TECHNICAL PAPER # 10
SCRAP METAL RECYCLING
VOLUNTEERS IN TECHNICAL ASSISTANCE
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Understanding Scrap Metal Recycling
Volunteers in Technical Assistance
This paper is one of a series publisher by Volunteers in
Assistance to provide an introduction to specific
technologies of interest to people in developing countries.
The papers are intended to be used as guidelines to help
people choose technologies that are suitable to their
They are not intended to provide construction or
details. People are urged to contact VITA or a similar
for further information and technical assistance if they
find that a particular technology seems to meet their needs.
The papers in the series were written, reviewed, and
almost entirely by VITA Volunteer technical experts on a
voluntary basis. Some 500 volunteers were involved in the
of the first 100 titles issued, contributing approximately
5,000 hours of their time. VITA staff included Leslie
and Maria Giannuzzi as editors, Julie Berman handling
and layout, and Margaret Crouch as project manager.
VITA Volunteer Jon Vogler, the author of this paper, is
published in the field of recycling. His book Work From
published by the Intermediate Technology Development Group,
London, England, describes how to recycle paper, plastics,
rubber, minerals, chemicals, oil, human and household
wastes, as well as metals. Mr. Vogler, an engineer, worked
Oxfam's "Wastesaver" program in developing
countries. He has done
much research in the field of recycling waste materials. The
Volunteer reviewer of this paper, David Reins, has been an
arts teacher for several years. He has also been a mechanic
and has worked with precision machines and sheet metal.
VITA is a private, nonprofit organization that supports
working on technical problems in developing countries. VITA
information and assistance aimed at helping individuals and
groups to select and implement technologies appropriate to
situations. VITA maintains an international Inquiry Service,
specialized documentation center, and a computerized roster
volunteer technical consultants; manages long-term field
and publishes a variety of technical manuals and papers.
UNDERSTANDING SCRAP METAL RECYCLING
VITA Volunteer Jon Vogler
A WIDESPREAD AND ANCIENT INDUSTRY
The recycling of metals is probably as old as other forms of
metal working, which the book of Genesis gives as the
of Tubal Cain, eight generations after Adam, who "made
of tools out of bronze and iron." Perhaps the earliest
is in Isaiah: "[they] shall beat their swords into
and their spears into pruning hooks." This is probably
the recycling of metals uses the same processes as the
of metal from ore. So important were these processes, that
civilizations were labeled by them. The "bronze
age" covers man's
first production of tools (other than primitive stone axes)
the 'iron age' of tools that would cut without losing their
Gold and silver money likewise has been repeatedly recycled:
melting down and casting or stamping new coins. Much of the
history of the modern world has been caused by the
of metals: the Spanish Conquest of Latin America in the
century was carried out because the gold and silver that
had been produced from ore by the Mayas and Incas could be
down and converted into jewelry and bullion for the King of
Little attention was paid to recycling during the industrial
revolution. Bessemer's invention of the blast furnace
1856) made it possible to produce new steel in huge volume:
only in times of war when the importation of metal ores has
prevented, has recycling flourished. The campaign to collect
aluminum saucepans to make Spitfire airplanes was enormously
popular in Britain in 1940. However, metal recycling is
politically significant: it was the presence of scrap-metal
collectors on a remote South Atlantic Island that triggered
war over the Falklands/Malvinas Islands.
Metal scrap, although unfamiliar to most people, is one of
world's larger industries with regard to the number of
and people employed, weight of material handled and value of
equipment used. It offers exceptionally good opportunities,
creating new businesses in developing countries, whose
or generation of scrap will increase rapidly with industrial
and urban growth. Governments like it because it saves foreign
exchange, conserves energy (recycling metals uses far less
than primary metal production from ores), and creates
THE METALS THAT ARE RECYCLED
It is convenient to split them into three categories: ferrous,
non-ferrous, and precious. Ferrous metals are those that
iron and the main difference is that these are cheap and are
recycled in huge quantities:
hundreds, thousands, or even tens
of thousands of metric tons.
Non-ferrous are those with no
iron: they include copper, aluminum, lead, and so on and
are much smaller: tens of tons or even a few kilograms
may be worth large sums of money. Precious metals include
silver, platinum, etc., and just a few grams may be very
Table 1. Typical
Scrap Metal Prices: Britain 1984
Price per Ton
New or detinned bales
Car battery plates
Because of these differences, the sources of scrap, the
into which they can be sold, and the methods, equipment, and
skills needed for recycling also differ greatly. In the main
of this paper the categories will be discussed separately,
the reader should note that there is much overlapping: for
certain furnace types may be used for all categories of
scrap and some types of scrap, such as tinplate which
steel (ferrous) and tin (non-ferrous), bridge two
the latter part of the paper, general principles of metals
will be discussed and these are applicable to all
Much metals recycling feeds recovered material (sometimes
secondary) back into the same industries that produced it in
first place (primary industries). To establish a business
will recycle metals profitably it is therefore essential to
familiar with the primary industries, especially with the
steel industry, so the sections on each metal will describe
II. IRON AND STEEL
The Production of Iron
Iron is a natural element, usually found as an
"oxide" of iron
mixed with other minerals and called iron ore. This is
a blast furnace to produce metallic iron called pig iron (so
called because the molds in which it used to be cast were
around a central channel like piglets suckling a sow!)
Pig iron has two uses. It can be melted in a foundry where
cast into molds to produce solid, heavy objects and objects
complicated shapes such as are listed below in the section,
Forge and the Foundry." It can also be made into steel.
