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rimary Metals IndustryDavid Forrest and JulianSzekely

Reprinted from JOM, ol. 43, No. 12, December, 1991, p. 23-30.


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Warming and thePrimary Metals IndustryDavid Forrest and Julian Szekely

e: Global wa n i ng is the subject of a positiondeveloved bva nad hoccommitteeof the Ameri-a ~nsti tutef irk^, ~e t a l l u r ~ i c a l ,nd Petroleum Engi-will attempt touation of the issues surroundingclimate change. For more information, see thee 1991 edit ion of TMS News, page 42.This article is expanded from a unpublished presentationiven at thc ~ ~ ~ i p o n s o r e decond 1nternah;nal Sympo-'Materials,held

l%0, in ~ i l l i a m s b & ~ ,i r g n i aofs Note: It is inevitable that, as interest in the globalem increases, he specific role of the primary

article provides some helpful perspectives.The case for xlobal warm inx due to an-thropogenicsources of greenhouse gases isompelling, but i ts quantitative effects aretill scientifically unproven. Today, he U.S.rimary metals industry's carbon emissionsccount for slightly less than one percent ofthe global total. Further reductions are pos-ible through the implementation of existingenergy conservationmeasures, hrough moreextensive recycling, and by the developmentnd implem entation of al ternative process-ing technologies.

INTRODUCTIONThe phenomenon of global warmingand its consequences received wide-spread public attention and concernduring the 1980s.The scientific commu-nity has made a considerable effort tostudy the situation,'-" but there is stillwidedebate over how quickly theEarth'saverage atmospheric temperature ischanging and what the consequences ofthat change will be. Nevertheless, thegrowing body of evidence indicates thathuman activities are causing some de--gree of global warming.This article reviews the currentknowledge of global warming, quanti-fies the relative contribution of the U.S.metals processing industry to this prob-lem, and shows that recycling and alter-native processing technologies can helpto reduce carbon dioxide emissions.

A GLOBAL WARMING PRIMERThe Greenhouse Effect

The Earth's surface and lower at-mosphere are kept warm by what ispopularly known as the "greenhouseeffect." Like the glass of a greenhouse,gases in the atmosphere raise the tem-perature by absorbing and re-radiatingenergy back toward the Earth's surface.The net energy balance of this process iszero: the amount of energy received fromthe sun (340 W/m2 averaged over the

Earth's surface) s the sameas theamountradiated and reflected back to space (seeFigure 1). The greenhouse effect makesthe Earth's surface 33C warmer than itwould be o th er ~ i se .~ J ~rom space, theEarth would appear to be at an averagetemperature of -18C. This is becauselong-wavelength radiation from theEarth's surface is absorbed by cloudsand greenhouse gases, and much of thatis re-radiated back toward the Earth,making the true surface temperature(obscured from svace bv the clouds and

the height of the last glaciation, 20,000-40,000 years ago.I5(The drop in CO, wasmore likely a consequence of the ice agerather than a cause of it. Although thecauses of ice ages are not fully resolved,one explanation is periodic variations inthe Earth's tilt and orbit. As the Earthcooled, ice sheets grew and sea levelswent down; nutrient runoff from newlyexposed coasts increased phytoplank-ton productivity and trapped more CO,in the ocean; carbon was also trappedunder the advancing glaciers, in frozengases) a comfortible 1 5 k on average. ground, and in bog; ~ h i l eot the pri-Global Sources and Sinks of mary cause, reductions in CO, probablyGreenhouse Gases enhanced the cooling effects.)From about 1,000 years agountilaboutThe two largest contributors to thegreenhouse effect are water vapor andcarbon dioxide. Other gases, which con-tribute an additional 50% of the warm-ing effect of carbon dioxide by itself,include methane, nitrous oxide, ozone,and the chlorofluorocarbons (CFCs).14Trapped bubbles of air in Antarctic cecore samples provide records of atmo-spheric CO, levels over long periods,and measurements at Mauna Loa, Ha-waii, provide accurate data from 1958 odate. The carbon dioxide concentrationreached a maximum of 300 pl/l about130,000 years ago and fell to 200 pl/ l at

150 years ago, CO; concentration wasfairly constant at 280 pl/l. Since then,CO, levels have increased 25% (to over350 p1/1) due to human-related activitiessuch as fossil fuel burning, natural gasflaring,cement production, cattle ranch-ing, rice paddy agriculture, defores-tation, mining, and organic matterchanges in the ~ o i l s . ~ ~ J ~imilarly, meth-ane concentrations have doubled in thelast 200 years largely due to cattle andsheep ranching (43% of that increase)and rice paddies (34%of that increase).18The burning of fossil fuel is the domi-nant source of carbon emissions result-Reflected dlrectlyback Into spacefrom atmosphere

I I -fr 7036 infrared

Figure 1. The solar radiation budget and the greenhouse effect.12

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1850 1875 1900 1925 1950 1975 2000Year

2. Global and U.S. carbon dioxidection from fossil fuels, cement manu-ing, and natural gas flaring.19,20

ws the historical emissions of CO,to fossil fuel burning, cement pro-gas flaring. In 1984,Gt (billion metric tons) of carboncture and 0.4-0.8 Gt of car-

tropic^.^' Of the fossil fuel carbonwas assimilated by the oceans,and plant matter. It is importantfossil fuel carbon con-ution is just a small fraction of the

the atmosphere, and theve contribution has the ca-

f CO, and the climate as well.

