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U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Measurement Laboratory

Fracture and Deformation Division

Washington, DC 20234

July 1982

issued September 1982

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U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU of standards

NBSIR 82-2571

RECYCLING MUNICIPAL FERROUS

SCRAP

J. G. Early

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Measurement Laboratory

Fracture and Deformation Division

Washington, DC 20234

July 1982

Issued September 1982

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Director

TABLE OF CONTENTS

Page

ABSTRACT ii

INTRODUCTION 1

FERROUS SCRAP HISTORY 1

SOURCES OF FERROUS SCRAP 5

ROLE OF FERROUS SCRAP IN MODERN STEELMAKING PROCESSES 7

RECYCLYING FERROUS SCRAP FROM MUNICIPAL SOLID WASTE 12

IMPEDIMENTS TO INCREASED USAGE OF MUNICIPAL FERROUS SCRAP 14

MARKETS FOR MUNICIPAL FERROUS SCRAP 16

Iron and Steel Production 17

Iron Foundries 18

Ferroalloy Production 19

Detinning and Copper Precipitation 19

ROLE OF STANDARDS 21

TRENDS 22

REFERENCES 24

TABLES

1. Total Ferrous Scrap Consumption by Industry 27

2. Modern Steelmaking Production 28

3. Typical Composition of Municipal Solid Waste 29

4. Steel Production and Scrap Consumption in the U.S 30

5. Tramp Element Levels in Municipal Ferrous Scrap 31

ABSTRACT

The secondary metals industry associated with the recycling of ferrous

scrap is tied to the development in the 1850's of the acid-Bessemer

furnace, the first large capacity steelmaking process. Within twenty-five

years of this development, the recycling of ferrous scrap became an

established industry. Changes in steelmaking technology since World War

II, especially since the 1960's, are impacting the traditional ferrous

scrap industry. The increased demand for old scrap is due to growth in

electric-arc furnace steelmaking capacity, reduced availability of home

scrap and prompt industrial scrap, and larger scrap exports. Ferrous scrap

recovered from municipal solid waste is one of the new sources of old scrap

that may satisfy these increased demands. Systems for the recovery of the

ferrous fraction from municipal solid waste have been developed, although

increased usage of municipal ferrous scrap has been very slow due to

institutional and technical barriers. The technical barriers posed by the

physical and chemical characteristics of municipal ferrous scrap strongly

inhibit the development of markets for this new material. The real and

potential markets for increased consumption of municipal ferrous scrap are

discussed in terms of these barriers together with the important role of

standards for municipal ferrous scrap in improving communications between

buyers and sellers.

ii

Introduction

In any analysis of recycling, it is necessary to place in perspective

the industries which consume or could consume the recycled material and the

existing relationship between the suppliers of the recycled material, the

secondary materials industry, and these consumers. This discussion,

limited to iron and steel scrap (that is, ferrous scrap), focuses on the

individual markets for scrap, their historical development, and the recent

changes in the supply and demand of scrap in these markets. The types of

ferrous scrap are related to their origins, availability, and extent of

present recycling. Ferrous scrap recovered from municipal solid waste, a

new source of ferrous scrap, is discussed in terms of the traditional

sources of scrap, its role as a major contributor to the supply of scrap,

and the effect of impediments to increased usage of this type of scrap.

Finally, it is necessary to establish some definitions of terms for this

discussion. Virgin or primary metals are produced from ores. Scrap or

secondary metals are derived from primary metals or previously fabricated

metal products. This scrap can be utilized in place of virgin metal or the

scrap can replace some other type of scrap in manufacturing a new product.

Ferrous Scrap History

Ferrous scrap is consumed by industries other than iron and steel

producers, iron foundries, and ferroalloy producers. The detinning

industry and the copper precipitation industry both use ferrous scrap which

has special characteristics appropriate for these two uses. In terms of

annual scrap consumption, however, iron and steel producers are the

dominant force in the ferrous scrap market as seen in Table 1.

In the iron and steel industry, the first efforts to make use of scrap

iron or ferrous scrap in the production of iron and steel were closely

1
associated with the development in the 1850’s of the first modern

steelmaking process, the acid-Bessemer process. In the early part of the

nineteenth century, steel was made by the crucible process with outputs of

about 45 kg per hour. The new Bessemer process could produce 4500 kg in

one-half hour so large scale production of steel was now possible. (5)

However, the acid-Bessemer process had two drawbacks which eventually led

to its 20th century demise. First, although the steel produced by this

process was suitable for many structural applications and the railroad

industry, the refining process in this air-blown furnace could not reduce

the phosphorus and nitrogen levels sufficiently to produce the high quality

steel needed by the automotive industry. Second, the acid-Bessemer furnace

could not accept more than about six percent ferrous scrap as part of the

furnace charge. This limited both the raw materials that could be used and

the grades of steel that could be produced. From the 1850 's on,

substantial amounts of scrap iron and steel accumulated from the expanding

iron and steel-making industry, fabricating operations, and worn out or

obsolete iron and steel products from the railroads and other industries.

This ferrous scrap, readily available and inexpensive, did not yet have a

market because of the absence of a steel refining process which could

consume substantial quantities of scrap.

In the 1860 's, Siemens invented the regenerative heating principle for

steelmaking which permitted heating solid pig iron, iron ore, and scrap to

high temperatures for refining and the modern open-hearth steelmaking

process was born. (5) The solid charge or feed stock for the open-hearth

could be all scrap and thus the open-hearth furnace had a considerably

greater capacity to consume ferrous scrap than the acid-lined Bessemer

furnace. Basic-lined open-hearth furnaces, which permitted control of the

2
sulfur and phosphorus content of steel, were first installed in the late

1880's, and were able to make use of the extensive U.S. iron ore deposits

whose phosphorus content was too high for the acid-Bessemer furnace.

Growth of the open-hearth process was rapid and by 1900 open-hearth steel

accounted for one-third of the U.S. steel production. By 1908, open-hearth

steel tonnage exceeded Bessemer steel production(6) and remained the

dominant steelmaking process in the U.S. until 1970. Thus, within twentyfive years of the development of modern steelmaking technology, a large

market for ferrous scrap was developed.