The Production of Steel
Pig iron contains another material: carbon (familiar as coal
charcoal). Steel is iron with little carbon; steel making is
simply the removal of the carbon by burning. This makes the
steel stronger, more flexible, and easier to cut than iron.
There are many different processes for making; steel from
iron. All produce molten steel, which may then be cast to
an end-product. Steel castings are not as common as iron but
stronger. Steel may be cast into ingots for forging, the
of hammering hot steel, to make items of extreme toughness;
strength. It may also be cast into slabs blooms, or billets
rolling. (Slabs, blooms, and billets are chunks of steel
for further shaping.) Rolling is the most common process for
shaping steel. The billet is heated until it glows yellow,
passed forwards and backwards between powerful steel rollers
the correct size and shape to produce the cross-section that
required. Steel sections in turn may be cut, cold-rolled,
forged, welded, electroplated, or treated in many other ways
form the huge variety of steel components in use in the world
IRON AND STEEL SCRAP
Ferrous scrap can be fed back into the iron and steel
processes already described at any of a number of stages:
Scrap iron or steel may be melted in a cupola or rotary
furnace(see below for descriptions) to make iron or steel castings. It
is usually mixed with pig iron.
Steel Mill Scrap
Scrap steel, but not cast iron, may be melted in an
steel-making furnace and cast as billets for rolling.
Large pieces of scrap steel may be cut to regular shapes and
into new sections of a smaller size. Rerolling is practiced
widely in parts of Asia, but less elsewhere. Thick scrap
is flame cut into parallel-sided slabs that are heated in an
furnace (but not melted, so the furnace is simpler and
cheaper than that used in a steel mill and less energy is
It is then rolled in a four or five stand mill (a stand is
pair of rollers). Capital cost of the plant may be as little
US $180,000 (or even less for a used plant).
Rerolling is very suitable for thick plates from
(cutting up of old ships), an industry being adopted by many
Third World countries short of heavy scrap. It requires a
high degree of technical and manual skill and is not
as an activity to anyone without previous rolling mill
Steel may be used as a raw material and cut, formed, forged,
treated in any other way to fabricate new objects. Rerolling
re-use yield far more value from a given weight of scrap)
should be tried wherever possible. Two waste materials
special mention because they are so commonly used in this
oil drums and reinforcing steel.
Oil Drums. The
standard 45-gallon (200-liter) oil drum can be
used as a container for liquids or soilds; as a waste bin;
into a small (but short lived) furnace; mounted on a cart
or truck or cut open to make an animal feeding trough. It is
even more widely used as a source of raw material. When flattened
out, an oil drum makes a rectangular sheet of steel 180 x 90
plus two circular pieces 57 cm in diameter.
Concrete is often strengthened with steel reinforcing
bars. These are made in standard lengths and cut to
size on the construction site. The off-cuts are a useful
that can be cut with an ordinary hacksaw, bent across the
knee or heated in a simple charcoal forge to flatten or
In Kenya, a number of workers have developed a whole
using reinforcing bars and similar materials. These
men have made hand-operated punches, folders, and other
machinery, all from scrap metal. From these they manufacture
such products as heavy-duty bicycle carriers, stands
and foreguards (strengthener between forks and handlebars), small
agricultural tools, and metal working tools.
THE FORGE AND THE FOUNDRY
The forge and the foundry are two processes that can use
scrap to produce finished goods for re-sale.
provide excellent markets for the metal scrap reclaimer.
many Third World towns do not have a local foundry or forge
and the nearest is often many miles away. Not only is there
market for scrap metal, but all types of iron and steel
have to be brought in and are very expensive.
This situation may
justify setting up a small forge or foundry locally, which
create employment, provide a market for scrap metal (and
for scrap collectors and sorters); and provide cheaper iron
and steel goods with less delay and difficulty.
In order to flatten or shape a piece of solid steel it must
heated to red and then yellow heat, at which point it
softer and more workable. The furnace in which pieces of
may be heated is called a forge and the word is also used to
describe the complete workshop in which forging is done. For
working with reinforcing steel and similar sizes of scrap, a
forge may be very small with simple requirements, namely:
A bed of coal, coke, or charcoal
A source of draft (wind) through the bed
Tools for handling and hammering the hot
Products That Can be Made by Forging
such as hoes, rakes, mattocks,
axes, plow blades
for carts, trolleys, trailers
such as hammers, pincers, screwdrivers,
chisels, adzes, drill bits
such as stone chisels, trowels,
such as ramps, brackets, tow hooks
Fittings for boats
such as rowlocks and cleats
of all sorts, especially for the
many items described in this paper
such as baling presses, shears,
The Small Iron Foundry
Foundry work requires long training. The quality of locally
goods may be low, until skill and experience are obtained.
Mass produced goods, even those imported, may still turn
out cheaper despite the cost of transport. Foundry
needs organizing ability, practical skill, and
Equipment Needed for a Small Foundry
Storage space for scrap metal and means of
Furnace for melting the metal
Wooden patterns and a workshop for making
Molding and sand preparation equipment
Products That Can be Made In a Small Foundry
Table 2 is taken from a report on the foundry industry
by a developing country in the South American Andes and may
regarded as typical. No other process can produce
shapes so readily.
Table 2. Products
That Can Be Made In a Small Foundry
spare parts for machinery
manhole and drain covers
car and truck parts
weights and counterweights
shelving brackets bed
stoves and heaters
FURNACES FOR MELTING FERROUS SCRAP
Some of the major types of furnaces are described below and
in Table 3.