Evidence of Global WarmingThere is wide agreement among sci-entists that greenhouse warming keepsthe Earth's surface at its current tem-perature. There is some debate over thepredicted increases in CO,, and there isconsiderable debate over the projectedclimatic changes resulting from thoseincreases. Arrhenius seems to have been

the first to calculate he temperature risedue to a doubling of CO,; he estimated a4-6C increase n average t em per a t~ re .~~Modern climate models predict an in-crease in average surface temperature of1.5-4.5C.24,25 hey also predict that,based onknownCO,emissions, he Earthshould be about 1"C warmer than it was100 years ago.26 n fact i t is about 0.5"Cwarmer, when surface emperature dataare corrected for the "urban heat isl andeffect,I2so the models seem accurate towithin about a factor of two.There are many difficulties in de-veloping good mathematical climatemodels, known as general-circulationmodels (GCMs), due in part to an in-complete understanding of the physicalprocesses i n v o l ~ e d . ~ ~ ~ ~ ~ ~ ~ ~o wit:We are currently unable to balanceall the fluxes of the global carboncycle over the past 200 years.We do not have a good under-standing of ocean uptake and circu-lation of CO,.We do not have good estimates ofthe "biological pumping" con-

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Figure 4. The variation of the Earth's surfacetemperature with tirne.13the observed warming is statistically in-separable from natural fluctuation^.^^,^^In summary, many (but not a1131,s35)researchers feel that increased CO, willsignificantly increase the Earth's surfacetemperature.The principal debates seemto be over these issues: How much willthe temperature rise for a given increasein CO,? How quickly will that occur?How will a given temperature increaseaffect weather patterns? What actionsshould be taken given the present un-certainty in projections?Consequences of Global Warmingand Policy Considerations

The effects of global warming on cli-mate patterns have been projected byseveral numerical models over the past15 years. Most of the models do notsimulate the transient effects of globalwarming; hey increase the CO, (usuallyby a factor of two) and let the model runto eq~ilibrium.~~aken together, themodels show that global temperatureswill rise 1.54.5"C over the next 50 years,which means that the planet will bewarmer than at any time during thehistory of our species.24While a few de-grees may not seem like much, given thetypical daily and seasonal variations, onaverage the Earth's temperature is ex-traordinarily constant. Several degreeschange in the average constitutes a ma-jor change in climate; cool the Earth'saverage temperature by 9C and youhave a full-blown ice age.

The model of Manabe et al. predictedthat bothdoubling and quadrupling CO,levels would produce a summer dry zonein the North American grain belt and amoisture ncrease in the monsoon belts.36(Because they omitted some ocean heattransport factors, the time scale for thesechanges s probably 100years rather thanthe projected several decades.) The re-duced precipitation and higher tem-perature they predicted would severelystrain water resources in the westernUnited States; crop irrigation would bereduced, resulting in lower yields.37Other models showed that, for CO,doubling, European emperatures couldincrease by 24 C in the summer and by

4-16C in the winter.24One study byManabe and Wetherald showed sum-mer temperatures in the United Statesup to 8OC warmer.38Oceans are pro-jected to rise 0.3 m +0.4 m by year 2100due to global warming (note the wideerror range in the proje~tion),3~ithpossibly significant consequences forcoastal regions.40Higher growth rates ofplants under increased CO, may help, asthe plants will incorporate more carbon,but increased radiation due to ozonethinning (because of CFCs) may sub-stantially reduce that benefitjlBecause of the uncertainties in themodels and the lack of a statisticallysignificant link between greenhouse gasemissions and global warming, somepolitical leaders are hesitant to take stepsthat may prove ~ o s t l y . ~ ~ ~ O t h e readers,particularly in Germany, Sweden, andthe Netherlands, are taking more activesteps to reduce greenhouse gas emis-s i o n ~ . ~ ~ , ~ ~ames Burke, a historian andauthor who has been active in the debateon global warming, says it does notmatter whether the greenhouse effect isactually occurring-as long as the con-sensus of scientific opinion says it willeventually occur, something should bedone now to forestall it.46

SOLUTIONSThe cost of controlling carbon dioxideemissions using existing technologiescould be hundreds of billions of dol-lar~:,~~ut reducing CO, emissions bystepping up energy conservation mea-sures could provide a cost savings. En-ergy conservation does not necessarily

lead to lower product costs, so indus-tries worldwide may not always takethis path on their own accord. Economicsolutionshave thereforebeen proposed:financial incentives and disincentives,steep taxes on energy, modest taxes onenergy, and an international market inemission permitsjRTechnological Solutions

Systems able to remove CO, from theatmosphere have been studied to vary-ing degrees, and Edmonds et a1.49providean excellent summary. Examples areabsorption and stripping of CO, usingliquid solvents, burning fuel to CO thencombining with a non-fossil hydrogensource to form liquid and gaseous fuels,burning oxygen and carbon diluted withrecycled CO, (resulting in concentratedCO, that can be recovered or disposedof), electrochemical decomposition ofCO,, and photosynthetic fixation of CO,in plants and trees. Disposal methodsinclude deep ocean dumping (environ-mental impact unknown), burying inthe Earth as solids or in spent wells as agas? and trapping carbon in seaweed orsalt desert plantation^.^^Long-term climate scenarios (e.g., 50to 100 years) are based on best estimates

of population growth, the resulting en-ergy requirements for that population,and the anticipated mix of energysources. These projections are primarilybased on current trends and do not ac-count for radical technologicaladvancessuch as the self-replicating molecularmachines (often referred to as nano-technology) described by Dre~ler.~I-~Like biological systems, nanomachinescould remove CO, directly from theatmosphere in a massively parallel dis-tributed manner, but with much greaterflexibility as to how the atoms are rear-ranged (carbides and diamond). Beforecommitting hundreds of billions of dol-lars toward mitigation technologies-inorder to avert or delay a climate disaster50 years in the f u t u r e w e should assesswhether such a technology could ma-ture in 20-30 years and solve the prob-lem more cheaply, cleanly, and effec-tively. Although one should never as-sume that future technologies can solvetoday's problems, it is possible to makeengineering projections from knownphysical laws and estimate bounds onsystem~apabilities.~~hile some of theseengineering calculations have alreadybeen made for nanotechnology, an au-thoritative time frame assessment is stilllacking.Financial Incentives andDisincentives

