Encyclopedia of Environmental Science and Engineering, Volume I and II

MANAGEMENT OF SOLID WASTE 663

FIGURE 7 Monsanto-Landgard waste pyrolysis process. Credit: Monsanto Enviro-Chem Systems Inc.

RECEIVING

SHREDDING

STORAGE

SOLIDS

WATER

QUENCHING

MAGNET

KILN

GASES

GAS PURIFIER

GAS SCRUBBER

CLEAN AIR TO

ATMOSPHERE

STACK

AIR HEATER

WATER CLARIFIER

FAN

RESIDUE

except in the case of palpable threat to human health and/or

the environment, avoidance of these types of items is largely

a mater of consumer choice. Nevertheless, some local gov-

ernments have begun restricting the use of certain types of

plastic, nondegradable or other materials.

Beverage container deposit legislation, mentioned above,

is a good example of an issue which straddles the areas of

source reduction and recycling. If a mandate to use only

refillable containers is utilized, certainly waste generation

will be decreased. This is clearly source reduction. However,

the mandate that deposits be utilized to encourage the return

of used containers is a recycling initiative, since the returned

bottles and cans will be used as secondary materials rather

than being refilled on a unit basis.

Disposable products may also be manufactured using

less raw materials as another alternative to achieve measur-

able source reduction gains. Obviously the limiting factor

here is the production of a product which contains less raw

material but still serves its intended use.

Extending the useful life of non-disposable products is

another legitimate source reduction alternative. The use of

alkaline rather than lead acid batteries is a good example.

The use of rechargeable batteries rather than disposable bat-

teries is an even better example. As another example, con-

sider the use of automobile tires which have a longer useful

life. Tires are currently produced (and disposed) at a rate of

220 million unit per year. Any tangible extension of useful

life for individual tires would decrease this generation rate

and avoid any increase in the current estimated 2 to 3 billion

discarded tires currently stockpiled.

The reduction in the toxicity of wastes is another impor-

tant source reduction measure. Among the materials of

greatest concern are lead and cadmium. The presence of

these and other heavy metals in incinerator ash often results

in the classification of such ash as a hazardous waste. Hence

the desire to identify the likely sources of lead and cadmium

and ultimately, to find ways to eliminate or replace these ele-

ments in the products which contain them.

The most current data available indicate a total of 213,652

tons of lead and 1,788 tons of cadmium in the municipal

solid waste generated in 1986. The figure for lead does not

include the lead present in the lead acid batteries which were

recycled which amounts to some 80% of the batteries pro-

duced. The primary sources of lead entering municipal waste

TABLE 25^39

Langard pyrolysis system typical stack gas analysis

Component Average value

N 2 40%

O 2 3%

CO 2 7%

H 2 O vapor 50%

Combustibles None

NO 4 50 ppm (vol.)

SO 2 100 ppm (vol.)

Chlorides 10 ppm (vol.)

Particulates 0.06 grains per SCF dry gas corrected to 12% CO 2

TABLE 24^38

Reduction of garbage by hydro-oxynation 52 1 BBL of oil ton of

garbage (50% cellulose)

Conditions

1500 psig initial pressure. 5000 psig operation pressure

350°C.

Addition of CO + H 2 O

Yield, wt%

Oil 40%

Residue 10%

H 2 O 27–36%

CO 15–20%

Other 2%

Oil Analysis C 83%, H 2 7.8%, O 2 7.8%, m N 2 1.9%, S 0.13%

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