ukraine are also important producers The United States also produces some ferromanganese at a plant near Marietta, Ohio Be-sides being a key component in steel manufacturing, manganese is used in the production of household batteries Silicomanganese production at plants in New Haven, West Virginia, the United Kingdom, and Ukraine has been vital to steelmaking for a number of years

Ferrosilicon is a deoxidizing agent in cast iron and

steel production China, Brazil, and Russia are the

main producers of ferrosilicon, with China producing

more than four times as much as the other two

coun-tries

More than 99 percent of ferronickel use within the

United States is for stainless steel and heat-resistant

steel Stainless-steel cooking pots, pans, and kitchen

sinks are products of the ferronickel industry The

United States does not produce any primary nickel

but instead produces a remelt alloy with small

per-centages of chromium and nickel from recycled

mate-rials Japan, New Caledonia, Colombia, Greece,

Ukraine, Indonesia, the Dominican Republic, and

Venezuela lead the world in ferronickel production

Another major ferroalloy is ferromolybdenum, a

component of stainless steels, tool steels, and cast

iron About 80 percent of world production of

ferro-molybdenum takes place in Chile, China, and the

United States, while the remainder occurs in Canada,

Mexico, and Peru

Ferrotitanium plays a large role in the steel

indus-try as a deoxidizing and stabilizing agent as well as an

alloy that assists in controlling the grain size of steel

Titanium is not naturally found in metallic form but

instead is mined from titanates, oxides, and

silico-titanites Ferrotitanium is then produced by an

in-duction melting process Steels with a high titanium

content include stainless, high-strength, and

intersti-tial-free (space-free) forms Other important

ferroti-tanium uses include catalysts, pigments, floor

cover-ings, roofing material, aerospace products, medical

implants, armor, and marine industrial goods Major

producers of ferrotitanium include China, India,

Ja-pan, Russia, the United Kingdom, and the United

States

Ferrovanadium, used in the manufacture of

cata-lysts and chemicals, is produced in the United States

mostly from petroleum ash and residues as well as

from tar sands China and South Africa contribute 71

percent of the world’s supply of ferrovanadium, while

Russia makes up most of the remaining supply

History

Steel has been produced by a number of methods

since before the fifteenth century, but only since

the seventeenth century has it been produced

effi-ciently The Bessemer process, invented in the

mid-1800’s by Sir Henry Bessemer, enabled steel to be

mass-produced in a cost-effective manner

Improve-ments on the Bessemer process included the Thomas-Gilchrist process and the Siemens-Martin process of open-hearth steel manufacture Basic oxygen steel-making, also known as the Linz-Donawitz process, was developed in the 1950’s, and although the Bessemer process and other processes continued to be used for

a few more years, basic oxygen steelmaking soon became the process of choice for modern steel manu-facture

Creating Ferroalloys Ferroalloys have been used in the steel manufactur-ing industry primarily since the 1960’s In the twenti-eth century, metallurgists discovered that adding vary-ing amounts of manganese, silicon, or aluminum to the molten steel pulled oxygen away from the melted material, thus allowing for sound castings without bubbles or blowholes The other ferroalloys—those containing chromium, tungsten, molybdenum, vana-dium, titanium, and boron—provide a method for making specialty steels other than ordinary carbon steel By adding small amounts of the other metals, high-strength, heat-resistant steels, such as stainless steel, can be produced

The amount of steel that a country produces is often considered to be an important indicator of eco-nomic progress Therefore, the production of ferro-alloys within the iron and steel manufacturing indus-try is also a key factor of the economy of the countries

in which it takes place In the twenty-first century, the economic booms in China and India brought about a large increase in demand for steel products and a cor-responding need for a large number of workers in this industry The top producers of steel in the world are,

in order of metric-ton production per year, China, Ja-pan, Russia, and the United States Each of these countries has many thousands of workers in its steel industry and in the mining industries, which supply the raw materials for iron and steel production