Financial incentives for energy con-servationhave beenwidely implementedat both the state and federal levels forsome time. On the whole, they have notbeen effective for a variety of reasons. AsHu points the effects of the federallegislative programs (e.g., the NationalEnergy Act of 1978 and the Crude OilWindfall ProfitsTax Act) have conflictedwith eachother, generally canceling out.Norman Dean has analyzed the ef-fectiveness of various state financial in-centive programs for increasing in-dustrial energy efficiency.'jO Raising en-ergy prices appears to be the bestincentive, since this leaves all the in-vestment decisions up to the business,but large price increases would be metwith heavy political opposition; also,states must account for the resultinghardships placed on citizens as well asmarginal businesses. State financial in-centives, although politically more pal-atable, again did not seem to be effectivein practice. These included tax subsi-dies, direct subsidies, loans, bond fi-nancing programs, and state credit cor-porations. One study of various eco-nomic incentives and financing optionsto stimulateenergyc~nservation~~oundthat investment tax credits and costsharing were the most helpful tactics formetal producers.A final point on incentives is that dif-ferent tactics may be needed for differ-ent kinds of metal producers. The alumi-

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num companies already devote a largefraction of their R&D efforts toward en-ergy conservation, while the steel com-panies have historically focused moreon quality control and new products.62The latter should therefore benefit morefrom increased support for energyR&D.Taxes on Energy

The underlying philosophy behindcarbon emission or energy taxes is thatcurrent energy prices do not reflect thehidden costs to the environment, so aneffective solution must somehow im-pose those hidden costs (see, for example,Reference 63). Steep taxes on energyconsumption may be effective but couldcause economic hardships and maytherefore be rejected by many nations. Aodest tax-with the revenues directedoward energy conservation measures,inding replacements for CFCs, and re-orestation-may be more practical.Some of those who have studied glo-rove energy efficiency as one methodoreduce carbon dioxideemissions, sincet "usually makes economic sense"" tomplement those measures anyway.

Unfortunately, if energy prices are artifi-cially low (i.e., if prices do not reflectcosts to the environment), economicanalysis may show that it does not pay toimplementsomeconservationmeasures.H u ~ ~tudied the economics of threedifferent energy conservation measuresin the copper industry: using recycledscrap, flash smelting, and retrofittingreverberatory smelters with oxygenlances. His analysis showed that theproduct cost would increase in all threecases. Under 1974 price structures, theenergy prices would have had to doubleto achieve economic breakeven. Such amarked increase due to increased taxeswould severely disrupt the world econ-omy, and efforts to enforce this interna-tionally would therefore probably fail.A less radical energy tax has beenproposed by physicist JoseGoldemberg,Brazil's secretary of state for science andte~hnology .~~e believes that a world-wide levy of $1 per barrel of oil equiva-lent or $6 per tonne of coal equivalent,which would generate about $50 billionper year, couid be used to finance thefollowing measures to reduce green-house gas emissions: the phase-out ofTable 1.1968 and 1985 Energy Consumption and Carbon Emissions of U.S. PrimaryMetals Manufacturing Sector

Quantity Electricity Coal Natural Gas Oi l- -968 Energy Consumed (PJ)* 454 2,992 910 3221985 Energy Consumed (PJ)t 506 1,191 727 531968 Carbon Released (M t) * 25.9 71.2 12.5 6.21985 Carbon Released (M tY 26.2 28.4 10.0 1OData taken from Reference67.Data taken from Reference 68.Based on conversions in Reference69, and relative contributions of coal, oil, and gas to electricity generated in Reference70.

6.9% 9.7% 2.1%

ElectricityaCoalNatural Gasoil 1.5%

b dFigure 5. Graphs showing the change in the U.S. primary metals industry's energy consumptionand carbon emissions from 1968 to 1985. (a)Energy consumption in 1968,4.678exajoules (EJ).(b ) Energy consumption in 1985, 2.477 EJ. (c)Carbon emissions in 1968,115.8Mt. (d) Carbonemissions in 1985, 65.6 Mt.

chlorofluorocarbons ($700 million peryear), reforestation $15 billion per year),and energy conservation ($30 billion peryear). Roughly half of the energyconser-vation funds would be directed to less-developed countries. The tax is not pri-marily meant to discourage energy con-sumption; it is meant to "be a fair andeffectiveway to raise the money neededto fund a transition into an ecologicallymore benign economy." Based on thesenumbers, we estimate that the cost to theU.S. primary metals industry would beroughly $300 million per year. This turnsout to be about 1% of the $30 billionwhich would be available for energyconservation, oughly the same percent-age as the global carbon emissions by theindustry. (We are not sure how much ofthat amount would be made available tothe industry under Goldemberg's plan.)Trading Carbon Equ ity UnitsA somewhat different approach hasbeen endorsed by the Brookings Institu-t i ~ n ~ ~nd Burke.46The Brookings Insti-tutionrecommendation would giveeachnation a certain number of carbon equityunits, based on projections of populationand future economic activity. As nationsburn carbon, they use up their units.When they run out, they must purchaseadditional units from other nations(Third World nations will have an ex-cess).Burke's preference, based ona 1989Dutch government report, is similar,except that instead of cash the carbonunits buyers must trade technology. Thiswill allow the less-developed nations toleapfrog inefficient technology,purchasehighly efficient systems, and power themwith renewable energy sources.GLOBAL WARMING AND THEMETALS INDUSTRY

