Hydrogen chloride and sulfur dioxide can be krubbed from the flue gases with water and chemal solutions, but this may produce water-pollution problems unless proper provisions are made for the treatment and disposal of the waste waters. In additen the cooling of the flue gases interferes with efective atmospheric dispersion. No satisfactory process is available for the removal of nitrogen oxides from the hot, dilute incinerator stack gases, and atmospheric dilution and dispersal are the only means now available to prevent the buildup of excessive concentrations in the vicinity of the ground. Because higher flame temperatures favor the fixation of larger amounts of nitrogen, high-temperature modem incinerators form more of these compounds. In most communities emissions of these inorganic tases from municipal incinerators are not regarded as a senous problem when they constitute the sole air contaminants from these operations and when they are emitted at high temperature from tall

stacks

There has been considerable interest in the United States in 2 European practices: extracting useful heat from the burning of refuse; and composting of solid wastes.

Heat recovery The heat content of typical American municipal refuse collections is about 5000 British thermal units (B.T.U) per pound. When it is realized that coals of various grades contain 12,000 to 14000 BTU per pound, it is apparent that, in the aggregate, municipal refuse, composed largely of paper products, is a substantial fuel resource. In Europe coal and oil have been relatively expensive as compared to their cost in the United States, and this has made recovery of the fuel value in refuse more attractive to the European countries. Also, the extra manpower required to burn trash has been less of a burden in the lower-wage European econemy In addition, most of the European powergenerding stations that make steam from refuse are mipally owned, and this seems to make the construction of combined conventional fuel and ree-burning central stations more attractive than

the United States, where it is more usual for power-generating stations to be operated by private stay companies or by regional governmental authorities that have no responsibility for refuse collection and disposal. There are exceptions, however. The Boston Municipal Incinerator, completed a few years ago, produces steam for the adjacent Boston City Hospital Although the incinerator must burn nabstantial quantities of supplementary fuel to meet the hospital's total requirements (in part, because the heat-release rate of the refuse has not been as great as was estimated originally) some of the heat

e in the refuse is being recovered. Many United States incinerators utilize heat in the flue gases to provide space heating and hot water for the incinerator plant, and a new incinerator on Long Island, New York is equipped to use waste heat to desalinate sea water by distillation. It is likely that the

utilization of heat produced in incinerators for municipal purposes will continue but there appears to be little interest on the part of United States utility companies in utilizing this form of fuel. There are many technical reasons why this attitude is unlikely to change in the foreseeable future.

Composting. The practice of solid waste composting is well developed in certain European countries, especially in Holland, Germany and Switzerland. The microbiologic degradation of organic substances before return to the soil is a well established agricultural process, and when animal manure is composted with plant refuse, the product has fertilizer value and contains valuable soil conditioners. Municipal refuse collections in the United States, composed largely of paper and lacking the rapidly degradable organic component lost to the garbage grinder, contain little compostable matter. Consequently, compost made from United States refuse collections contains virtually no fertilizer value, and its only uses are for ground cover and soil conditioner for heavy soils. It has about the same properties as peat moss. American farmers have shown no interest in this product, for it is difficult to apply to fields by automatic machinery and the cost of spreading or working it into the soil exceeds the benefits that may be obtained. Although several experimental composting plants have operated for brief periods in the United States, they have been uniformly unsuccessful in disposing of their product to farmers. It has been proposed that processors use the fiber for a carrier and diluent of highly concentrated chemical fertilizers, but it does not seem that that the market for this product (to be used on lawns and gardens) will support more than a few composting plants. Large-scale utilization of composted waste would require acceptance by large-scale farmers, who are generally to be found quite remote from the urban centers where the waste originates. Perhaps it could be managed if each householder were willing to accept a bag of composted waste in exchange for his weekly refuse accumulation.

European farmers are also not very enthusiastic about compost from municipal refuse, but some have been persuaded to accept it when the price is not much in excess of the cost of transporting it from the composting plant and the fertilizer value of the product has been raised by the addition of sewage sludge to the raw refuse. The heat generated by the microbiologic activity of composting is sufficient to destroy disease-producing bacteria in the sludge after a few days, and the mixture is safe to put back on the soil after a few months of aging. Many Europeans see composting of municipal refuse primarily as a means of disposing of sewage sludge, presently a grave problem in central Europe. Many advocates of composting in the United States, including manufacturers of composting machinery, have tended to stress financial gains from selling the end product. This is probably a mistake because the income

3-57 ()-69 pt. 1 - 4

from selling composted refuse is always likely
to be far short of covering the costs of manufacture.
However, this approach to composting is probably
unfair, for other refuse-disposal methods are not
required to pay their own way. It should be enough if
the net cost of composting, including sales, is no
greater than the cost of other acceptable methods.
Although all previous composting plants in the
United States have proved unsuccessful for tech-
nical and financial reasons, the new Office of Sol-
id Wastes is preparing to support operational dem-
onstrations of the leading composting processes over
a period of several years to resolve, once and for all,
whether this is a reasonable refuse-disposal method
in the United States.