Uses of Ferroalloys The primary use of ferroalloys is in the manufactur-ing of iron and steel Combinmanufactur-ing various metallic ele-ments with iron results in a strong, stable product vital

to many industries Stainless and heat-resisting steels are produced from ferrochromium, ferrotitanium, and ferronickel Ordinary carbon steel rusts, but stainless steel resists corrosion because of the chro-mium oxide film it contains In general, at least 11 percent chromium must be added to the steel in

der to produce the stainless quality Up to 26 percent

chromium must be added if the stainless steel is to be

exposed to harsh environmental conditions

Al-though stainless steel has a huge number of

applica-tions in modern society, it is mostly used for cutlery,

appliances, surgical instruments, cooking

equip-ment, and aerospace parts Because stainless steel is

also resistant to bacterial growth, it is important in the

cooking and medical industries Stainless steel is also

used in jewelry and firearm production

Ferrochromium is used in the chemical industry as

a surface treatment coating for metals Besides the

primary uses of ferroalloys in steelmaking, these

sub-stances are also used to produce catalysts in catalytic

converters, pigments in paint, grinding and cutting

tools, lighting filaments, and electrodes Ferrosilicon

is used by the military to produce hydrogen for

bal-loons in a process that combines sodium hydroxide,

ferrosilicon, and water

Lenela Glass-Godwin

Further Reading

Corathers, Lisa A “Manganese.” USGS Minerals

Year-book (2007).

Dunkley, J J., and D Norval “Atomisation of

Ferro-alloys.” In Industrial Minerals and Rocks, edited by

Jessica Elzea Kogel 6th ed Littleton, Colo.: Society

of Mining, Metallurgy, and Exploration, 2004

Jones, Andrew “The Market and Cost Environments

for Bulk Ferroalloys.” In International Conference on

Innovations in the Ferroalloy Industry New Delhi: The

Indian Ferro Alloy Producers’ Association, 2004

Papp, J F “Chromite.” In Industrial Minerals and Rocks,

edited by Jessica Elzea Kogel 6th ed Littleton,

Colo.: Society of Mining, Metallurgy, and

Explora-tion, 2004

Web Site

U.S Geological Survey

Minerals Information: Ferroalloys Statistics and

Information

http://minerals.usgs.gov/minerals/pubs/

commodity/ferroalloys/

See also: Aluminum; Bessemer process; Boron;

Chromium; Cobalt; Copper; Magnesium; Manganese;

Molybdenum; Nickel; Niobium; Siemens, William;

Silicon; Steel; Steel industry; Titanium; Tungsten;

Va-nadium; Zirconium

Fertilizers

Categories: Plant and animal resources; products from resources

Fertilizers, those materials that are used to modify the chemical composition of the soil in order to enhance plant growth, represent an important use of natural resources because agricultural systems are dependent upon the ability to retain soil fertility Among the essen-tial nutrients provided in fertilizers are calcium, mag-nesium, sulfur, nitrogen, potassium, and phosphorus.

Background

It has been said that civilization owes its existence to the 15-centimeter layer of soil covering the Earth’s landmasses This layer of topsoil represents the root zone for the majority of the world’s food and fiber crops Soil is a dynamic, chemically reactive medium, and agricultural soils must provide structural support for plants, contain a sufficient supply of plant nutri-ents, and exhibit an adequate capacity to hold and ex-change minerals As plants grow and develop, they re-move the essential mineral nutrients from the soil Since normal crop production usually requires the re-moval of plants or plant parts, nutrients are continu-ously being removed from the soil Therefore, the long-term agricultural utilization of any soil requires periodic fertilization to replace these lost nutrients Fertilizers are associated with every aspect of this nu-trient replacement process The application of fertil-izer is based on a knowledge of plant growth and de-velopment, soil chemistry, and plant-soil interactions

Soil Nutrients Plants require an adequate supply of both macro-nutrients (calcium, magnesium, sulfur, nitrogen, po-tassium, and phosphorus) and micronutrients (iron, copper, zinc, boron, manganese, chloride, and mo-lybdenum) from the soil If any one of these nutrients

is not present in sufficient amounts, plant growth and, ultimately, yields will be reduced Because micronutri-ents are required in small quantities and deficiencies

in these minerals occur infrequently, the majority of agricultural fertilizers contain only macronutrients Although magnesium and calcium are utilized in large quantities, most agricultural soils contain an abundance of these two elements, either derived from parent material or added as lime Most soils also