There have been two other modern steelmaking developments which have

had different impacts on the ferrous scrap industry. First, in 1878

Siemens built the first electric-arc furnace for making steel. Advantages

of this process were low capital costs per ton of capacity and a charge or

feedstock that was usually 100 percent solid iron or scrap, so molten pig

iron from a blast furnace was not needed. Until World War II, electric-arc

furnaces produced primarily tool steels, stainless steels, and other high

alloy steels in small furnaces ranging up to 18 metric tons in capacity and

had only a small impact on the ferrous scrap market. Electric furnace

steel production had grown so slowly that by 1955 it represented less than

seven percent of total steel production. In the years following World War

II, numerous large capacity furnaces, up to 360 metric tons in size, were

installed and many were used to produce the common carbon steel grades. As

a result, by 1969, electric furnace steel production increased to more than

14% of the annual steel production with a corresponding increase in scrap

consumption. (7) By 1978, electric furnace steel production accounted for

about 23% of the total U.S. steel production. (1)

The second development resulted in the re-birth of the pneumatic

Bessemer-type process. Although the early developers of pneumatic

3
steelmaking recognized the value of blowing oxygen instead of air to

oxidize impurities and adjust the steel chemistry, the technology for

producing large quantities of low cost oxygen was not available until after

World War II. Thus, the inability of air, containing about 80% nitrogen,

to refine steel to sufficiently low nitrogen levels combined with the

difficulty of removing phosphorus in the air-blown, acid-lined furnace,

resulted by 1950 in the decrease of Bessemer steel production to less than

five percent of the U.S. total production.

After World War II, conditions developed in Europe which required the

production of a low nitrogen steel. At that time, open-hearth scrap was

scarce, the available blast furnace pig iron was not chemically suitable

for the bottom-blown Bessemer furnace, and high purity, low cost oxygen was

available. A steelmaking process, known as the basic oxygen process or LD

process, was developed in Austria over the years 1949 to 1952 which used

top-blown oxygen instead of air as the oxidizing or fuel agent in a

basic-lined Bessemer-type furnace and consumed less scrap per furnace

charge than the open-hearth furnace. Steel low in phosphorus and nitrogen

could be produced more rapidly and at lower costs than in the open-hearth

furnace; the capital costs of these basic-oxygen furnaces (BOF) were lower

than new open-hearth construction. (6 , 8) By 1970, the production of BOF

steel surpassed open-hearth steel and became the dominant steelmaking

process in the U.S.

Iron foundries originally used hot metal from blast furnaces or

solidified pig iron as the primary charge in the cupola iron-making

furnace. (9) However, by the early 1950's, ferrous scrap had replaced about

40% of the cupola charge. Further, during the early 1960's, concurrent

with the growth in electric-arc steelmaking capacity, iron foundries also

4
added electric-arc furnaces for the production of cast iron. (3) By 1973,

electric-arc furnaces produced 23% of the cast iron while cupola furnace

production declined to 73%. (10) Total production of ferrous castings in

1979, including gray cast iron, ductile cast iron, and malleable cast iron,

totaled about 15.3 million metric tons with gray iron representing 72% or

about 11 million metric tons. (2) Over 90% of the furnace charge in the

gray cast iron industry is ferrous scrap.

The copper precipitation industry uses ferrous scrap for a

precipitating agent in processing low grade copper ores and mine tailings.

The copper-bearing material is dissolved in sulfuric acid to produce copper

sulfate. Light gauge ferrous scrap is added to the copper sulfate solution

causing the copper to be chemically displaced by the iron forming a copper

precipitate. The principal sources of the light gauge ferrous scrap are

the ferrous residue from the solid waste incinerators and detinned ferrous

scrap from the detinning industry, another consumer of ferrous scrap.

Detinners process only tin-plate scrap, usually from can manufacturers and

steel tin-plate mills, in order to reclaim the tin and as a by-product

generate a high quality "tin-free" ferrous scrap which can be consumed

directly by the iron and steel industry as well as by the copper

precipitation industry. (The secondary metals industry designation for

this detinned can scrap is No. 1 bundles.) In the detinning process, the

tin coating is dissolved in hot sodium hydroxide. The tin is then electrolytically precipitated from the sodium stannate solution.

Sources of Ferrous Scrap

Traditionally, ferrous scrap has been called either home scrap, prompt

industrial scrap, or old scrap. Home scrap, or revert scrap, generated

during the production of steel or cast iron, is always recycled because its

5
history and chemistry are well known. Manufacturing industries also

produce scrap during the fabrication of various industrial, commercial, or

consumer steel products. This scrap called prompt industrial scrap or new

scrap, is also widely recycled because its chemical and physical

characteristics can be well documented, although in some cases, additional

processing such as detinning or compacting must be carried out to put the

scrap in a form suitable for recycling. The availability of prompt

industrial scrap is directly related to the level of industrial economic

activity. Prompt industrial scrap producers usually cannot allow it to

accumulate because of storage requirements and costs of inventory control.

Thus, it is rapidly available at current prices to the steelmaker or

ferrous scrap industry.

All other ferrous scrap is included in the third category called old

scrap, obsolete scrap, or post-consumer scrap. This category includes all

goods or products in which the iron content can at least in theory be

recovered and recycled. The major types of old scrap recycled in the

United States are railroad, machinery, and automotive while in foreign

countries with lower labor costs, shipbreaking is a major source of

obsolete scrap. Although automotive scrap, that is, recycled automobiles,

has been a traditional source of obsolete scrap, advances in recycling

technology during the early 1960's greatly enhanced the value and

importance of this ferrous scrap. Ferrous scrap recovered from municipal

solid waste (MSW) , sometimes called MSW magnetics or municipal ferrous

scrap (MFS), is a new non-traditional source of obsolete scrap. In terms

of quality, desirability, and cost, home scrap generally ranks highest;

prompt industrial scrap second; and old scrap, including municipal ferrous

scrap last. This lower ranking of old scrap is a direct consequence of its

6
greater heterogeneity in chemical and physical characteristics making it

more costly to process.