Electric Arc Furnace
The electric arc furnaces used in steel mills are huge,
of melting seven tons of metal per day upwards, and very
However, it is possible to construct a tiny model for
foundry work. It comprises a cylindrical pot, less than a
high, of alumina brick and magnesite. The brickwork is held
within a steel hoop mounted on a shaft that rotates in
simple vee-blocks. The lid, of fireclay encompassed by a steel band, is
penetrated by two graphite electrodes, which in turn are
copper clamps mounted on a tilting and lifting mechanism. A
of parallel- connected, direct-current arc welding
(such as those manufactured by Lincoln Electric Company)
current (of up to 1000 amps each at 40 volts) by thick
cooper cables to the electroded clamps. The generators are
off the three-phase main electric supply.
The furnace is charged with small pieces of scrap and the
lowered. The arc strikes from one electrode to the scrap and
back to the other electrode. As the charge melts, the
are lowered by hand wheels. It takes about one hour to melt
charge. The electrodes are used up in the course of
and have to be renewed, so the unit is not cheap to run
with other types of small furnaces. On the other hand, it is
flexible, handy to use for small batch work, and of
low capital cost.
A cupola is not unlike a small blast-furnace: a vertical
of steel plates, lined with bricks or other heat-resistant
to protect the steel from the intense heat generated. It has
a vertical, cyclindrical steel shell, with air holes above
The smallest practical size can produce just over one ton of
iron per hour from a charge of 140 kilos of iron and 20
coke in each layer. One kilo of lime or sea-shells is added
flux the iron (prevent oxidation and allow slag to drain
more easily through the slag hole at the back, which is
from time to time). It is cheap to build and operate but too
laborious to use for small quantitites of material. Once at
stretch it can melt about four and one-half tons of metal in
a working day. So, it is only operated about once a
Casting molds are stockpiled in preparation and the cupola
on heat until every mold has been filled.
Rotary Oil Fired Furnace
This consists of a steel cylinder with conical ends and the
of the cone cut off to leave a hole about half the diameter
the cylinder. The
cylinder is mounted inside circular turning
wheels that fun on slow, electrically driven rollers.
turning agitates the scrap and speeds melting.
Scrap and pig
iron are charged in through one circular end hole.
At the other
end is the burner, which uses gas or bunker oil blown
nozzle with air from a power fan.
Pouring takes place through a
spout in the middle of the cylinder wall.
Slag is removed
through a spout in one end. A separate cylinder is used for
different type of metal to prevent contamination.
The Crucible Furnace
The crucible furnace is used for small-scale operations,
often with non-ferrous metals but also for cast iron and
It differs from the furnaces just described in that the fuel
the metal are kept totally separate, giving much better
over purity and composition.
This is achieved by holding the
metal in a fire clay crucible that is seated inside the
the furnace can be coke-fired, oil or
gas are more convenient as they heat more quickly than coke,
more widely available, and are simpler to use in a tilting
The furnace and its lid are lined with firebrick and mounted
strong bearings at the center of gravity.
The oil burner flame
enters through a hole in the bottom while the burner pump is
behind the screen to prevent damage from slag or hot metal
work. The crucible
is suspended in the center so that it is
surrounded on all sides by a jacket of heated air. Tilting
hand wheel action through a reduction gear box. For higher
work, crucibles are made from graphite mixed with the
fire clay. They are
fragile when cold but strong when heated.
Each crucible should be used only for one type of metal.
This is similar to the crucible furnace except that the
is set permanently in the furnace, surrounded by a
electric coil. A high frequency (1000 cycles per second)
current is applied by a special generator.
creates a magnetic field that induces electric currents in
charge to generate heat and melt the scrap.
A large unit can
contain up to four tons of scrap and takes a little over an
to heat, but much smaller units are commonly used, even down
the laboratory models holding only a few pounds.
are expensive for their size.
Induction furnaces are very clean and there is no possiblity
chemical changes due to contact with fuel or the high
of the electric arc furnace, so they are very suitable for
non-ferrous metal and alloy steels.
Another advantage is that
cast iron can be made from steel scrap without the need for
The process is called recarburizing and requires
graphite charcoal and ferro-silicon additions.
A good combination for starting a small foundry would be a
for cheap, large volume casting, plus a small electric arc
induction furnace for small quantity work required quickly.
3. Furnaces for Melting Ferrous Scrap
or Solid pig
Oil Solid pig
coke cast iron
Pulverized Molten or
coal or oil
or large or high
THE SCRAP HANDLING PROCESS
Scrap is recovered from a variety of sources. Scrap handling
covers the processes of collection, grading, and
Sources of Steel Scrap
Off-cuts of reinforcing steel, rods and
mesh, wire and nails.
Poles, girders, joists, steel doors and windows,
drain covers, pipes, railings, grills, etc.
Off-cuts, swarf (turnings and chips from
lathes, drills, etc. , discarded motor parts, scrap cars.
Factories, mines, quarries, drilling sites, farms, technical
Discarded machinery, construction steel, partitioning,
drums and containers, pipes, tanks, carts, motors, in
Streets, parks, and waste land.
Discarded railings, manhole covers,
appliances (cookers, refrigerators, etc.),
tin cans, broken bicycles, perambulators (prams), toys,
Refuse dumps. Any of
This involves three main activities:
Negotiation. To buy
scrap, demolish machinery, clear scrap lying
in public places.
Handling. By laborer
or by crane, often with equipment for metal
cutting, unbolting, and loading onto vehicles.
Transport. By cart,
truck, railway, wagon, etc.