tain sufficient amounts of sulfur from the weathering

of sulfur-containing minerals, the presence of sulfur

in other fertilizers, and atmospheric pollutants

The remaining three macronutrients (nitrogen,

potassium, and phosphorus) are readily depleted and

are referred to as fertilizer elements Hence, these

ele-ments must be added to most soils on a regular basis

Fertilizers containing two or more nutrients are called

mixed fertilizers A fertilizer labeled 10-10-10, for

example, means that the product contains 10 percent

nitrogen, 10 percent phosphorus, and 10 percent

po-tassium Since these elements can be supplied in a

number of different forms, some of which may not be

immediately useful to plants, most states require that

the label reflect the percentage of nutrients available

for plant utilization Fertilizers are produced in a wide

variety of single and mixed formulations, and the

per-centage of available nutrients generally ranges from a

low of 5 percent to a high of 33 percent Mixed

fertiliz-ers may also contain varying amounts of different

micronutrients

Fertilizer Production

Nitrogen fertilizers can be classified as either

chemi-cal or natural organic Natural organic sources are

de-rived from plant and animal residues and include

such materials as animal manures, cottonseed meal,

and soybean meal Since natural organic fertilizers

contain relatively small amounts of nitrogen,

com-mercial operations rely on chemical fertilizers

de-rived from sources other than plants and animals The

major chemical sources of nitrogen include both

am-monium compounds and nitrates The chemical

fixa-tion of atmospheric nitrogen by the Claude-Haber

ammonification process is the cornerstone of the

modern nitrogen fertilizer manufacturing process

Once the ammonia is produced, it can be applied

di-rectly to the soil as anhydrous ammonia, or it can be

mixed with water and supplied as a solution of

aque-ous ammonia and used in chemical reactions to

pro-duce other ammonium fertilizers or urea, or

con-verted to nitrates that can be used to make nitrate

fertilizers

Some organic fertilizers contain small amounts

of phosphorus, and organically derived phosphates

from guano or acid-treated bonemeal were used in the

past However, the supply of these materials is scarce

Almost all commercially produced agricultural

phos-phates are applied as either phosphoric acid or

super-phosphate derived from rock super-phosphate The major

phosphate component in commercially important deposits of rock phosphate is apatite The apatite

is mined, processed to separate the phosphorus-containing fraction from inert materials, and then treated with sulfuric acid to break the apatite bond The superphosphate precipitates out of the solution and sets up as a hard block, which can be mechani-cally granulated to produce a fertilizer containing cal-cium, sulfur, and phosphorus Potassium fertilizers, commonly called “potash,” are also obtained from mineral deposits below the Earth’s surface The major commercially available potassium fertilizers are potas-sium chloride extracted from sylvanite ore, potaspotas-sium sulfate produced by various methods (including ex-traction from langbeinite or burkeite ores or chemi-cal reactions with potassium chloride), and potassium nitrate, which can be manufactured by several differ-ent chemical processes Although limited, there are sources of organic potassium fertilizers such as to-bacco stalks and dried kelp

While the individual nitrogen, phosphorus, and potassium fertilizers can be applied directly to the soil, they are also commonly used to manufacture mixed fertilizers From two to ten different materials with widely different properties are mixed together in the manufacturing process The three most common processes utilized in mixed fertilizer production are the ammonification of phosphorus materials and the subsequent addition of other materials, bulk blend-ing of solid blend-ingredients, and liquid mixblend-ing Fillers and make-weight materials are often added to make up the difference between the weight of fertilizer materi-als required to furnish the stated amount of nutrient and the desired bulk of mixed products Mixed fertil-izers have the obvious advantage of supplying all the required nutrients in one application

Benefits and Costs For every crop there is a point at which the yield may continue to increase with application of additional nutrients, but the increase will not offset the addi-tional cost of the fertilizer Therefore, considerable care should be exercised when applying fertilizer The economically feasible practice, therefore, is to apply the appropriate amount of fertilizer to produce maxi-mum profit rather than maximaxi-mum yield Moreover, since excessive fertilization can result in adverse soil reactions that damage plant roots or produce unde-sired growth patterns, overfertilization can actually decrease yields If supplied in excessive amounts, some