Recent estimates (9 , 11 , 12) suggest that from 9 to 11 million metric

tons per year of ferrous scrap are discarded into municipal solid waste and

yet less than two percent, i.e. 450,000 metric tons has ever been recovered

in any year. In 1979, about 180,000 metric tons of municipal ferrous scrap

was recovered. (13) Although the composition of municipal solid waste

exhibits regional, seasonal, and other variations, some broad ranges for

important components have been identified as shown in Table 3. Overall,

approximately 80% of MSW is combustible, including about 20% moisture.

Ferrous scrap accounts for about 85% of the noncombustibles. Beverage and

food cans, (excluding all-aluminum cans), make up between 50% and 90% of

the ferrous fraction in municipal solid waste.

Role of Ferrous Scrap in Modern Steelmaking Processes

Modern steelmaking processes can be divided into two categories based

on materials flow. One category contains the blast furnace together with

the open-hearth and/or BOF refining furnaces, and the second category

contains, the electric refining furnaces.

In an integrated steel mill, where iron ore is converted into finished

steel products, the ore is chemically reduced with coke and limestone in a

blast furnace to molten pig iron or hot-metal. The hot metal is combined

with ferrous scrap in an open-hearth furnace or a BOF and refined until the

desired grade of steel is produced. The open-hearth furnace has the

greatest flexibility in its consumption of scrap because a portion of the

heat needed to melt the scrap is supplied by an external fuel. It can

process 100% hot metal, 100% scrap or solid pig iron or any combination

in-between. Usually 40% to 60% scrap is charged with hot metal. However,

7
the importance of the open-hearth process is rapidly declining so its scrap

flexibility is being lost. Scrap usage in the BOF is limited because the

oxidation of carbon and silicon is the only source of heat for melting the

scrap. Without preheating, the maximum amount of scrap per charge consumed

in the BOF is about 33%.

The electric-arc furnace, like the open-hearth furnace, refines a

material charge with any ratio of hot metal to solid metal, but typically

operates with a solid charge of almost all scrap. The rapid increase in

electric furnace capacity in the last two decades has been paced by the

growth of mini-mills, small capacity steel mills using only electric-arc

furnaces based on 100 percent scrap, and expansion of electric-arc furnace

capacity by integrated steel mills producing carbon steels. Mini-mills

have greater geographic independence than integrated steel mills because

they are not dependent on sources of iron ore, coke, and limestone. Thus,

mini-mills often produce steel products for local or regional markets and

can adapt more readily to changes in the steel market. Some integrated

steel mills have also substantially increased electric-arc steel production

when hot. metal shortages developed as a result of the use of BOF units with

their higher consumption of hot metal. In addition, the high cost per ton

of annual capacity of constructing a new or "greenfield" integrated steel

mill, which includes coke ovens, blast furnaces, and BOFs, has limited the

options available for increasing steelmaking capacity. Growth in electric

furnace capacity has led to increased demand for ferrous scrap.

According to Table 4, steel industry data for 1978 show that the basic

oxygen furnaces produced about 61% of domestic steel, electric-arc furnaces

about 23%, and open-hearth furnaces about 16%. (1) However, about 49% of

the total ferrous scrap consumed went to electric-arc furnaces, 34% to the

8
BOF, and almost 17% to open-hearth furnaces. Over 52% of the total steel

production was from ferrous scrap. By 1988, the steel industry forecasts

the demise of the open-hearth furnace process with both its capacity and

any additional growth in steel production being met by the BOF and

electric-arc furnaces. The BOF will be expected to account for about 68%

of the total steel production and electric-arc furnaces the remaining 32%.

In terms of ferrous scrap consumption, however, electric-arc furnaces will

use 65% of the total scrap and the BOF will use only 35%. It should be

noted that in 1978, 1.31 metric tons of scrap were consumed by electric-arc

furnaces for every ton of scrap used by the basic oxygen furnaces, while

the forecast for 1988 shows 1.69 metric tons of scrap used by electric-arc

furnaces per ton of scrap used by the BOF. Thus, the growth in scrap

consumption will occur primarily through growth in electric-arc furnace

capacity. Further, as open-hearth capacity decreases, additional hot-metal

capacity will be freed to supply the BOF. Thus BOF scrap usage as a

percent of the charge may fall slightly.

Historically, significant changes in the primary steelmaking processes

have strongly affected the role of ferrous scrap in modern steelmaking

technology because of the key part played by ferrous scrap as a source of

iron. The rapid displacement of the open-hearth furnace by the BOF from

1956 to 1970 increased the demand for hot metal and reduced the demand for

obsolete scrap. The reduced scrap needs in the BOF were more easily met by

the supply of home scrap and prompt industrial scrap. This transition from

open-hearth dominance to BOF dominance was accompanied by an increase in

the cost of molten pig iron and a decrease in the cost of ferrous

scrap. (15) The availability of lower cost scrap was a main contributing

9
factor to almost doubling electric-furnace steel production, especially for

carbon steel grades, from 1956 to 1970.

Typically, rising steel production increases the demand and cost of

scrap and vice versa when steel production falls. The supply of prompt

industrial scrap, however, is not strongly related to scrap prices but,

rather, is closely related to the level of steel consumption. The supply

of obsolete scrap, on the other hand, is more closely tied to scrap prices.