The use of skips can reduce costs significantly. A skip is a
steel container in which the supplier stores scrap for the
to collect with a specially adapted skip loader truck.
The equipment for collecting scrap metal includes the
a strong cart or vehicle is essential
boots with steel-reinforced toe-caps
block and tackle
Grading of Scrap
The following list of ferrous scrap grades should serve
selling scrap in a Third World country that has one or more
rolling mills, usually with electric arc furnaces, and a
of small or large iron foundries, plus workshops of
kinds. In countries
without such industry, different grading,
possibly aimed at export, will be needed. The grades
heavy melting scrap, also known as HMS or
medium scrap (or "No. 2")
light scrap (or "No. 2 bundles"
or "No. 3")
These may be in the form of:
re-rollable pieces (only if re-rolling
Cast Iron. Cast iron
can be identified by its dull grey color,
comparative weakness (it can often be broken by a hammer
and complicated cast shapes, sometimes with numbers or words
proud of (higher than) the surface.
It is one of the most valuable,
highly priced forms of scrap and can be sold to a local
Heavy Melting Scrap.
Whenever possible, steel scrap should be
sold directly to a steel mill. In Third World countries
mostly mini mills, using electric arc furnaces, which
follows: a first charge of scrap is melted, the glowing
withdrawn, the top cover swivelled away and a second load
of scrap discharged into the furnace from the charge basket.
molten metal that determines the economics of furnace
Valuable time and energy are saved by reducing the number of
times the furnace has to recharge.
For this reason, steelmakers
will pay far higher prices for smallish pieces of solid,
scrap more than 6mm thick which will form a heavy, dense
Scrap that fills this requirement is HMS and fetches an
price; bales of new or detinned sheet steel are even better
Obviously, large furnaces can accept much longer pieces than
mini mills. In
Britain, the maximum length of HMS is 1.5m.
Elsewhere, mini mill furnace diameters are often not more
and charge baskets 1.5m, in which case material of about
of a meter in length is preferable.
Medium Scrap. This
includes material which is thinner than 6mm
but is reasonably free from rust, dirt, and any metals that
difficulties in steel-making, especially tin and copper.
scrap may be sold to a foundry or steel mill.
The pieces should
be cut into lengths that will make a dense furnace charge
to obtain. It is not
economical to cut No. 2 scrap with expensive
gases; an alligator shear is essential.
Light Scrap (No. 2 bundles or No. 3).
This is the lowest acceptable
quality and fetches the lowest price.
It contains sheet
material that is not able to be included in No. 2 because:
it is too thin
it is too rusty
it is coated or contaminated with tin,
it is heavily coated with paint or oil.
Scrap Preparation Processes
Three mechanical processes are commonly used to prepare the
scrap-baling, shearing, and shredding.
Chemical processes are
also used in certain circumstances.
Baling. The material
is compressed in a powerful mechanical or
hydraulic press, to produce dense, cubical blocks called
Light scrap such as large, rusty sheets of galvanized (zinc
coated) steel are the worst forms of furnace feed, but even
can be made more acceptable (and that means a better price,
baling them. The advantages of baling are:
more weight can be loaded on a truck so
more material can be stored in a given
space so a
price can be negotiated for the larger quantity
the buyer finds storage is easier so will
pay a little
handling and loading are easier, quicker
a denser furnace charge is obtained.
material is chopped to length by a powerful blade.
The cheapest machine is an alligator shear that will cut HMS
20cm thickness. Larger shears are even more powerful.
Shredding. Used on
thin steel that may contain other materials
(glass, plastic, rubber, any non-ferrous metals, etc.) such
automobiles and household appliances. Hardened steel hammers
knives, driven by electric motors of enormous power, reduce
object to small pieces that can then be sorted, mainly by
that remove the steel scrap and leave all other material.
are usually very expensive to buy and run and are only
justified when huge numbers of objects are available to feed
through them. Most industrial countries have one shredding
for between two and five million people. Most
countries do not have enough motor vehicles or household
to justify the installation of shredding plants.
Used when metals are mixed (or mixed with nonmetals)
and not simply mechanically joined. Chemical methods are
often combined with electrolysis (the passing of an electric
current through a solution containing the metal
detinning of tin plate scrap
recovery of silver from photographic
wastes. This will
described under IV. PRECIOUS METALS below.
RECYCLING OF TIN CANS AND SCRAP FROM CAN MANUFACTURING
"Tin" cans are actually made of steel coated with
a very thin
layer of tin and often with lacquer as well.
They are a problem
to steel makers as the tin, which has a lower melting point,
causes zones of weakness in the hot steel, leading to hot
and other problems.
For this reason, cans are not used by
steel makers in the industralized countries unless the tin
been removed (or at least reduced) by detinning.
their use is restricted to the production of low-quality
such as reinforcing steel.
In many developing countries where there is a shortage of
scrap, used cans are accepted, provided they form less than
percent of the total scrap charge and are evenly dispersed
throughout: one steelmaker claims to use up to 50 percent
make reinforcing bars!
Some steel makers prefer cans rusted in
the weather for some weeks before use.
In the original manufacture tin is applied to the steel
either of two industrial processes.
The more modern is electrolytic
deposition, which results in an extremely thin layer of tin
(thickness 0.0015mm and weight 0.5 percent to 1.0 percent).
the older process, the steel was dipped in a bath of molten
resulting in a much thicker layer of tin: by weight 1.5
to 7.0 percent. Hot dipped tinplate scrap causes worse
Also, the amount of pure tin that can be
recovered from it is greater, which makes the removal
more profitable. Detinning is applied to scrap from can
but because they are dirty, which upsets the process,
only occasionally to used cans.