of the micronutrients are toxic to plants and will

dra-matically reduce plant growth Fertilizer

manufactur-ers must ensure that their products contain the

speci-fied amounts of nutrients indicated on their labels

and that there are no contaminants that could

ad-versely affect plant yield directly or indirectly through

undesirable soil reactions

The environment can also be adversely affect by

overfertilization Excess nutrients can be leached

through the soil into underground water supplies

and/or removed from the soil in the runoff water that

eventually empties into streams and lakes High levels

of plant nutrients in streams and lakes

(eutrophica-tion) can result in abnormal algal growth, which can

cause serious pollution problems Water that contains

excessive amounts of plant nutrients can also pose

health problems if it is consumed by humans or

live-stock

Importance to Food Production

Without a doubt, the modern use of fertilizer has

dramatically increased crop yields If food and fiber

production is to keep pace with the world’s growing

population, increased reliance on fertilizers will be

re-quired in the future With ever-increasing attention to

the environment, future research will primarily be

aimed at finding fertilizer materials that will remain in

the field to which they are applied and at improving

application and cultivation techniques to contain

ma-terials within the designated application area The use

of technology developed from discoveries in the field

of molecular biology to develop more efficient plants

holds considerable promise for the future

D R Gossett

Further Reading

Altieri, Miguel A Agroecology: The Scientific Basis of

Alter-native Agriculture Boulder, Colo.: Westview Press,

1987

Black, C A Soil-Plant Relationships 2d ed Malabar,

Fla.: R E Krieger, 1984

Brady, Nyle C., and Ray R Weil The Nature and

Prop-erties of Soils 14th ed Upper Saddle River, N.J.:

Prentice Hall, 2008

Elsworth, Langdon R., and Walter O Paley, eds

Fertil-izers: Properties, Applications, and Effects New York:

Nova Science, 2008

Engelstad, Orvis P Fertilizer Technology and Use 3d ed.

Madison, Wis.: Soil Science Society of America,

1986

Follett, Roy H., Larry S Murphy, and Roy L Donahue

Fertilizers and Soil Amendments Englewood Cliffs,

N.J.: Prentice-Hall, 1981

Hall, William L., Jr., and Wayne P Robarge, eds

Envi-ronmental Impact of Fertilizer on Soil and Water

Wash-ington, D.C.: American Chemical Society, 2004 Havlin, John L., Samuel Tisdale, Werner Nelson, and

James D Beaton Soil Fertility and Fertilizers: An

Intro-duction to Nutrient Management 7th ed Upper

Sad-dle River, N.J.: Pearson Prentice Hall, 2005

Web Sites Agriculture and Agri-Food Canada Manure, Fertilizer, and Pesticide Management in Canada

http://www4.agr.gc.ca/AAFC-AAC/display-afficher.do?id=1178825328101&lang=eng Economic Research Service, U.S Department of Agriculture

U.S Fertilizer Use and Price http://www.ers.usda.gov/Data/FertilizerUse See also: Agriculture industr y; Eutrophication; Green Revolution; Guano; Horticulture; Hydropon-ics; Monoculture agriculture; Nitrogen and ammo-nia; Potash; Slash-and-burn agriculture; Soil degrada-tion

Fiberglass

Category: Products from resources

Fiberglass has many practical uses, especially in struc-tural applications and insulation, because its fibers are stronger than steel and will not burn, stretch, rot,

or fade.

Definition Fiberglass consists of fine, flexible glass filaments or fi-bers drawn or blown directly from a glass melt These fibers may be many times finer than human hair

Overview Fiberglass is typically made in a two-stage process Glass is first melted and formed into marbles in an electric furnace, and then fibers are drawn continu-ously through holes in a platinum bushing and wound

onto a revolving drum like threads on spools The

drum can pull out more than 3 kilometers of fibers in

a minute, and up to 153 kilometers of fiber can be

drawn from one glass marble that is 1.6 centimeters in

diameter For a given set of operating conditions, the

size of the fibers is uniform, with diameters varying

from approximately 0.00025 centimeter to 0.00125

centimeter, depending on the application Some

ultrafine fibers have diameters of 0.0000762

centime-ter or less A typical composition of fiberglass (E glass)