The Metals Industry's Contributionto the Greenhouse EffectIt is convenient to lump fossil fuelburning into one combined category, sothe data on human contributions to at-mospheric carbon are usually presentedin this manner.15J9,22or this study, wesought to quantify the relative contribu-

tion of the U.S. metals processing indus-try to carbon emissions, so we devel-oped the data in a different manner us-ing some of the same sources.Figure 5 shows the contribution for1968 and 1985, broken out by energysource. (Industry-wide data, shown inTable I, were readily available for theseparticular years and were used to de-velop the graphs in Figure 5.) Overall,the gross energy consumption of theprimary metals industry was reduced53% between 1968 and 1985. An evengreater reduction (57%) n carbon emis-sions was realized, aided by an 11%decrease in the amount of carbon re-leased per unit of electricity consumed.In 1968 the U.S. primary metals sector

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ed 115.8 Mt of carbon to the atmo-re, 2.7% of the global total; in 1985ped to 65.6 Mt-about 0.8% toof the global total.Table I1 provides a more detailed ac-f carbon sources. Carbondue to three major factors:A 32% reduction in total steel out-put (22 Mt carbon).A doubling in electric arc furnace(EAF) steel production from 15.4Mt to 30.2 Mt steel (4 Mt carbon);this displaced some basic-oxygenfurnace (BOF)and open-hearth steelproduction.The balance (7.7 Mt carbon) is pre-sumed to be due to energy conser-vation measures and improvementsin operating efficiency, principallyblast furnace operations, continu-ous casting, direct charging androlling of ingots without cooling,and waste heat recovery.7nCarbon emissionsfrom aluniinum andby 36%Mt) from 1968 to 1987 despite pro-ion increases of 44% for aluminumfor copper, due to:Reduced use of coal (11 Mt carbon).Greater use of recycled aluminumscrap, from 20% o 30%of total ship-m e n t ~ ~ ~1.5 Mt carbon).An 11% reduction in the amount ofcarbon emitted per unit of electric-ity generated from fossil fuels (1.2Mt carbon).Other efficiency improvements (-7Mt carbon, although this is difficultto evaluate because of uncertaintiesin the mix of hydropower and fos-sil-fuel electricity consumed foraluminum processing).These numbers reflect the metalss successful continuing efforts

fforts are wel l-d ~c ur nen ted ~~ ~~ ~nd in-e the development of the Alcoaf forced convection inverberatory furnaces (25%

en erg^),^^,^^ the use of prebakedof the Asarco shaft furnace for

the development of the flash% ess energy thaneverbatory furnace)F8 continuousting of steel (5.5% less energy),s6 m-

oxygen lancing, foam-practices, and high-power, ong-0peration) ,8~,~~ncreased efficiency of

d dry quenching of coke.91Further energy savings are possiblerocesses use much more

energy than dictated by their thermody-namic minimum values (by a factor ofabout two for steel and about three foraluminum).92We should remark herethat the energy consumption involvedin metals production may vary quitewidely from country to country, evenwhen seemingly similar technologies areinvolved. Table 111 shows that the en-ergy consumed per tonne produced var-ies by nearly a factor of two amongWestern nations. Here is an importantcaveat to this data from its source:93This industry's structure in any particularcountry is determined not solely by the numberof joules required to produce a ton of steel but isrelated to local conditions,and specifically to theavailability and cost of various types of energy.

The different productionroutes require differentforms of energy, and it is the relative deliveredcosts of the varioustypesof energy which deter-mine the most economical process in a particularlocation. Hence a higher energy consumptiondoes not automatically imply that a particularcountry's industry is inefficient or uneconomic.The latter observation points toward asolution for global warming which in-volves economic pressures favoring amore thermodynamically efficient in-dustry. This would be most effective inthe least "efficient" countries toward thebottom of the list in Table111, and possi-bly also in the Soviet Union as it convertsto a. market-based economy. Efficiencyimprovements in the People's Republicof China, however, would probably re-quire a political mandate.

Table II. Carbon Released by Sectors of the U.S. Primary Metals Processing IndustryWei ~ht f Carbon Released (Mt)

Factors Causing Carbon Release Ref.GlobalFossil Fuel Burning and Cement

ManufactureDeforestation and Other Land UseUnited StatesFossil Fuel BurningSteel ProductionCrude Steel ProductionCoal ConsumptionBlast Furnace LimestoneNatural Gas ConsumptionFuel Oil ConsumptionPurchased Electricity*Subtotal

Ref.-

Aluminum and Copper ProductionPrimary and Secondary A1 5.33 76 3.69 73Primary and Secondary Cu 2.04 76 1.78 73Coal Consumption 2.5-3.0 74,75 13.9 73Natural Gas Consumption 6.3 75 4.0 73Fuel Oil Consumption 0.57 75 2.3 73Purchased Electricity* -9.5 9.6Subtotal 18.9-19.4 29.8* Using factors of 5.082 x 1CFkg carbon per joule electricity (1987) and5.702 x 1lFkg carbon per joule electricity 1968).The1987

number is from References 70 and 77, and the 1968 number is from References 70 and 73. Self-generated electricity is notcounted, since purchased oil, coal, and gas is already counted, and self-generated hydropower would not emit carbon.