Detinning of Scrap Tinplate
This can be carried out in countries where tinplate cans and
boxes are locally manufactured in volume and where local
rolling mills or foundries export the steel scrap. Local
for tin are not essential as this metal can be sold
It finds virtually unlimited markets if the quality
is correct (this means composition of not less than 99.75 percent
tin). If it is
contaminated with lead (which often occurs in
can-manufacturing scrap) it may be sold for solder
only slightly lower prices.
Detinned steel scrap, if it is press-packed into rectangular
bales in a hydraulic press, fetches almost the highest price
is paid for steel scrap.
The tin content must be kept to below
0.05 percent but this is not difficult using the process
The major items of such a plant are a furnace constructed of
brick, with flues and grates firebrick-lined, containing
steel vats about one meter deep and in diameter, complete
chimney and forced draft fan.
Around the furnace is arranged a
low voltage electrical distribution system, to make the vat
into a cathode. The
anode is retractable so that it may be
lowered to make electrical contact with the scrap charge and
raised clear when the charge is positioned or withdrawn. A
to handle the full charge baskets is needed, as are pre-wash
post-rinse water tanks, a tin smelting furnace and refining
furnace with hand tools, and a scrap metal baling press. The
process requires a competent standard of technical and
Economics of Detinning
These will vary widely depending on local factors and, in particular:
steel scrap prices, local electricity tariffs, cheap fuel
availability, location and transport arrangements, and
tin metal can be sold locally. However, based on actual
for a 6,000 ton per annum plant in East Africa in 1981 it appears
At a scale of over 1000 tons per annum a
this kind can operate at a profit, given
costs and prices for developing countries that
own steel industry.
Profitability is substantially higher if
coating is greater, for example, where cans are
export of acid fruits.
Between 250 and 1000 tons per annum plants
if tin coatings are thicker than those used
Below 250 tons per annum, micro scale
plants make no
profit but can provide self-financing employment.
However, these principles are general; each country's
situation should be studied.
Table 4 presents a comparison of
the investment required and returns expected on various
small detinning plants.
Table 4. Investment and Profitability of Small Detinning
in thousands of U.S. dollars)
Plant Capacity in Tons per
Sales - Baled detinned steel
- Tin metal
(0.5 percent) 3
Total variable costs
Total fixed costs
Net profit before
Return on investment before tax
Number of workers
RECLAMATION OF MOTOR CARS AND SIMILAR VEHICLES
The junk motor car is an important source of steel scrap in
countries. It is fully discussed in Jobs from Junk (See
Car parts can be recovered by removal and sale of some
use of parts for scrap, and use of the shell for scrap.
Recovery of Saleable Components
Parts are worth much more when re-used rather than scrapped.
Every city in the world has dealers in second-hand car parts
in some towns a complete commercial district is devoted to
Recovery for Scrap
Unsaleable parts can often be used as raw material, e.g.,
springs can be cut and ground to make excellent chisels and
What is unusable goes for scrap: engines as cast iron or
radiators as copper, etc.
Recovery of Auto Shells
The shell is all that remains of the car when the parts have
removed. Shells abound in many parts of the Third World, not
only in cities and suburbs but also in rural areas.
They are a
hazard to traffic and to children and serve as breeding
mosquitoes and other pests.
However, their large size and low
weight of metal make them uneconomic to transport to a
steel mill or foundry.
Neither are there sufficient numbers to
justify investment in hugh car-crushers or shredders such as
those used in the industrialized countries.
Because people in some Third World countries are so
in car repair and obtaining used spare parts, cars often run
30 or 40 years, also diminishing the scrap supply.
Where large numbers of shells are accumulating, simple
methods may be used to reduce them to pieces small
enough for economic transport to the scrap buyers.
III. NON-FERROUS METALS
Metals other than iron and steel are described as
The most interesting as regards scrap are aluminum, copper,
brasses and bronzes, zinc, and lead.
One problem facing the collector is how to identify all these
different metals. They are used by quite different markets
the best prices are paid by the final users, normally
or refiners, who will not buy mixed or unidentified metals.
There are simple tests to identify a metal:
Find out where it came from
Consider the size, shape, and former use
of the item
Test it with a magnet; ferrous metals are
or to it;
non-ferrous metals are generally not
Look at the color
Drill or take filings.
Copper is the perfect material for recycling.
It is valuable,
easy to identify, easy to clean, and heavy. Moreover, it can
readily sold to small foundries or larger companies that
and produce copper sheet, wire, or bars. It has many
alloys, particularly bronze (which contains copper, tin, and
zinc) and brass (which contains copper-and zinc only).
from either is easy to sell.
Grading of Copper Scrap
Copper may be graded as follows:
Copper cables with plastic covering.
The plastic or
covering has to be removed and this can be done
in one of
three ways: by hand, by burning, or by using
stripper--a machine that chews off plastic,
copper wire unharmed.
Copper contaminated with tin
Copper contaminated with solder
Refining of Copper Scrap
This needs specialist skills.
The copper is furnace-melted and
molten sand added to form a slag.
Air is blown into the molten
mixture and iron, tin, and lead are all oxidized and float
sulphur, and other impurities are then given off
as gases. Some of the copper also becomes oxidized and has
reduced by poling: floating green tree trunks in the hot
copper (as in the smelting of copper ore).