A study from 1950 to 1973 concluded that over the short term, the supply of

obsolete scrap was directly proportional to the price. (16) The price of

ferrous scrap is highly volatile. Contributing to this instability in the

short term are several characteristics of typical scrap purchase

agreements . (10) Ferrous scrap usually is purchased on the basis of 30 day

or 60 day delivery contracts so that short term changes in steel production

directly impact the demand for scrap. Further, the basis for acceptance in

terms of quality control is often not consistent so that scrap buyers can

hedge against short term decreases in price at the time of delivery by

rejecting the scrap shipment based on quality. The weekly composite price

per metric ton for the largest tonnage grade of ferrous scrap reflects

these price fluctuations, shown in Figure 1 for the past four years. The

maximum price change as a percent of the annual low price was 56% for 1977,

23% for 1978, 48% for 1979, 57% for 1980, and 38% for 1981.(17) Long term

effects on the price of scrap include international demand and technology

changes that affect both scrap sellers (auto shredders) and scrap buyers

(electric furnaces). Since 1970, changes in the scrap market occurred which

have led to some recent anomalies in the domestic supply-demand

relationship for ferrous scrap.

10
Excess scrap accumulated during periods of low steel production is

consumed during high demand years. Low ferrous scrap consumption during

1971 and 1972 generated a scrap inventory that supplied the strong domestic

and export demand for scrap in 1973 with only small price increases. In

1974 rapid increases in scrap prices occurred because of dwindling

inventories. Again, reduced scrap consumption in 1976 and 1977 provided a

supply of scrap that satisfied the high demand for scrap, particularly for

export, during 1979 and 1980. However, during two periods in the years

1979 and 1980, scrap prices rose substantially at the same time domestic

scrap demand decreased. One factor contributing to the unusual behavior

was the increased export demand for scrap. From 1978 to 1980, about 9

million metric tons of scrap was exported each year, while the average for

the previous ten years was about 7.5 million metric tons per year, or 20%

less. Another explanation, one favored by steel industry consumers of

scrap, is the belief that the demand for obsolete scrap exceeds and will

continue to exceed the supply that is economically available. (18) This

demand is attributed to increases in the number of mini-mills; expansion of

electric-furnace capacity by domestic integrated steel producers; increased

electric-arc furnaces capacity by foreign steelmakers thus increasing the

number of foreign countries buying U.S. scrap. The position of the

secondary metals industry is that the continued high demand and high price

for scrap will in the long run result in an increased recovery of obsolete

scrap, and that the present domestic inventory of obsolete scrap is more

than sufficient to meet the future needs of both the domestic and the

export scrap markets. The potential market for new sources of obsolete

scrap, including municipal ferrous scrap, includes therefore not only

domestic markets but also a growing export market.

11
Recycling Ferrous Scrap from Municipal Solid Waste

The development in the 1960s of a national interest in recovery of

various materials including ferrous scrap from municipal solid waste,

resource recovery, was a response to increasing solid waste disposal

problems. (12) Some communities were running out of landfill capacity.

Traditional solid waste incineration was declining due to air pollution

control regulations. Many existing sanitary landfills were not "sanitary"

and were being closed. New landfill sites were becoming more difficult to

locate because of land availability or the inability of proposed sites to

satisfy health and safety regulations. Thus, the incentive for the

development of a resource recovery industry generating ferrous scrap as one

of many products was different from the forces which created a secondary

metals industry marketing ferrous scrap from traditional sources. Resource

recovery offered the opportunity to achieve a significant reduction in the

volume of municipal solid waste. Raw solid waste could be separated into

glass, ferrous, aluminum, and the organic or combustible fractions; a

process called front-end separation. The sale of the materials would

provide income to help offset separation costs and disposal of the

unsalable residue. Recycling of ferrous scrap from municipal solid waste

cannot be a major materials supplier because the quantities of ferrous

scrap cannot provide enough material to satisfy annual consumption.

However, municipal ferrous scrap has the potential to supply up to 10% of

the nation’s annual scrap consumption.

A more recent incentive for recycling can be traced to the oil embargo

in the early 1970s and the emphasis on energy conservation and development

of alternative energy sources. The combustible fraction in municipal solid

12
waste is receiving considerable attention as either a supplementary boiler

fuel or as the only fuel in mass-burning facilities for the generation of

steam and/or electricity. Ferrous scrap and other non-combustible

materials can be removed from the solid waste as the waste is processed

into a form suitable for a fuel, or if the unseparated solid waste is used

as the fuel, the ferrous scrap can be separated and recovered from the

boiler ash.

Finally, economic value and/or ease of recovery can be strong

motivating factors for recycling a particular material. Many metals,

including tin, aluminum, copper, lead, zinc, nickel, and iron, are recycled

because of their high economic value per unit weight or volume. Some of

these metals have physical characteristics such as high density or

magnetism which permit mechanical separation, while other metals have

chemical characteristics such as ease of selective dissolution which

facilitate chemical separation. The cost of separation and recovery by

mechanical systems is usually lower than for chemical systems. (12)

Further, ferrous materials are among the easiest to recover because iron

and most steels (excluding certain grades of stainless steel) are

ferromagnetic and can be routinely separated from non-magnetic materials

using standard industrial drum or belt magnetic separators with either

permanent magnets or electromagnets . (19)

A number of systems have been developed to process municipal solid

waste in order to separate and recover the materials of interest. The

principal unit operations for separating municipal ferrous scrap include:

(a) incineration or mass-burning of the solid waste followed by magnetic

separation of the ferrous residue from the ash; (b) front-end separation

13
or shredding the solid waste followed by magnetic separation and/or air

classification; and (c) wet pulping. (20)

Most facilities currently operating use either approach (a) or (b)

,

although a single system combining shredding and the separation of the

non-combustibles followed by mass burning to generate steam and/or

electricity probably combines the best technical features of both

systems. (11) Since each unit operation sequence affects the chemical and

physical characteristics of the recovered ferrous scrap differently, the

relationship between processing, contamination and market will vary.