Table Ill. Net Energy Requirements of the Steel Industryg3- .1 9 8 5 1 9 8 M 9 8 5 Processes Used in 1985 (% )Nation (GT/tcs)* Change (% ) BFlBOF EAF Other- - -pain 15.5 -17.8 39 61 0

Netherlands 17.6 -9.6 100 0 0Japan 17.7 -9.3 71 29 0Italy 18.2 -3.9 48 52 0Sweden (1984) 18.9 -25.6 48 52 0Luxembourg 19.2 -1 1.7 100 0 0Brazil 20.6 Not Avail. 72 25 3Finland 20.7 +0.7 83 10 7Austria 20.8 -8.5 99 1 0United Kingdom 21.2 -9.4 72 28 0Canada 21.3 -7.0 86 14 0Belgium 21.4 -3.4 93 7 0West Germany 21.6 -3.6 82 18 0United States 22.3 -13.6 59 33 8Australia 22.4 -10.6 99 1 0France 22.4 -7.8 82 18 0South Africa 29.0 -7.7 69 26 5Soviet Uniont -30 - - - 52Chinat 52.5 - - -

tcctonnes of crude steel.t The statistics for the Soviet Union and China are from Reference 94.

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Scrap and Energy (also called "obsolete" scrap) is gener-ated from uroducts that have comuletedIf one looks at the published numbersor energy consumption in materialsrocessing operations, there is littledoubt that there are dramatic benefits torecycling (secondary production) ver-sus producing metal from ore (primaryproduction). The data in Table IV showenergy reductions of 61% to 94% whenprocessing scrap instead of ore. This cor-responds directly to reductions in car-bon dioxide emissions.When analyzing recycling benefits, itis important to make some distinctionsregarding the type of scrap. Home scrapis the waste produced within a fabrica-tion plant: ingot discard,risers, shearingsand trimmings, rejected material, and soon. It is recirculated within the plant andrarely shows up in published statistics.New scrap (also called "prompt" scrap)is generated by the users of semifinishedsteel; it includes turnings, borings, trim-mings, and rejected material. Old scrap

Itheir useful life cycle: aluminum cans,steel rails, automobiles and farm equip-ment, dead batteries, structural mem-bers, etc. The data in Table IV are pertonne of output, so it includes the fuelused to recirculate he home scrap (up o50% of total th r o ~ g h p u t) . ~ ~usik andKenahany7 stimated that one-third ofthe raw steel produced was recycled ashome scrap in 1978. Current numbersare probably much lower due to theincreased use of continuous casters.Chapman and Roberts98have ana-lyzed the interplay between resourcesand fuel consumption. Figure 6 is asimple material flowsheet which sum-marizes an important point-generat-ing and recycling home scrap and newscrap does not decrease the amount ofraw ore required to satisfy the demandfor a product. Only the generation of oldscrap can reduce that amount. Further-more, recirculatingnew and home scrapTable IV. Enerav ln ~u tor Various Metals: Primarv vs. Secondarv Productiong5

Metal-teelCopperAluminumZincLeadTitanium

Primary ProductionAssumptionsAverage production inbasic oxygen furnace1% ore (best)0.3%ore (worst)From bauxite5% ore2% oreFrom beach sands

Secondary Production(GJA) Assumptions-.7 100%scrap in electricarc furnace

13.0 High-grade scrap37.0 Low-grade scrap16.5 Average scrap24.0 Average scrap9.0 Average scrap140 Includes refining alloys

Fabrication Product ConsumerproductsOres !

/ --.

\ 1 Horn9'. scrap

4 New Scrap/ I 1

..-.---------------------------'Figure 6. A diagram showing that the generation o new scrap does not reduce the demand forraw materials.98

t

Direct fuel use Direct fuel useE, Iton through Em ton through

---------------------------------------//Figure 7. A hypothetical system with steel producer and auto manufacturer. The recirculatingscrap increases fuel use bu t does not affect the amount of pig iron per ~ a r . 9 ~

increases the energy consumed per unitproduct. In Figure 7, this concept is ap-plied to the GER (gross energy require-ment) to produce a car:

-- ---.- .,"/

GER = Ec= Ep+ (1 + a)(E,+ Em) (1)

- -- --- - --- - - -- --- -

where Ec is the energy required to pro-duce the car, Ep s the energy required toproduce the pig iron input into the steel-making furnace, E, is the energy con-sumed in the steelmaking furnace, Em sthe energy required to manufacture thecar, and a is the tonnage of recirculatedscrap per unit output. Chapman andRoberts point out that it is possible thatboth the steel producer and the carmanufacturer could conclude that itwould be cheaper to invest in equipment

I v v 8

which uses or produces more scrap, butthat these decisionswould actually resultin a higher GER per car.yyThe analysis of mixed primary andsecondary production is only slightlymore complex. Figure 8 illustrates thiscase. The GER is given by

IIton pig iron jger j *II

GER = f ( l + a)(l+ P)(F,, + F,) +(1- f ) ( l a)(l+ P)FSs+(1+ P)F,+ Fp (2)

where f is the fraction of product fromprimary production, (1- ) is the fractionof product from secondary production,a is the tonnes of home scrap per tonneof output, p is the tonnes of new scrapper tonne of output, and Fx is the fuelrequirement for process x (the processesare defined in Figure 8).Equation 2 also shows that the morehome and new scrap, the higher theGER. Since the fuel requirement for pri-mary production (F,,,,,,+ F,) is muchgreater than that for secondary produc-tion (FJ, the GER is very sensitive to themix of primary and secondary produc-tion. This is not to say that recyclinghome and new scrap is useless-throw-ing it away would only increase the frac-tion of product made from ore (f), in-creasing the GER even more.Thus, if all stages of the process aredesigned to generate less home and newscrap, then the total amount of energyper unit product goes down, and so doesthe cost, and so do the carbon dioxideemissions. Likewise, increasing theavailability of old scrap can reduce de-pendence on high-GER primary pro-duction. Old scrap availability is limitedby the efficiency of scrap recovery(sometimes as low as35%) nd dependson consumption growth versus productlifetime (slower growth and shorterlifetimes increase availability).Anotherpoint is that product design changes canimprove recovery efficiency, but thechanges may increase the productmanufacturing cost while the scrap re-coverer and the metals producer reapthe benefits of the increased efficiency.While these resource and energy issuesmay seem basic to those in the recycling