Casting of Copper into Ingots
In a foundry, pure copper can be melted in any of the small
described above, and cast into ingots. It is worth investing
in cast iron molds. Special equipment to measure the furnace
temperature is necessary and specialist advice should be
Sources of Aluminum Scrap
Aluminum is one of the most widely used metals because it is
cheap to produce, lightweight, and very easy to work. The
tubes, boxes, containers for medicines and other
door and window frames
some drink cans
cooking foil, take-away food trays and milk
Markets for Aluminum Scrap
In developing countries the largest market will be small foundries,
but there may also be mills that melt the scrap to produce
ingots for conversion into sheets, extrusions, castings,
Most of these will buy aluminum scrap if its composition is
known, but may refuse to buy foil unless baled.
Foil may also be
sold to steelmakers, who use it as a deoxidant; it is ground
thrown into the crucible to reduce slag.
Grading of Aluminum
When collecting, keep known alloys separate from
pure aluminum. Thereafter, the main task is to remove all
materials such as plastics, oil, iron or steel, copper,
dirt, or the contents of containers.
The aluminum is then graded to:
dirty or "irony" heavy
foil and other thin material such as cans
Manufacture of Aluminum Ingots
The market for aluminum scrap can be improved by casting
A furnace is needed with a sloping hearth capable of
temperatures 200-300[degrees]C above that at which aluminum
aluminum will melt before any ferrous metals. and
will run down the furnace hearth into a trough, from which
be poured into open sand molds. The ferrous metals remain on
hearth, avoiding the need to remove them from the scrap
For suitable furnaces, see 'Equipment Suppliers' at the
end of this paper.
An Aluminum Foundry
Having successfully cast aluminum ingots, it may be possible
cast finished products.
This is not, however, an easy process
and some knowledge of foundry operations is vital.
Of the furnaces
described above, the rotary, induction, or crucible may be
used for aluminum.
It is possible to sand-cast aluminum in a manner similar to
iron, but, as aluminum is often used to make smaller
in far larger numbers, it may be economic to use
This replaces the sand mold with one of steel, accurately
and expertly designed, so that the metal will flow,
and shrink correctly.
Therefore, dies can be extremely
The simplest process is gravity die-casting: the metal is
into the heated die and the only pressure is from its own
A more complicated but faster process uses a pressure
that forces the molten metal into the die, ejects the
casting, and closes the die ready for the next cycle.
Zinc is a cheap, easily-cast metal used for castings where
strength is not important.
It is widely used for galvanizing
(protecting steel from rusting) and making brasses alloys of
copper and zinc).
Zinc casts easily and is widely used for die
castings but not all factories with die-casting machinery
zinc scrap. Metal of high purity is required and is alloyed
carefully controlled additions of aluminum (and sometimes
Zinc can easily be melted in a furnace at 400' to
500[degrees]C with a
chloride flux, but the metal obtained may not be pure.
pure metal can be obtained by evaporating the metal in a
atmosphere and collecting the vapor in a condenser (a steel
drum, cooled by water will do) from which it may be remelted
cast into ingots.
Products made from zinc include:
parts for cars (especially door handles,
small gear boxes, carburetors, etc.
washing machines and refrigerators
radios and televisions
printers' plates and type.
Lead, like copper, is an easy material to recycle if only
obtain enough of it.
Its grey color when oxidized, great density,
softness, and flexibility make it easy to identify.
same properties make it valuable. It is easy to store,
and work into its final shape.
Because it melts at a low
temperature (325[degrees]C) no special furnace is needed and
it is cast
by any industry that uses it.
Thus, the sources of lead scrap
are also the markets into which you can sell it, for
car battery plate solder
pipes for plumbing
flashings (waterproof joints) for roofs
gutters and spouts for rainwater
weights and counter-weights
wine bottle tops and seals
bearings of white metal (lead and tin)
lead covered cable.
Although lead is easy to melt, care is needed to ensure that
little lead scrap as possible is lost as fumes and dross
that floats on the molten metal).
This can be achieved by using
a flux and a reducing agent. The scrap is first washed in a
concentrated solution of sodium carbonate, to remove sulphur,
then smelted in a furnace at 800[degrees]-900[degrees]C,
using coke as the reducing
agent, and flux of soda ash, borax, and fluorspar.
Lead is a
poison and can cause fatal illness.
Any workshop handling molten lead should have fume
fans fitted and
employees should wear effective face masks,
wash before eating,
and have regular medical examinations.
IV. PRECIOUS METALS
Normally these are recycled by gold- and silversmiths. There
however, one important source of silver available to the
the recovery of silver from photographic materials.
The silver present in a wide range of photographic and X-ray
materials can be recovered as metal and sold.
The materials in
questions are of two kinds.
First, there are those used to
process photographs and x-rays, in particular, fixer
Silver is also contained in the actual photographs and
themselves, after they have been developed.
It can only be
recovered by destroying them when they are no longer
CHEMISTRY OF SILVER RECOVERY
In a photographic or x-ray film, silver bromide grains are
within a layer of gelatin known as emulsion.
gelatin is thinly spread on a sheet of transparent plastic
known as the support.
When the light from a camera lens falls on
the film, the silver bromide grains are sensitized in the
pattern as that of the light.
The places that receive the most
light have the most grains sensitized and, after developing,
contain the greatest amount of silver.
The silver is not in the
bright, shiny, metallic form with which we are familiar in
and cutlery, but has the appearance of a fine, black or dark
grey powder. Thus, the areas that were exposed to the most
become darkest and such film is called negative.
The grains of silver bromide that have not been converted to
silver are next removed by making them soluble in water, by
treating them with a fixer.