Impediments to Increased Usage of Municipal Ferrous Scrap

There are a number of factors that promote the separation and recovery

of municipal ferrous scrap from solid waste. These include: increasing

domestic demand for old scrap due to the growth of electric furnace

capacity and increased exports; generation of ferrous scrap as a by-product

of burning municipal solid waste as a fuel; the relative ease of separating

and recovering ferrous scrap from the other constituents in municipal solid

waste; and pressure for increased recycling as part of an overall materials

conservation effort. Yet, in spite of these inducements, significant

growth in the demand for municipal ferrous scrap has not yet occurred. In

fact, market consumption of municipal ferrous scrap has actually decreased

since 1976.(21) At the end of 1979, there were 56 municipal resource

recovery systems in operation, but only 27 were actually separating and

recovering ferrous scrap. (13)

The obstacles to increased consumption of municipal ferrous scrap are

usually divided into two categories, institutional and technical. Both

of these barriers have an impact on the economics of recycling municipal

ferrous scrap or cost of producing the scrap, while the elimination of only

14
one barrier is a necessary but not sufficient condition for increased

usage. Many institutional barriers to recycling MSW have been identified

in recent years. (10,22,23) . These include: the effect of depletion

allowance taxes and severance taxes; the effect in the past of different

transportation tariffs for virgin ores and secondary materials; ownership

and control of the flow of municipal solid waste; public sector versus

private sector ownership and operation of resource recovery facilities; and

control of ferrous scrap exports. These and other institutional barriers

will not be further discussed because often the obstacles are artificial or

arbitrary and almost all contain significant questions of public policy.

However, if these institutional obstacles were eliminated, technical

barriers would remain which are equally important in limiting the demand

for municipal ferrous scrap.

The technical barriers are primarily of two types: lack of national

standards and specifications for the materials recovered from municipal

solid waste(12); and true technological obstacles resulting from the impact

of municipal ferrous scrap on processes using this material and the

properties and quality of products made with the material. Lack of

national material specifications and standard test methods for recovered

materials place the producer of recovered products, such as a resource

recovery facility, at a disadvantage with regard to identifying which of

the potentially recoverable materials have real markets and which materials

do not.

The primary technical obstacle limiting demand for scrap, and in

particular municipal ferrous scrap, is the presence in the scrap of certain

chemical impurities or residual elements, primarily tin, copper and

aluminum, in amounts in excess of that found in either home or prompt

13
industrial scrap or in primary metal produced from virgin ore. In the iron

and steel industry and iron foundry industry, the levels of residual or

tramp elements can seriously impair the properties of steel and cast iron

products made with this scrap. In the detinning industry, copper

precipitation industry and in iron and steel production, these residual

elements can also disrupt the chemical processes themselves. In MFS, the

tin originates primarily from tin-coated food and beverage cans while the

aluminum contamination arises from the aluminum tops of bi-metal beverage

cans. Copper is contributed by electrical components such as motors and

wire although increased copper contamination occurs in the metallic residue

of incinerators or mass-burning plants due to the vapor deposition of

copper onto the residue. (14) Municipal ferrous scrap as produced by a

single magnetic separation operation will almost always exhibit a high

level of contamination not only by tramp elements but also by organic

materials which have been carried along through attachment or association

with the magnetic material. Although municipal ferrous scrap in this form

can be used in each of the five major scrap consuming industries, these

levels of contamination severely limit the amount of this scrap that can be

used. For example, this MFS is limited in the iron and steel

industry (12 ,24) and iron foundries(14) , to about 10% of the respective

furnace scrap charges.

Markets for Municipal Ferrous Scrap

If substantial growth in the domestic consumption of municipal ferrous

scrap is to occur, it must take place in the iron and steel industry and

the iron foundry industry which together currently account for about 97% of

the total scrap consumed, as seen in Table 1.

16
Iron and Steel Production

Municipal ferrous scrap can be charged to either the blast furnace

producing hot metal or to the BOF or electric-arc steelmaking furnaces.

Charging municipal ferrous scrap as part of the electric furnace or BOF

charge (without preheating) merely displaces another type of scrap and does

not result in increased scrap consumption. Only if more steelmaking

furnaces are built could scrap usage increase. True recycling can occur if

municipal ferrous scrap is charged to the blast furnace because the scrap

will displace iron ore, a virgin material. Increased scrap consumption

would result even if overall iron and steel production did not increase.

Studies have shown that the iron content in 32 kg of ore could be replaced

by 23 kg of scrap . (25 , 26) In either case, however, the tramp elements tin

and copper are not removed in either the blast furnace or the steel

refining furnace. Although quantitative upper limits on copper and tin

content for particular grades of steel are not always known, studies have

shown that copper and tin increase susceptibility to surface melting or hot

shortness during hot rolling operations and embrittlement at high

temperatures, and decrease tensile ductility and toughness; all undesirable

effects. Data reported for front-end separated scrap and incinerator

residue, shown in Table 5, illustrates the magnitude of the problem.

Although the aluminum content of municipal ferrous scrap varies widely

depending on the fraction of bi-metallic cans present, an upper limit of 2%

can be estimated based on available data. (27) When this scrap is charged

in a blast furnace, the aluminum will exothermically reduce some of the

iron oxide from the ore charge to form alumina. The combination of

increased temperature and alumina will decrease the life of the blast

furnace lining. Using this scrap in a steelmaking furnace creates somewhat

17
different problems. Here the aluminum reacts with the iron oxide in the

slag and alters the slag chemistry. As the iron oxide content of the slag

decreases, phosphorus reversion in the slag occurs and the phosphorus level

in the steel increases, decreasing the formability of the steel.

Processing the waste can reduce the detrimental effects of these tramp

elements. Shredding the solid waste followed by air classification will

greatly reduce the organic contamination by removing most of the light

paper and plastics (19) , and if the ferrous fraction is then magnetically

separated, the copper level will be greatly reduced(14) because the

non-magnetic copper constituents are left behind. A second finer shredding

and a second magnetic separation can reduce the aluminum by up to one third

because many of the aluminum can tops become separated from the can

bodies(30) and are left behind. Alternatively, heating the scrap to 600 F

(315°C) oxidizes the aluminum and reduces the aluminum level by 70%. (31)

At this point the tin level can be reduced to the range 0.03% to

0.1%(32,33) by chemical detinning, producing a material which approaches

the quality of No. 1 bundles. (34)