I IIt a tons scrap /'Sfee lfurnace

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1 + a' tons*

C arpressIIIII Car outputi - (1 ton steel)I ger EcI


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Secondaryscrap productlon

4 I I > IOres Primary Fabrication +* production manufacture--, ton

Figure 8. Fuel and metal flows for mixed primary and secondary prod~ction .~~community, it is important to reiterate sufficient markets for old scrap productsthem here since they are rarely men- which have limited applications becausetioned in the global warming literature. of higher contaminant levels.The Estimated Benefits of Recyclingto Carbon Emissions

Given a known amount of unrecov-ered old scrap, it is possible to estimatehow much carbon emissions would bereduced if this old scrap were recoveredand processed (thereby reducing thedemand for ore). These estimates ignorethe practical problems like sufficient ca-pacity to process all the old scrap andTable V. Technological Alternatives toIron Makina

Carbon EmissionMethod (kglt Iron)Blast Furnacelo3,107 500K-R Processlo4


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43. Janet Raloff, 'Why the White House Prefers to Wait,"Science News, 136 (16 December 1989),p. 395.44. R. Monastersky, "Buying Time in the War on GlobalWarming," Science Nm s, 139 (23 March 1991), p. 183.45. Janet Raloff, "Governments Warm to Greenhouse Ac-tion," Science News, 136 (16 December 1989),pp. 394ff.46. James Burke, "After the Warming," television program,Maryland Public Television and Film Australia (1990).47. Ref. 23, p. 42.48. Joshua M. Epstein and Raj Gupta, "Controlling theGreenhouse Effect,"Brookings Occasional Papers (Washing-ton, D.C.: Brwkings Institution, 1990).49. Ref. 9, p. 572.50. "Saltv Farms for Stor ine Global Carbon." Science News.

85. V. Subramanian, "Efficiency of ReverberatoryFurnaces,"Energy Consmation in Industry-Combustion, Heat Recov~ryand Rnnkine CycleMachines,ed.H. Ehringer, G. Hoyaux, andP.A. Pilavachi (Boston, MA. D. Reidel Publishing Company,1983),pp. 6-20.86. Ref. 61. o. 224.

so tha t ho m e sc rap p rodu c t i ons m i n i m i zed ) will a ls o h e l p o m i n i m i z emiss ion o f greenhouse gases .ACKNOWLEDGEMENTS H7.11.~I.~eilog,"UeltrngCath0deCopper-ACaseS~dynI'roms Fnerav Efficiencv," in Kef. 81, DD. 87-99.Thanks to Dr. Gregg Marland (Oak RidgeLaboratoy Carbon Dioxide Infor-Ce nter ) for providingents on the manuscript and for recent

Iron and Steel Institu te) forL. Cather for comm enting on the

.88. Ref. 59, pyi33.89. MarcH. Ross and Danielsteinmeyer, "Energy for Indus-try," Scientific American, 263 (3) (1990),pp. 88-98.90. R.J. Fruehan, "Scrap in Ironand Steelmaking," in Ref. 79,pp. 13-34.91. H.W. Lownie, Jr., "Potential for Energy Conservation inthe Steel Industry," Alternative Energy Sources for the SteelIndustrw, ed. Tulian Szekelv (New York: Marcel Dekker.139 (16 arch 1991), p. 175:51.K. Eric Drexler, "Molecular Engineering:AnApproach tothe Development of General Capabilities for Molecular Ma-nipulation," Proceedings of the National Academy of Sciences,vol. 78 (1981).DD.5.275-5.278. i 9 m , pp. 99-io5.92. Ref. 61, p. 9793. International Iron and Steel lnstitute Committee on Sta-52. K. Eric ~r & le r , when Molecules Will Do the Work,"Smithsoninn (November 1982), pp. 145-155 .53.K.EricDrexler,EnginesofCreation(NewYork:Doubleday,1986).54. K. Eric Drexler, "A Technology of Tiny Things:Nanotechnics and Civilization," Whole Earth Revim (Springl QR 7 )

tistics, Stattstics on Energy In the Steel Industry 1980-1985(Brussels, Belzium: IISI, 1987). D. 2.91. D.F. ~nd&son, nvatr commun~cat~on13 June 1991).Data lncludcd trom Thr Yrnrbook of Inm and Steel Indu~tyfClrina (Reillnz.China: Metnlluraical Industrv Press. 1YRY).otes and Referencesnal Research Council, Carbon Dioxide and Climate: Aic Assessment (Was tinaton, D.C.: National Academv 95. P.F. ~6 a f i a n nd F. ~obe rg, e t n lesoircesnd Energy(Boston, MA: Butterworths, 1983),p. 138.96. Ref. 95, pp. 138-139.97. Charles L. Kusik and Charles B. Kenahan, Energy UsePatterns for Metal Recycling, U.S. Bureau of Mines informa-tion circular 8781 (1978).98. Ref. 95, especially chapters 8 and 11.99. Ref. 95. DD.18M81.

A ,.55. K. Eric Drexler. "Nanomachinerv: Atomicallv Prease.1: Pearman, ed., Carbon Drox~du nd Climate: Australianesearch, ed. G.I. Pearman (Netley, South Australia. Austra-Gnffrn Press Ltd., IYXOJ.. Kellogg and Kobert Schware, Cltmate ChangeCO Westview Press. 1961).