This is a solution containing a
chemical: most commonly sodium thiosulphate, often known as
After fixing, the negative is washed and all the soluble
thiosulphate removed, to leave only the metallic silver in
emulsion. To convert from the transparent negative to a
print, print paper coated with emulsion on a paper backing
exposed to light that has passed through the negative.
exposed paper is then developed, fixed, and washed in
It will be seen that a large proportion of the silver, which
begins life as silver bromide within the photographic
removed during the fixing process.
If only a little light fell
on the film, almost all the silver will end up in the fixer.
a large amount of light fell, most of the silver will remain
within the gelatin on the film.
There are, therefore, two
significant procedures for recovering silver from x-ray and
wastes: first, to extract it from the spent fixing
bath, and second, to recover it from the film, when this is
X-rays behave exactly like rays of light and identical
and support can be used for x-ray film, although it is
the support to be coated with emulsion on both sides,
photography, only one side is coated.
There is an important difference between color and
photography from the point of view of the recovery of
silver. Whereas in
black and white or x-rays a large percentage
of the metallic silver remains within the emulsion, in color
photography it is all removed, in a solution called
Color bleach-fix may therefore be very rich in silver but is
rarely available outside laboratories.
From Spent Fixer Bath
There are a number of ways in which metallic silver can be
small direct electric current is passed through
the fixer so that the silver is plated onto the cathode from
which it can later be removed.
Metal Ion Replacement.
The silver in the solution is replaced by
a more reactive metal such as zinc or iron.
Chemicals are added to the fixer, which precipitates
either silver or an insoluble silver salt, which is then
extracted by filtering, contrifuging, etc.
It is only necessary to release the silver from the
There are four principal ways in which this may be done:
By burning the support film and gelatin to
silver-containing ash, which can be reduced to silver
creates air pollution and much of the
lost as smoke.
Oxidizing the silver to a soluble oxide,
which can be
of the emulsion.
Dissolving the gelatin using an enzyme (a
of the proteolytic (which means protein
eating) type or an acid or alkali and then
silver from the residual sludge.
Reversal of the silver grains back to
dissolving in a fixer and electrolytic
SOURCES OF PHOTOGRAPHIC WASTES
advertising agents, newspapers, cinema,
photographic services, aerial photography,
engineering contractors, foundries,
clinics, dentists, hospitals
laboratories, micro-filming services
x-rays and film manufacturers and
V. GENERAL PRINCIPLES
WHAT IS NEEDED FOR METAL RECYCLING
The space can be unroofed but non-ferrous metals, which are
valuable, should be secure from theft. Because the process
ugly, screening by belts of trees or fences is common.
Prices for the sale
of recycled metals increase as the quantity
delivered increases. To achieve these improved prices it is
necessary to finance purchasing and collection (and often
preparation and further processing) before any sale is made.
Knowing the Customer. Dealers in scrap metal sell to a small
number of large and powerful customers and are often in
with many other scrap metal merchants. This weak bargaining
situation can be overcome only by knowing the customer and
business. The merchant should understand what each different
grade of scrap is used for and keep himself informed of
in the supply and demand of this product so that he can
shortages (and high prices) and surpluses (low prices).
Knowing the Collectors and Suppliers.
For supplies of material
the dealer is dependent on:
industrial producers of scrap who want
their premises clear, prompt payment,
gypsies and scavengers who want fair
prices and prompt
payment--or often advance loans or help with purchasing
Knowledge of Metals. The dealer must be able to distinguish
grades of metals at a glance or know what tests to apply.
Commercial Management Sense. Especially when handling
--ensuring enough cash to pay today's suppliers and labor
though the scrap may not be sold for days or weeks ahead.
Ability to Manage and Operate Plant. Small-scale scrap
can be done by hand but for the enterprise to grow,
essential: mechanical, electrical, and hydraulic systems to
under very rugged and difficult conditions. The successful
merchant must be able to obtain the services of qualified
obtain or stock necessary spare parts, operate regular
maintenance schedules, etc.
Awareness of International Markets. Knowledge of the grades
scrap in which the merchant deals and the economics of
to international markets when prices are depressed.
COSTS AND ECONOMICS
The main costs of collecting, dealing, and processing scrap
scrap from suppliers.
both to the sorting yard and from the yard to
the customer (or to the docks for export).
The economics of iron and steel scrap are
dominated by transportation costs as the
tonages and volumes are so large.
Energy Costs -
such as cutting gases, electrical power,
Labor Costs -
in industrialized (high wage) countries
significant unless reduced by heavy investment
in capital equipment. In developing
countries, both these costs will be lower.
Value Added -
profitability is higher if the dealer
a finished or partly finished product.
For example, a factory in Papua New Guinea
that recycled lead found it more
to cast fishing weights, which they sold
direct to marine stores.
Scrap Metal -
vary from one week to the next and from
Prices one country to another. Changes in
international markets may be found by
Materials Reclamation Weekly and
Metal Bulletin (See bibliography). Table 1
above gives current prices in Britain which
may be used for guidance only to show
values of different materials compare. It is
stressed that local prices may differ from
these by many hundred percent and anyone
dealing in scrap metals must
obtain local, up
to date commercial information.
CHOICE OF SCRAP PROCESSING TECHNOLOGY
Unsuitable technology can kill a promising scrap metal (or
other) business. Technology should be introduced in three
phases. Only when one phase has been fully mastered, free of
technical and maintenance problems for at least a year, and
a clear profit should the next phase be started. The phases
Establish suppliers, markets, and scrap grading operations,
manual labor and simple vehicles.