Iron Foundries

The tramp elements tin and aluminum and to a lesser extent copper also

affect the properties and structure of the various cast irons produced,

including gray cast iron, ductile cast iron, and malleable cast

iron. (24,25) The aluminum concentration is sufficient to cause casting

problems. Excessive slag formation can occur as the aluminum is oxidized

to alumina; but, more importantly, the presence of as little as 0.02%

aluminum increases the susceptibility to pinhole formation or porosity due

to hydrogen absorption from the air or from moisture in the mold. In cast

iron, tin levels above 0.04% completely stabilize the pearlitic

18
microstructure and thus changes the properties. For ferritic ductile iron

grades, the maximum tin level should be lower than 0.04% and for unannealed

malleable cast iron, the upper limit is about 0.02%(28). Copper up to 0.5%

reduces the ductility of ductile cast iron. Trial cupola heats using 10%

of the charge as undetinned magnetically separated municipal ferrous scrap

produced satisfactory gray cast iron automotive castings. (35) Although

cast irons are more tolerant of some tramp elements than steel, processing

operations similar to those identified for upgrading municipal ferrous

scrap for iron and steel production would be needed to lower the tin and

aluminum levels before significantly higher proportions of this scrap could

be routinely used in foundries.

Ferroalloy Production

Ferroalloys, used as additions in the production of alloy steels, are

made primarily in electric-arc furnaces. Municipal ferrous scrap has been

used as part of the furnace charge for producing ferroalloys even though

alloy steels often have greater limitations on tramp element levels than

the carbon steels. Incinerator scrap is preferred because all of the

organic contaminants have been eliminated, even though significant tin and

copper impurities from the scrap ultimately end up in the alloy steel

product. However, since the ferroalloy is typically only a small addition

to the steelmaking furnace, the dilution of the tin and copper results in

acceptable levels in the steel product. (28)

I Detinning and Copper Precipitation

The detinning industry produces the only domestic supply of tin and

uses clean tin-plate scrap as the source of tin. Municipal ferrous scrap

with its high percentage of tin-coated food and beverage cans is another

! potential tin source. Bi-metallic cans with aluminum tops and possibly

19

I
organic contaminants, however, pose severe problems in the commercial

detinning process. The sodium hydroxide solution used to dissolve the tin

will react with the aluminum to form sodium aluminate, thus consuming the

detinning reagent. The sodium aluminate further causes an increased loss

of solution when the detinned material is removed from the bath due to

increased solution viscosity (24) , and reduces the efficiency of the

electrodeposition process which recovers the tin from the bath(12).

Although aluminum contamination can be considered an economic problem as

well as a technical obstacle, the impact is continuous, with no minimum

threshold, and of magnitude directly proportional to the aluminum

content. (31) The organic contaminants, including textiles and food residue

retained in the cans, are retained in the sodium hydroxide solution and

thus interfere with the optimum operation of the bath. Additional

processing of municipal ferrous scrap, such as a second shredding and

second magnetic separation or a chemical pre-treatment , is often necessary

to reduce the aluminum and organic contamination to acceptable levels.

The primary requirement for municipal ferrous scrap use in the copper

precipitation industry is a high surface area to volume ratio and a low

level of organic contamination. Although detinned municipal ferrous scrap

is more chemically reactive in the precipitation reaction than incinerated

scrap where the tin is alloyed with the iron, both types of scrap are

essentially free of organics and are used to recover copper. In 1974,

almost 15% of the domestic copper production was produced by the

precipitation process. (4) Further expansion of this market is uncertain

because of a trend towards using ion-exchange techniques to recover the

copper . (36)

20
Role of Standards

There is a consensus that the development and operation of resource

recovery systems has been hindered by the absence of widely accepted

national standards and specifications applicable to materials recovered

from municipal solid waste. (12,37,38) The first codification of ferrous

scrap specifications occurred in 1926.(39) These specifications and their

modern successors are "origin specifications" which describe the source of

the material and the limits of the major contaminants. Origin

specifications are most successful when the materials are derived from

established processes . (38) The principal focus in the past has been on

industrial scrap and certain special categories of obsolete scrap such as

V railroad products and automobiles in which the scrap can be characterized

using origin specifications.

There is a strong need for quantitative specifications for materials

recovered from municipal solid waste. Although the value of recovered

materials generally increases with purity and homogeneity, the key to the

usefulness of these materials, and thus their potential for increased

markets, is the ability to ensure a reproducible quality. (12) Often it is

the uncertainty over impurity content that causes potential buyers of

recycled materials to fall back and demand unnecessary higher levels of

scrap quality. Acceptability of materials recovered from solid waste is

the major problem. It is necessary to overcome the garbage syndrome—if it

looks like garbage, feels like garbage, smells like garbage, then it must

be garbage.

Recognition of this problem in 1974 led the American Society for

Testing and Materials (ASTM) to create Committee E38 on Resource Recovery

to bring together representatives of many diverse interests in this new

21
field for the purpose of developing standards. An important goal of this

process of developing consensus standards was to insure significant

participation by all interested parties, especially the intended users of

these standards, so that a strong incentive is created to apply the

standards in the market place. Representatives of resource recovery

facilities, Federal and state agencies, and industrial consumers of ferrous

scrap, working in cooperation, have developed two national consensus

standards for municipal ferrous scrap that have been formally adopted by

ASTM: ASTM E701-80, Standard Methods of Test for Municipal Ferrous Scrap;

and ASTM E702-79, Standard Specification for Municipal Ferrous Scrap. (40)

The specification document defines the chemical and physical requirements

for municipal ferrous scrap in the five market areas of copper

precipitation, iron foundries, iron and steel production, detinning, and

ferroalloys. Requirements for chemical composition, metallic yield,

cleanliness as measured by combustibles content, and bulk density are

listed where applicable. Footnotes giving processing hints and limitations

have been added to provide supplementary information for those not

experienced in the resource recovery business.