Gearsand Bearings,'" Proceedtngs of ~ I I ~ ' I C E EMicro dobatsandTeleoacratorc Work~hovNew York: Institute of Electrical and~le ctk nic s ngineers, 987).56.A. K. Dewdney, "Nanotechnology: Wherein MolecularCo m~ ut er s ontrol Tinv Circulatorv Submarines." Scientificarbon ~ioxide~evid,1982NewYork:ChangingClimate(Washington,National Academy Press, 1983).A.J. Crane, Man-Made Carbon Dioxideand Cli-

ds. , Carbon Dioxide: Current Views and De-in Energy/ClimafeResearch (Boston, MA: D. Reidelbalka, ed., Atmospheric Carbon Dioxide and thebal Carbon Cycle, U.S. Dept . of Energy report DOE/ER-9 (December 1985).A. Edmonds et al.. Future Atmosvheric Carbon Dioxide

~m ehcan, 58 (1) (19886 pp. 100-163.57. K. Eric Drexler, "Rod Logic and Thermal Noise in theMechanicalNanocomputer,"MolecularElectronicDevices,ed.Forrest L. Carter, Ronald Siatkowski, and Hank Wohltjen(New York: Elsevier Science Publishers. 1988).DD. 39-56.

100. Ref. 9'5:pp. 131.101. Ref. 76, p. 112.102. Robert A. Frank, Charles W. Finn, and John F. Elliott,"Physical Chemistry of the Carbothermic Reduction of Alu-mina in the Presence of a Metallic Solvent: Part 11. Measure-58. K. Eric Drexler, "Exploring Future ~echnoldg'ies,"DoingScience, ed. Iohn Brockman (Enalewood Cliffs, NT: Prentice

ments of Kinetics of Reaction," Met. Trans. B, 208 (19891, p.1c.1."..103. Michiharu Hatano et al., "New Ironmaking Process byUse of Pulverized Coal and Oxygen," Novel Iron and Steel-Hall Press, i991), pp . 73-92. -59. S. David Hu, Handbook of industrial Energy Conservation(New York: VanNostrand Reinhold Co., 19831, pp. 227-231.60. Norman L. Dean, Jr., Energy Efficiencyn Industy (Cam-bridge, MA: Ballinger Publishing Co., 1980). pp. 73-107.61. Melvin H. Chioeioii. ndustnal Enerm Conservation (New 10-1. R: ~ & knd J. Fl~ckenschild, KR-Process Hot MetalProduction on the Has~sof oals," In Ref. 103. pp. 1031-1039105. W-K. 1.u. ('. Rrvk. and I1.Y. C;ou. 'TheLH Furnace forStrategies ( ~ & k idge, NJ: Noyes

Anver Ghazi. eds.. Carbon DioxideYork: Marcel ~e&r,'l nc., 1979), p. 56 y62. Ref. 61, pp. 573-574.63. Harold M. Hubbard. "The Real Cost of Enerev." Scientific

Smeltlng ~ed;chon;f IronOrcs," in Ref. 103,pp. 1031-1039.Id6. 1:ranzOetersand Alpayd~ nSaa to,Some FundamentalAsocctr uf Iron Orc Reduction with Coal: in Rcf 103. on..reenltouse Cases Chmatrc and Assocrated Impactsic Publishers. 19R9)",American, 264 (4) (1991j, pp . 36-42.64. Ref. 13, D. 78.

...10i1-1039.107. United States Steel Corp., The Making, Shaping andTreating of Steel, 9th ed. (Pittsburgh, PA: Herbick & Held,19711, pp. 78-79. Assumes that all of the fixed carbon in thecoal is eventually converted to CO,; intermediates are CH,CO, and coke breeze, which are subsequently burned orsintered. Thevaluesvarywidely (61-84percent), dependingon the mix of low-, medium-, and high-volatile coals andtheir moisture contents.108. Sven Eketorp, "Energy Considerations in ReductionProcesses," TheFutureof the World's Steel lndustry, d. JulianSzekely (New York: Marcel Dekker, 1976), pp. 2 343.109. R. Kieger and B Schaffar, "C-FFOX: Steelmaking byPreheating and Oxidizing Melting of Scrap," in Ref. 103, pp.1079-1082.

StephenH. Schneider,Clobal Warming(SanFrancism,CA:H. Schneider. "Climate Modeline!' Scientific

65. Ref. 59, p.133.66. Jose Goldemberg, "How to Stop Global Warming,"Technolow Review. 93 (8) (1990).oo. 2431.".mer rich, 256 (5) (1987), 78.Stephen H. Schneider, "Thechanging Climate," Scientificpp. 7&79.J.A. Laurmann, "Future Energy Useand GreenhouseGasatic Warmine." in Ref. 10. DD.101-131.

67 Stanirrd Research lnstitute,bdttcrns of Energv Consumptron rtt tltr. United Stntes (Washinaton, D.C.: Office of Scienceand Technology, 1972),p. 83. -68. U.S. Dept. of Energy, Annual Energy Review 1989, EnergyInformation Administration report DOE/EIA-0384(89) (24May 1990), p. 37.69. Greaa Marland, "The Im~ actf Svnthetic Fuels onGlobalW.M. Post et al., "The Ydlobal ~a rb b; l' ~~ cl e, "mericantist, 78 (4) (19901, pp. 310-326.. 11, p. 28.

M.A.K. Khalil and R.A. Rasmussen, "Trends of Atmo-Future," in Ref. 10, p. 95.ataby Rotty as showninJulia A. Watts, "The: Data Sampler," in Ref. 4, p. 457-

Carbo"'bioxrde ~ mis sio ns? n Ref 4, pp. 40M10 .70. U.S. Dept . of Energy, Annlral t.nnqy Kn'rnc, 1989. Energylnfor mat~ on dministration reoort ME/EIA-03&1(89) 24.May 1990).71. Estimated from reconstruction figures in Ref. 1572. Iron b Steelmaker, 17 (13) (1990),p. 24.73. Ref. 67, pp. 83ff.74. Intemahonal Enerev Aeencv. Enerw Balances of OECD

110. L.V. Bogdandy et al., "Oxygen Converter Steelmakingwith High Scrap Rates," in Ref. 103, pp. 1083-1094.111. Gregg Marland, private communication (31 October1990).