Merchandise scrap handling and sorting, using:
skip-loader vehicles and skips, or trucks
cranes with hydraulic or magnetic grabs
shearing and baling machines for scrap
Further processing of selected kinds of scrap in foundry,
etc., to add value to the product.
Before Phase 1 is started the decision must be made on what
of metal to recycle. The decision will affect the whole
for years to come and should be based on:
a survey of the markets for scrap metals
that can be
made from them
a survey of the available supplies
a calculation of the volume of metal that
a feasibility study (calculation of the
showing whether the business will have good
and profitability) in all three phases.
LAWS AND REGULATIONS
Dealers in scrap metal may be particularly affected by three
kinds of law:
Scrap metals are often so important to a country's economy
they may not be sold overseas. There may be restrictions on
imports of processing machinery and fuels.
Some scrap metal, especially copper, used for telephone and
electric power cables, is frequently stolen. Police after,
this by requiring scrap dealers to be licensed and to record
every purchase they make. The municipality or police may be
Safety of Employees
Handling scrap metal is dangerous! In many countries the,
requires the employer to safeguard his employees from all such
dangers by providing safe working methods, protective
medical checks, etc. Even if no laws apply, the victim of an
accident may have legal rights to sue the employer for
The dangers are very widespread and include:
injury from falling objects
injury and disease from poisonous
chemicals and gasses
explosion (of gasoline tanks, gas
burns and scalding, and
infection of wounds.
Alexander and Street. Metals in the Service of Man, Penguin
Bath Road, Harmondsworth, Middlesex, UB7 ODA,
Gross, John A. Metal Forging and Wrought Iron Work, Mills
Boon Ltd., 17-19
Foley Street, London Wla, 1DR, U.K.
Harper, John. Small Scale Foundries. Intermediate Technology
Ltd. 9 King
Street, London WC2E 8HW, U.K.
Intermediate Technology Development Group. The Iron
Profile, Intermediate Technology Publications
Ltd., 9 King
Street, London WC2E 8HW, U.K.
Intermediate Technology Development Group. Jobs from Junks:
Employment and Tidy Up Delerict Cars. Intermediate
Publications Ltd., 9 King Street, London WC2E
Intermediate Technology Development Group. Oil Drum Forges.
Publications Ltd., 9 King Street,
London WC2E 8HW,
Materials Reclamation Directory, P.O. Box 109, Maclaren
Croydon CR9 1QH, U.K.
Materials Reclamation Weekly, P.O. Box 109, Maclaren House,
CR9 1QH, U.K.
Metal Bulletin, 45, Lower Marsh Street, London SE1, U.K.
National Association of Recycling Industries. Recycled
Eighties, National Association of Recycling Industries
Avenue, New York, New York 10017 USA.
Small Industry Research Institute. Several reports, Small
Institute. P.O. Box 2106, 4/43 Roop Nagar,
Stimpson and Gray. Foundry Work, American Technical Society,
United Nations Industrial Development Organisation.
Demonstration Foundry in a Developing
UNIDO, Felderhaus, P.O. Box 707,
Pioneer Equipment Co., Ltd.
Old Padra Road,
Gas Cutting Torches
British Oxygen Co., Ltd.
W. Pimbo, Skelmersdale, U.K.
Metal Scrap Machinery
J. McIntyre (Machinery) Ltd.
Acorn Park Industrial Estate
Harrimans Lane, Dunkirk
165 Garth Road
Morden Surrey, SM4 4LH U.K.
Hydraulic and Engineering Works
10066, First Floor
D.B. Gupta Road
Pahar Ganj, New Delhi 110055, India
Hindustan Brown Boveri Baroda Ltd.
264 Dr Annie Besant Road
Bombay 43005 India
G.E.C. of India, Ltd.
Mukand Iron and Steel works
Davey Ashmore India Ltd.
A.C.C. Vickers-Babcock Durgapur, Ltd.
18th Shahabad Floor
Bombay 430021, India
G.L. Murphy Ltd.
Menston LS29 6AA
W. Yorkshire, U.K.
Metpro Machinery Ltd.
North Road Industrial Estate
Bridgend, Mid Glamorgan U.K.
Units 4 & 5
New Road, Newhaven
East Sussex, U.K.
The X-Rite Company
4101 Rogers B. Chaffee Drive
S.E. Grand Rapids, Michigan 39508 USA
Photographic Silver Recovery Ltd.
Royston Herts SG8 6DN, U.K.
Vogler, Jon. Detinning. INTERWASTE, 40 The Avenue, Roundhay,
Leeds, LS8 1JG, U. K.
Weygers, Alexander, G. Forging by Hand, Van Nostrand
Co., 450 West 33rd Street, New York, New York 10001 USA.
Weygers, Alexander G. Recycling, Use and Repari of Tools,
Nostrand Reinhold Company. 450 West 33rd Street, New York,
New York 10001 USA.
1. British Secondary
Metals Associations, 40 Oxford Street,
London Wl, United Kingdom. Telephone 01-580-5228.
2. British Scrap
Federation, 16 High Street, Brampton, Huntingdon,
Cambs PE18 BTU, United Kingdom. Telephone: 0480-55249.
International de la Recuperation, Place du Samedi,
13-BTE 4, 1000 Brussels, Belgium. Telephone (02) 217-82-51.
4. Interwaste, 40
The Avenue, Roundhay, Leeds LS8 1JG, United
Kingdom Telephone: 0532-661885.
5. The Institute of
Scrap Iron and Steel, Inc. 1627 "K" Street
N.W., Washington, D.C. 20036 USA
Association of Recycling Industries, 330 Madison
Avenue, New York, New York 10017 USA