Trends

Present trends in steelmaking technology and ferrous scrap

supply (9, 41) could result in increased demand for scrap including municipal

ferrous scrap. The reduced size of automobiles will eventually reduce the

supply of automotive scrap while changes in materials used in automobiles

may lower the resulting scrap quality. Anticipated growth in continuous

casting capacity with its lower scrap generation than ingot casting, and

improved electric furnace productivity will reduce the quantity of home

22
scrap. Efforts by some steel fabricators to recycle their in-house scrap

will reduce the availability of prompt industrial scrap. Finally, the

continued growth of scrap-based electric-arc furnace capacity, combined

with increasing overseas exports of scrap, will place added pressures on

additional sources of scrap.

23
REFERENCES

1. "Steel at the Crossroads: The American Steel Industry in the 1980's,

American Iron and Steel Institute, Washington, D.C., (1980).

2. "1980 U. S. Industrial Outlook", U. S. Department of Commerce,

Industry and Trade Administration, (1980).

3. "Ferrous Scrap", Journal of Metals, Vol. 26, 33-40, (1974).

4. "Progress Report on Recycling", Tin Mill Products Producers, American

Iron and Steel Institute, (1974).

5. L. F. Reinartz, "Steelmaking/USA Part I, History of Iron and

Steelmaking in the United States," Metallurgical Society, American

Institute of Mining, Metallurgical, and Petroleum Engineers, New York,

N.Y., 73-76, (1961).

6. A. B. Wilder, "One Hundred Years of Bessemer Steelmaking, History of

Iron and Steelmaking in the United States", Metallurgical Society,

American Institute of Mining, Metallurgical, and Petroleum Engineers,

New York, N.Y., 61-72, (1961).

7. S. B. Casey, "The First Half-Century of Electric Furnace Steel Making,

History of Iron and Steelmaking in the United States", Metallurgical

Society, American Institute of Mining, Metallurgical, and Petroleum

Engineers, New York, N.Y., 92-95, (1961).

8. "The Pneumatic Steelmaking Processes", The Making, Shaping, and

Treating of Steel, H. E. McGannon, Editor, 9th Edition, United States

Steel Corporation, Pittsburgh, PA, 486-497, (1971).

9. M. B. Bever, "The Recycling of Metals-I. Ferrous Metals",

Conservation and Recycling, Vol. 1, 55-69, (1976).

10. J. A. Commins, V. A. Hathaway, E. F. Palermo, B. M. Sattin, and M. A.

Timothy, "Barriers to the Use of Secondary Metals", U. S. Bureau of

Mines Report, NTIS PB 271 814, (1977).

11. J. G. Abert, "State and Tendencies of Recycling in North America",

International Recycling Congress, Berlin 1979, K. J. Thome-Kozmiensky

,

Editor, 18-27, (1979).

12. "Mineral Resources and the Environment, Supplementary Report:

Resource Recovery from Municipal Solid Wastes", National Academy of

Sciences, Washington, D.C., (1975).

13. "Summary Report of Solid Waste Processing Facilities", Committee of

Tin Mill Products Producers, American Iron and Steel Institute,

Washington, D.C., (1978).

14. E. J. Ostrowski, "Recovery and Use of Ferrous Scrap from Municipal

Refuse", Transactions American Foundrymans Society, 111-116, (1977).

24
15. D. J. Carney, "Electric Furnace Steelmaking in the Next Decade",

Journal of Metals, Vol. 26, 41-51, (1974).

16. H. B. Jensen, "Analysis of Ferrous Scrap Supply/Demand Balance USA",

Electric Furnace Proceedings, Metallurgical Society of the American

Institute of Mining, Metallurgical and Petroleum Engineers, Vol. 30,

(1973).

17. American Metal Market/Metalworking News, October 13, 1980 and

September 14, 1981.

18. H. B. Jensen, "A Changing U.S. Scrap Market", American Society for

Metals Materials and Processes Congress, Cleveland, Ohio, (October 28,

1980).

19. H. Alter and K. Woodruff, "Magnetic Separation: Recovery of Salable

Iron and Steel from Municipal Solid Waste", U.S. Environmental

Protection Agency Report EPA/530/SW-559, (1977).

20. N. T. Neff, "Solid Waste and Fiber Recovery Demonstration Plant for

the City of Franklin, Ohio", U.S. Environmental Protection Agency

Report, NTIS PB 213 646, (1972).

21. "Drop in Steel Demand puts Damper on Ferrous Metal Recovery From

Waste", Solid Waste Systems, 10-13, (1978).

22. J. G. Abert, "Procurement and Contracting", Resource Recovery and

Utilization, American Society for Testing and Materials STP 592,

31-39, (1975).

23. J. N. Humber, "Management, Marketing, Financial, and Legal Issues",

Resource Recovery and Utilization, American Society for Testing and

Materials STP 592, 40-52, (1975).

24. R. S. Kaplan, "Deterrents to the Recycling of Ferrous Scrap from Urban

Refuse", Resource Recovery and Utilization, American Society for

Testing and Materials STP 592, 91-105, (1975).

25. E. J. Ostrowski, "Technical Considerations for the Recovery of Solid

Waste Scrap in Blast Furnaces", Proceedings Ironmaking Conference,

American Institute of Mining, Metallurgical, and Petroleum Engineers,

Vol. 30, 115-124, (1971).

26. E. J. Ostrowski, "Recycling of Solid Ferrous Scrap in the Blast

Furnace", Annual Mining Symposium of Minnesota Section, American

Institute of Mining, Metallurgical, and Petroleum Engineers, (1974).

27. H. V. Makar, et al. , "Evaluation of Steel Made with Ferrous Fractions

of Urban Refuse", U.S. Bureau of Mines Report RI-8037, (1975).

28. E. J. Duckett, "The Influence of Tin Content on the Reuse of Magnetic

Metals Recovered from Municipal Solid Waste", Resource Recovery and

Conservation, Vol. 2, 301-328, (1976/1977).

25
29. E. J. Ostrowski, Private Communication.

30. E. J. Ostrowski, "Recycling of Tin Free Steel Cans, Tin Cans and Scrap

from Municipal Incinerator Residue", 79th General Meeting of the

American Iron and Steel Institute, New York, N.Y. , (1971).