. R.A. Houghton et al., "Carbon Dioxide Exchange Be-sphere and Terrestrial Ecosystems," in Ref.

il FuelCombustion: Trends, Resources, and Technologi-. White, "The Great Cl imate Debate," Scientifican, 263 (1) (19901, pp. 37.Session 111: Expected Climaticn Ref. 10, pp . 135-137.

e News, 136 (26 August 1989), p. 132."CO,: Where It Goes ,Nobody Knows," ScienceNms,139ch 1991), p. 191.12. D. 74.

Other Sourcesountries 1987-1988 (~ ri s: "o ~C 'b /1 ~ ~1 9 9 0 ).u k b e r snthis reference were divided by the approp riate factor in theappendix to convert from tonnes of oil equivalent and werethen multip lied by 0.70 to determine the mass of carbonreleased from that amount of coal. The 70 wrc ent value wasFrost, Paul D., Raymond W. Hale, and Thomas J. McLeer."Energy Consumption in the Primary Production of Met-als." Iron and Steel Engineer, 56 (4) (1979), pp. 50-56.Fenner, S.S., and L. Iceman, Dmands, Resources, Impact,Technology, and Policy. Vol. 1 of Energy. 2nd ed. Reading,MA: Addison-Wesley, 1981.Russell, Clifford S., and William J. Vaughan. SteelProduction:Processes, Products, and Residuals. Baltimore, MD: JohnsHopkins University Press, 1976.Szekely, Julian, ed.The Steel Industry and the Energy Crisis.New York: Marcel Dekker, 1975.U.S. Dept. of the Interior. Energy Perspectives2. June 1976.U.S. Dept. of theInterior. Energy Perspectives. February 1975.

used in Ref. 22 and is also consistent wit6 Ref. 107.75. Estimated from 1985 values in Ref. 68, assumina thatfrrrousand nunft.rrousmetalswereconsumed in proportionssim~laro the 1968 \falues.Thc 1985 values are closc to 1987values since production levels were also close for those twoyears.76. U.S. Dept. of the Inter ior, Minerals Yearbook 1988, vol. 1(Washington, D.C.: U.S. Government Printing Office, 1990).Al, p. 109; Cu, p. 310; Zn, p. 1019.77. U.S. Dent. of Commerce. 1987 Census of Manufacturers.lndustry sdnes, "Smeltlng and Rehnlng of q on fe kus Met-ahand Allovs"(industries3331.3334.3339.3341Jand BlastFurnaces. Steel Workr. and Kolline and Finrshine Mrlls" ABOUT THE AUTHORS-0. Ref. 5, pb.270-284on of COiInduced Climate Change," in Ref. 10, pp. (industries 3312,3313,3315,3316,3~17)1987).78. R.L. Whiteley and R.E. Storat, "Energy Savings in theSteel Industr)" (paper presented at the ASM Conference onMaterials for Future Energy Systems, Washington, D.C., 1-3 May 1984).79. Jan van Linden, "Aluminum Recycling, From Junkyardto Boardroom," Recycle and Secondary Recovery of Metals, ed.P.R. Taylor, H.Y. Sohn, and N. Jarrett (Warrendale,PA: TMS,1985). pp. 35-45.80.M.C. Flemings, K.B. Higbie , and D.J. McPherson, Reportof Conference on Energy Consnoation and Recycling in theAluminum Industry, conference held at Massachusetts Insti-tute of Technology, Cambridge, MA, 18-20 June 1974.81. Y Austin Chang, W.M. Danver, and J.M. Cigan, eds.,Energy UseandConseruation in theMetalsIndustry (NewYork:The Metallurgical Society of AIME, 1975), pp. 101-120.82. Allen C. Sheldon, "Energy Use and Conservation inAluminum Production," in Ref. 81, pp. 157-171.83. Mahesh C. Mangalick, "Improvement in Thermal Effi-ciency of Aluminum Reverbatory Furnaces," in Ref. 81, pp.101-120.84. Richard J. Reed and Robert W. Marshall, "UpgradingAluminum Scrap Melter Operation," in Ref. 79, pp. 397-406.

Dav id Forrest earned h is M.S. in ma terialsscience and engineering at Lehigh Universityin 1985. He is curren tly completing his doc-toral degree in materials engineering at theMassa chusetts nstitute of Technology and isa research specialist at Allegheny LudlumSteel in Brackenridge, Pennsylvania. Mr.Forrest is also a member of TMS.

od B Idso, Carbon Dioxide: Friend or Foe? (Tempe,: IBR Press, 1982). der, "A Sizzling Scientific Debate;Claim That the Evidence forGlobal Warming isNo tHot," Time. 135 (30 April 1990). D. 84." N ~ W ree nh bu se eport Puts DownScience, 249 (3 August 1990), p. 481.77. Ju lia n Szekely earned his Ph.D. in chemicalengineering at Imperial College, London, in1961. He is currently a professo r of m aterialsengineering at the M assachu setts nstitute ofTechno logy. Dr. Szekely is also a member ofTMS.

Ref. 5,;;. 46..F.B. Mitchell, "Simulation of Climate Change Due toases of CO," in Ref. 10, pp. 1 W151 .. Monastersky, "Predictions Drop for Future Sea-LevelNews, 136 (16 December 1989), p. 397.

se,'" Science Nm s, 136 (26 August 1989),p. 134.. R. Monastersky, "Bush Holds Cautious CourseonGlobalScience News, 137 (28 April 1990), p. 263.

forrest_primary_metals_global_warming_1991_ocr

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