is 54 percent silica, 15 percent alumina, 16 percent

calcia, 9.5 percent boron oxide, 5 percent magnesia,

and 0.5 percent sodium oxide by weight Because of

its low alkali (sodium) content, this type of fiberglass

has good durability and strength, and because of the

boron, it can be melted at reasonably low

tempera-tures

Coarse glass fibers were used by the ancient

Egyp-tians to decorate dishes, cups, bottles, and vases At

the Columbian Exposition in Chicago in 1893,

Ed-ward Drummond Libbey exhibited a dress made of

fiberglass and silk During World War I (1914-1918),

the Germans produced fiberglass in small diameters

as a substitute for asbestos In 1938, the

Owens-Corning Fiberglass Corporation was formed in the

United States, and fiberglass production was soon

started on a commercial scale

Fiberglass wool, made of loosely intertwined strands

of glass with air pockets in between, is an excellent

sulator against heat and cold It is used as a thermal

in-sulator in the exterior walls and ceilings of homes and

other buildings, as a thermal and electrical insulator

in furnaces, ovens, water heaters, refrigerators, and

freezers, and as a thermal and sound insulator in

air-planes Fiberglass is commonly combined with plastic

polymers to produce laminates that can be formed

into complex shapes for use in automobile and truck

bodies, boats, carport roofs, swimming pool covers,

and other items requiring light weight, strength, and

corrosion resistance In addition, fiberglass is woven

into a variety of fabrics, tapes, braids, and cords for use

in shower curtains, fireproof draperies, and electrical

insulation of wire and cable in electric motors,

gener-ators, transformers, meters, and electronic

equip-ment

Alvin K Benson

See also: Aluminum; Boron; Glass; Petrochemical

products; Sedimentary processes, rocks, and mineral

deposits; Silicates; Silicon; Textiles and fabrics

Fires

Category: Environment, conservation, and resource management

Wildfire is an integral part of wilderness life cycles, helping keep ecosystems healthy and diverse in plant and animal life Controlled human-set fires aid farm-ers, ranchfarm-ers, and foresters in making their lands more productive.

Background Fire is both inevitable and necessary to most land eco-systems Every day, lightning strikes the ground about eight million times globally, and one stroke in twenty-five can start a fire Even so, lightning accounts for only about 10 percent of ignitions; humans are the leading agent in setting fires Fire was one of the first tools humans used to shape their environment, and it has remained among the most common tools ever since Add to lightning and humans as agents the mol-ten rock from volcanoes and the sparks sometimes caused by rock slides, and not surprisingly millions

of hectares of land burn worldwide every year Because fire is so prevalent, ecosystems have evolved tolerance to it or even a symbiotic dependence on it Wildfires foster decomposition of dead material, recy-cle nutrients, control diseases by burning infected plants and trees, help determine which plant species flourish in a particular area, and in some cases even play a role in germinating seeds Purposefully set fires, today called controlled burns, have flushed game for hunters since prehistoric times and are still put to work fertilizing fields and clearing them of unwanted plants, pruning forests, combating human and ani-mal enemies, and eliminating dead, dry materials be-fore they can support a destructive major fire

Types of Fire Not all fires are equal Scientists distinguish five basic types in increasing order of intensity and destructive potential: those that smolder in deep layers of organic material; surface backfires, which burn against the wind; surface headfires, which burn with the wind; crown fires, which advance as a single front; and high-intensity spotting fires, during which winds loft burn-ing fragments that ignite separate fires Moreover, the intensity, likelihood, and range of fires for any locale depend upon the climate, season, terrain, weather

pecially the wind), relative moisture, and time since a

previous burn The dominant species of plant also

af-fects which type of fire an ecosystem can support

Tundra and Far-Northern Forests

Fires visit northern ecosystems infrequently because

they retain a great deal of moisture even during the

summer: There are intervals of sixty to more than one

hundred years between fires for forests and several

centuries for tundra Caused primarily by lightning,

light surface fires are most common Crown fires are

rare The seeds of many northern tree species, such as

pine and spruce, germinate well only on soil that a fire

has bared Fire does not occur in high Arctic tundra

and plays only a minor role in the development of low

Arctic tundra

Grasslands

Grasslands of all kinds rebound from surface fires

in about three years In shortgrass and mixed-grass

prairies, grass species, especially buffalo grass and blue grama, survive fires well, while small cacti and broadleaf plants succumb easily, assuring dominance

of the grasses For this reason, cattle ranchers fre-quently burn the prairies to remove litter and inedi-ble species, thus improving the distribution of grazing fodder In tallgrass prairies, big bluestem, Indian grass, and switchgrass increase after a fire, whereas cold-season grasses, such as Kentucky bluegrass, are devas-tated, and fires prevent invasions of trees and woody shrubs

Semidesert and Desert Regions Similarly, surface fires control shrubs in semidesert grass-shrub lands on mesas and foothills, while allow-ing the fire-resistant mesquite to flourish Desert sage-brush areas in the intermountain West have a surface fire about every thirty-two to seventy years A burned area takes about thirty years to recover fully, although horsebrush and rabbitbrush come back quickly

Wildfires, like this one in 1996 in Calabasas, California, are integral aspects of the natural cycles of life, but too often and increasingly they encroach on places in which humans dwell (AP/Wide World Photos)