31. E. J. Duckett, "Contaminants of Magnetic Metals Recovered from

Municipal Solid Waste", National Center for Resource Recovery Report

NSF/RA-770244 , Washington, D.C., (1977).

32. W. L. Hunter, "Steel from Urban Waste", U.S. Bureau of Mines Report

No. 8147, (1976).

33. P. M. Sullivan and H. V. Makar, "Quality of Products from Bureau of

Mines Resources Recovery Systems and Suitability for Recycling",

Proceedings Fifth Mineral Waste Utilization Symposium, U.S. Bureau of

Mines and IIT Research Institute (1976).

34. "Scrap Studies Could Aid Mills", Metalworking News, Steelmaking Today

Supplement, (September 8, 1980).

35. R. C. Helmink, G. F. Ruff, and J. F. Wallace, "Ferrous Metal from

Municipal Wastes as Charge Material for Cast Iron", Transactions

American Foundrymans Society, (1974).

36. "Soft Market Slows Scrap Can Buying", Metalworking News, (August 14,

1978)

.

37. C. G. Interrante, "Report on the Ferrous Metals Workshop", Resource

Recovery and Utilization, American Society for Testing and Materials

STP 592, 146-152, (1975).

38. H. Alter, "Needed: Standards for Resource Recovery", American Society

for Testing and Materials, Standardization News, 11-13, (November

1979)

.

39. "Specifications for Iron and Steel Scrap", Institute of Scrap Iron and

Steel, (1971).

40. "General Test Methods, Nonmetal; Statistical Methods; Space

Simulation; Particle Size Measurements; Laboratory Apparatus;

Durability of Nonmetallic Materials; Metric Practice", 1981, Annual

Book of ASTM Standards, Part 41, 1022-1029, 1981.

41. "Some Shortage of Ferrous Seen by '85", Metalworking News, (February

25, 1980).

26
Table 1. Total Ferrous Scrap Consumption by Industry

Industry Year

Iron & Steel Production 1978

Iron Foundries 1979

Ferroalloy 1973

Detinning 1974

Copper Precipitation 1974

Metric Tons

Consumed Reference

66 x 10

6

(1)

13.6 x 10

6

(2)

0.45 x 10

6

(3)

0.64 x 10^ (a) (4)

0.45 x 10

6

(4)

(a) Based on 4.5 kg of tin per metric ton of

tin-plate scrap

27
Table 2. Modern Steelmaking Processes

Percent of U. S. Steel Production

Year Bessemer Open-hearth Electric-arc B0F

1890

(a) 86% 12% 0 0

1900 66% 34% 0 0

1907 50% 50% <1% 0

1950 5% 89% 6% 0

1969 <1% 43% 14% 43%

1978 <1% 16% 24% 60%

( 3- )' 2% produced by crucible process

References (1,5, 6, 7, 8)

28
Table 3. Typical Composition of Municipal Solid Waste, By Weight

paper and paper products

yard waste

food waste

plastics, textiles, rubber, wood

glass

metal

30% to 34%

20% to 21%

14% to 19%

4% to 12%

8% to 10%

8% to 10%

References (11,12,14)

29
Table 4. Steel Production and Scrap Consumption in the U.S

Basic Oxygen Electric--Arc Open-Hearth

Furnace (BOF) Furnace Furnace

Scrap Steel Scrap Steel Scrap Steel

Consumed Produced Consumed Produced Consumed Produced

Year metric tons

1978 23 x 10

6

77 x 10

6

32 x 10

6

30 x 10

6

11 x 10

6

20 x 10

6

1988 26 x 10

6

97 x 10

6

49 x 10

6

46 x 10

6

(Proj ected)

Reference (1)

30
Table 5. Tramp Element Levels in Municipal Ferrous Scrap

Tramp

Element

Typical

Tolerance Limit,

max

Municipal

Front-End

Separated

Ferrous Scrap

Incinerator

Residue

Tin 0.03 0. 5

<« 0.18

Copper 0.01 0.21

(c) 0.62

(a) Reference (27)

Reference (28)

(c) Reference (29)

i

i

31
NBS-H4A IREV. 2-801 U.S. DEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. Report No. 3. Publication Date BIBLIOGRAPHIC DATA

REPORT NO.

SHEET (See Instructions) NBSIR 82-2571 September 1982

4 . TITLE AND SUBTITLE

RECYCLING MUNICIPAL FERROUS SCRAP

5. AUTHOR(S)

James G. Early

6. PERFORMING ORGANIZATION (If joint or other than N BS, see in structlon s) national bureau of standards

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8 . Type of Report & Period Covered

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. Stale, ZIP)

10.

SUPPLEMENTARY NOTES

[ | Document describes a computer program; SF-185, FIPS Software Summary, Is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant in formation. If document includes a significant

bi bliography or literature survey, mention it here)

The secondary metals industry associated with the recycling of ferrous scrap is

tied to the development in the 1850's of the acid-Bessemer furnace, the first large

capacity steelmaking process. Within twenty-five years of this development, the

recycling of ferrous scrap became an established industry. Changes in steelmaking

technology since World War II, especially since the 1960’s, are impacting the

traditional ferrous scrap industry. The increased demand for old scrap is due to

growth in electric-arc furnace steelmaking capacity, reduced availability of home scraj

and prompt industrial scrap, and larger scrap exports. Ferrous scrap recovered from

municipal solid waste is one of the new sources of old scrap that may satisfy these

increased demands. Systems for the recovery of the ferrous fraction from municipal

solid waste have been developed, although increased usage of municipal ferrous scrap

has been very slow due to institutional and technical barriers. The technical barrier:

posed by the physical and chemical characteristics of municipal ferrous scrap strongly

inhibit the development of markets for this new material. The real and potential

markets for increased consumption of municipal ferrous scrap are discussed in terms of

these barriers together with the important role of standards for municipal ferrous

scrap in improving communications between buyers and sellers.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper nomes; and separate key words by semicolon s) Ferrous scrap; iron; municipal ferrous scrap; municipal solid waste; recycling

resource recovery; standards; steel

13. AVAILABILITY

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