NEW REFUSE-Disposal MethODS

Other projects currently supported by the Office
of Solid Wastes include research on incinerator
ships at Harvard School of Public Health. Under
this plan waste collections would be transported to
dockside and transferred to an ocean-going vessel.
When loaded, the vessel would put to sea, burn the
wastes and discharge the residue into deep holes in
the ocean floor. Studies are under way to determine
the biologic effects of incinerator residue on marine
species ranging from phytoplankton and lobster
larvas to flounders and clams. Acute and chronic
toxicity tests over a period of a year have shown no
detrimental effects from well incinerated residue at
concentrations up to two or three times those likely
to be produced locally during full-scale ship opera-
tions. Meteorologic measurements and analyses are
under way over offshore waters to locate ideal burn-
ing sites that will avoid the movement of stack dis-
charges to the shore under all weather conditions.
Systems analysis and high-speed computational ma-
chines are being employed to devise economical
methods of moving wastes to the water front, and
engineering studies are being conducted to develop
incineration and material-handling equipment espe-
cially adapted for ship use. Preliminary cost analy-
ses indicate that this method of waste handling
compares favorably with land-based incineration.
Convenient dumping grounds (that is, holes in the
ocean floor) located offshore of coastal cities, and
already approved by the United States Coast Guard
and Army Engineers and shown on current marine
charts, are adequate for handling the residue from
ship incinerators for a hundred or more years. It ap-
pears practical, therefore, to utilize the vast assimi-
lative capacity of ocean waters and the ocean at-
mosphere to solve a troublesome urban problem.
Studies show that this can be done without pollut-
ing the environment, decreasing the recreational use
of the waters or interfering with commercial and
sport fishing. Other disposal methods presently in
the development stage that utilize the ocean include
compression packaging of wastes and disposal of the
sealed packages in ocean deeps.

Many new incineration processes are also under

development. One, utilizing an iron-melting cupola,
or blast furnace, reduces the residue from all man-
ner of wastes to a glass-like slag that may be broken
up and used for clean fill in road building or as an
aggregate for cement. The ability to handle wastes
that are ordinarily classed as incombustible and the
compactness of the residue are noteworthy, but the
need to purchase supplementary fuel (coke) to melt
iron, clay, sand and similar refractory materials may
lead to excessive costs. In addition, severe flue-gas
cleaning problems are created by the blast of hot air
that rises when the falling refuse is fed into the top
of the furnace. Methods for cleaning the stack dis-
charges to a satisfactory sanitary standard are avail-
able commercially, but the cost will be high.

SOLID-WASTE COLLECTION

Although disposal creates most of the solid-waste
problems collection and transportation of refuse to a
disposal site represents up to 80 per cent of the
total system cost. It has been noted that "it costs
more to dispose of the New York Sunday Times
than it does a subscriber to buy it." Therefore, if
substantial economies of operation are to be
achieved, they must be looked for in this sector.
The widespread use of large packer-type trucks has
greatly increased the quantity of refuse that can be
collected between trips to the disposal facility. The
use of garbage grinders by entire communities
makes it possible to reduce pickups from twice to
once a week, or even once in two weeks, thereby
effecting substantial savings in collection costs. This
practice increases processing costs at sewage-treat-
ment plants, but the net savings will be substantial

Plans for the future include development of mo-
bile incinerators that can travel the streets and com-
bine the collection and disposal function into one
operation. Conveniently located city gas may be
used to assure complete combustion of the refuse.
even during wet weather; water is available to
scrub the particles and soluble gases from the flue
gases, and the residues can be dumped into the
city's sewage system for disposal at the treatment
plant. Also under consideration are powerful grinders
and modified water-carriage systems that will be
capable of reducing refuse as well as garbage to a
pulp suitable for transport to a central treatment
facility. Ultimately, it may be possible to eliminate
completely the use of glass bottles and metal cans
so that all but a few large objects may be handled
in household grinders. Development of these and
other new methods of waste collection are being
stimulated and assisted by the Office of Solid Wastes.

