MANAGEMENT OF SOLID WASTE 659
In certain areas such as paper, with 11 million tons recy-
cled in 1968 (25% of consumption), aluminum with 700,000
tons recycled (30% of production), copper with 1.5 million
tons recovered, and iron and steel salvage are an important
source of raw materials. Unit salvage values are summa-
rized in Table 22. Automobiles are regularly recovered; it is
economically a break-even operation once the auto body is
delivered to the salvage operation.
Mixed waste such as municipal refuse has not been a
major source of this salvage and contains large amounts of
additional metals as well as other potentially valuable mate-
rials. However it is only recently that essentially total recov-
ery has been considered. That is, “waste” is being looked at
as a potential “natural resource.” As an example, one com-
pany, Industrial Services of America, operated a separations
plant for industrial solid wastes where odor is no problem
and manual separation is feasible in the late ’40s.
One of the major problems of recycle and reuse has
been separation. Most ferrous metal is easily separated by
magnetic means, but other waste separation requires hand
picking, which is very costly. This method can also createpublic nuisance in that the odors from such operations can
be significant and have resulted in the closure of several such
operations. Studies in the late ’60s by the Bureau of Mines,
Stanford Research Institute and others provide potential
alternates for waste separation, but these have not found
wide commercial application.
The work at SRI is particularly interesting because it is
intended as a total separation process; waste is shredded and
then classified into components by density in an air classi-
fier.^32 While the process has not achieved separation of mate-
rials with densities that are close together (and much refuse
is in the situation) the concept as illustrated in Figure 4 is in
the right direction and should lead to promising results.
Similar work has been piloted using a hydrapulper to sep-
arate organic, glass and cellulose from metal. Hydrapulping
as developed by Black Clawson Company costs about $6 per
ton of feed.^33 A demonstration unit (Figure 6) with a 70 T/day
capacity was operating in Franklin, Ohio, using the Hydraposal
system (of which Hydrapulping is a part). Installed costs were
about $14,000/ daily ton for a 300 T/day plant with net operat-
ing cost of about $4.5/ton. About 400 pounds/ton of Fiber are
reclaimed along with glass cullet, metals and steam. A mate-
rial balance is shown in Figure 5. However a dry separation
such as that proposed by SRI may have significant advantages
over wet separation because the removal of water from cellu-
lose is a very costly operation. The fiber from Black Clawson
was fed to a roofing paper mill.
The aluminum industry, for example, as shown in
Figure 6, has suggested a process for taking municipal refuse
and separating it into aluminum, other nonferrous metals, fer-
rous metals, glass and other waste. Dr. James Etzel of Purdue
piloted a process, based on hydrapulping, which handles
sewage and solid waste and yields metals and a slurry con-
taining fine particles of glass and organics which can be fur-
ther treated or used as a soil supplement. Such techniques
require considerable additional development and refining but
will be one of the key waste management tools of the future.
Pyrolysis, once thought to be a promising process, has
not yet found wide acceptance. However, it remains techni-
cally feasible. Pyrolysis is the thermochemical degradation
of complex organic molecules into low molecular weightTABLE 21
Waste processing investment and operating costs (1980 basis)Method Investment $/ton daily capacity Operating costsa $/tonSanitary landfill 5–20 10–40
Hazardous landfill 10–40 30–100
Central incineration
No waste heat recovery
Waste heat recovery40,000
10,000–80,00030–50
40–80b
Composting 12,000 8–12ca Per ton of capacity, based on 2–20 foot lifts.
b No allowance for value of steam, which will be between $1.00 and $2.00 per ton.
c 3 shift operation 450 tons/day.TABLE 22
Value of reclaimed waste, average 1980 prices$/tonPaper
Newsprint 3–25
Other sorted Up to 50a
Glass 3–90
Cotton 4–20
Metals
Iron and steel 10–60
Copper and brass 270–800
Aluminum 160–250
Lead 70–160a Depends on type, color, etc.C013_002_r03.indd 659C013_002_r03.indd 659 11/18/2005 2:27:21 PM11/18/2005 2:27:21 PM