Junk automobiles present a special problem of
solid-waste disposal for municipalities. New York
City alone picks up from the streets about 25,000
abandoned cars per year, and other large metropol-
itan areas have similar experiences. Approximately
6,000,000 cars were scrapped in 1965. Some of
these were salvaged, and some joined the 25.000,-
000 to 40,000,000 already stored in dumps. Each

automobile in the United States contains about 11⁄2
tons of metals, principally iron and steel. The cop-
per radiator, lead battery, cast-iron motor block and
some other special parts are easily removed and
fnd a ready market. The steel body shell has little
value to steel makers, however, until it is separated
from glass, upholstery, rubber and other nonferrous
materials that make up the usual automobile body.
For many years, it was customary in junk yards to
drain the gasoline from the junked car, pour it in-
ude the body and ignite it. The resulting fire con-
sumed the upholstery, shattered the windows and
otherwise removed sufficient nonferrous materials to
make the product clean enough to be acceptable to
steel manufacturers. These fires produced enormous
clouds of black, sooty smoke and were severe local
ar-pollution nuisances. Consequently, open burning
of automobiles is prohibited in most urban areas,
and specially designed incinerators, continuous and
batch type, with gas-fired afterburners and tall
stacks were developed for this purpose. These
proved to be satisfactory from the air-pollution-con-
tro standpoint but were costly to operate because of
fue requirements and low production rate. The
increase in processing cost caused by more stringent
ar-pollution control regulations, combined with a
reduction in demand (and price) for steel scrap be-
cause of technologic changes in steel-making meth-
ods resulted in the buildup of large inventories in
junk car yards

A newer way of handling stripped automobile
body shells called the Proler process) is to place
them in giant hammer mills and reduce them to
small pieces of steel, cloth, rubber and so forth that
can be separated magnetically. The product is clean
steel scrap in the form of fist-sized fragments that
are easily handled for loading and unloading, pack
weli for economical shipment and melt easily in the
stees fumace. The nonsteel residue is buried. A
single full-scale plant of this kind can handle 1000
body shells per day One, soon to be operational in
the Boston area, will be capable of handling all the
punked cars in New England, and there appears to
be a profitable market for all the steel scrap that can
be produced by this process.

NONURBAN SOLID-WASTE PROBLEMS
Worsome solid waste problems also exist outside
metropolitan areas These include mining refuse of

all kinds and the severe disturbances to ground and
water caused by large-scale strip mining. Agricul-
tural waste-disposal problems are countrywide,
ranging from long standing and severe pollution of
Long Island's inland bays by duck-raising farms and
duck-packing plants to enormous accumulations of
manure in California's cattle-raising western valleys.
However, these special problems are outside the
scope of urban solid-waste management.

CONCLUSIONS

An urgent need for better methods of solid-waste
management in all sectors of the economy, com-
bined with the powerful stimulus provided by Solid
Waste Act funds, is opening up a period of active
development and experimentation in solid-waste
technology that will result in the rapid introduction
of the modern systems now needed. The need will
be even more urgent by the end of the century. A
most hopeful sign is the current interest among
universities and research institutions in tackling
solid-waste problems as an interdisciplinary study
involving the special skills of urban planners, so-
ciologists and economists, with those of sanitary
engineers, public-health administrators and public-
works specialists.

1

REFERENCES

American Public Works Association. Committee on Solid Wastes
Refuse Collection Practice. Third edition Chicago. Public Admin-
istration Service, 1966. P 27

2. Wegman. I. S. Cated in Refuse Collection Practice.

3. Gilbertson, W. E Solid wastes: worsening urban problem.
Presented on September 12, 1966, before Public Works Congress
sponsored by American Public Works Association, Chicago, Illinois.
4. First, M. W., Viles, F. J., Jr., and Levin, S. Control of toxic and ex-
plosive hazards in buildings erected on landfills. Pub. Health Rep
81:419, 1966.

5. President's Science Advisory Committee. Environmental Polution
Panel. Restoring the Quality of Our Environment. The White House,
November, 1965. P. 17

6. Committee on Science and Astronautics, Subcommittee on
Science. Research, and Development, United States House of Re-
presentatives, 89th Congress, 2nd Session. Everonmental Pollution A
challenge to science and technology Washington, DC - Government
Printing Office. 1966. P. 44

7. National Academy of Sciences-National Research Council,
Committee on Pollution. Waste Management and Control A report to the
Federal Council for Science and Technology Washington, D C Na-
Donal Research Council. 1966. (Pub. No 1400.) P. 32.

8 American Public Works Association. Municipal Refuse Disposal
Second edition. Chicago Public Administration Service. 1966 P 92.
9 Bowerman, R. F, and Dair, F. R. Supplemental refuse transpor
tation for incineration. Presented at 1966 National Incinerator Con-
terence, American Society of Mechanical Engineers, New York City,
New York, May 2, 1966.

10. Time 88 (21) 57, November 18, 1966.