EPA/530/SW-75d.
Baltimore Demonstrates Gas Pyrolysis

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BALTIMORE DEMONSTRATES GAS PYROLYSIS
THE ENERGY RECOVERY SOLID WASTE FACILITY IN
BALTIMORE, MARYLAND
The first Interim report (sw-75d.i) on work performed
under Federal solid waste management demonstration
grant No. S-801533 to the City of Baltimore was
written by David B. Sussman.
U.S. ENVIRONMENTAL PROTECTION AGENCY
1974

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This report has been reviewed by the U.S. Environmental Protection Agency.
Its publication does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of commercial products constitute endorsement or recommendation
for use by the U.S. Government.
An environmental protection publication (SW-75d.i) in the solid waste
management series.

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FOREWORD
Growing concern for the environment has changed our thinking about
solid waste. Although disguised as a nuisance, solid waste can be an
environmental asset. It contains a wealth of recyclable materials—
paper, cardboard, metals, and glass and offers the potential for con-
serving a seriously diminishing resource—fossil fuels.
In this period of concern about shortages of energy and material
resources, the mere existence of untapped resources commands our
attention. Recycling and reuse of waste materials makes good sense
environmentally and economically. Information is emerging to show
that recovering and reusing our resources is sound practice for more
reasons than those that are obvious. For example, when two production
systems are compared, one using virgin materials, the other secondary
or waste materials, the system using wastes almost always causes less
air and water pollution, generates less solid wastes, and consumes less
energy. This is true if the environmental impacts of all activities
in a system are measured—mining, processing, fabrication, manufacturing,•
and the transportation and disposal steps in between.
The Nation's task, then, is to organize our systems and institu-
tions so that the economy can begin to receive the benefits and reflect
the savings from using more secondary materials. One way to help
accomplish this is through new technology. But technological advances
are usually expensive, are relatively untried, and therefore entail
some risk. The Resource Recovery Act of 1970 enabled the Federal solid
waste management program to assist States and municipalities by assum-
ing part of the risk of trying new technologies. The result was a
significant expansion of the Federal resource recovery demonstration
program. This report describes one part of that program: the recovery
of energy in the form of steam by converting solid waste into a com-
bustible gas through a pyrolytic process, and then using the gas as a
fuel to fire a steam boiler.
The pilot process was developed by Monsanto Enviro-Chem Systems,
Inc., St. Louis, Missouri. In July 1972, the City of Baltimore applied
for a grant to demonstrate the Monsanto "Landgard" system with a full
scale pyrolysis plant. The concept presented by the City looked
encouraging. Consequently, the U. S. Environmental Protection Agency's
office of Solid Waste Management Programs awarded a grant to the City
of Baltimore for 40 percent of the cost of the project.
Construction began in early 1973 and full-scale operation is
scheduled in early 1975.

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ii
This demonstration exemplifies the kind of creative solutions that
government at all levels, industry, and the public must pursue to bring
our environmental and resource conservation problems under control.
Arsen J. Darnay
Deputy Assistant Administrator
for Solid Waste Management Programs

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BALTIMORE DEMONSTRATES GAS PYROLYSIS
THE ENERGY
RECOVERY SOLID WASTE FACILITY
IN BALTIMORE, MARYLAND
Converting municipal solid waste into energy is a solid waste
management option that has recently become attractive, both environ-
mentally and economically. Although a number of European countries
have been generating steam and electricity from municipal solid waste
for years, recovery of energy from municipal solid waste has been
limited in the United States. Until recently, it consisted of relatively
inefficient waste-heat boilers installed in conventional incinerators.
In the past five years, however, more sophisticated solid waste incinera-
tors have been built, which incorporate boilers for the recovery of
steam.
But these newer facilities, known as waterwall incinerators, have
several important limitations. First, the ability of these incinerators
to meet and maintain clean air standards economically is questionable.
Pollution control of incinerators is expensive and technically difficult.
Secondly, new facilities are relatively expensive both in capital and
operating cost. Third, their relative reliability has not always been
acceptable. Fourth, the energy conversion efficiency is somewhat less
than desirable.
By converting solid waste into a new fuel and burning the fuel in
a boiler, the above limitations can be reduced. While the pyrolytic
conversion of solid waste into steam is not a panacea for either the
solid waste problem or the energy crunch, it certainly can be a
significant part of the solution to both. The concept was considered
attractive enough for the City of Baltimore to undertake this innova-
tive venture with financial support from the U. S. Environmental
Protection Agency's Office of Solid Waste Management Programs. The
project is scheduled to be processing waste in early 1975.
INTRODUCTION
Project Objectives
The primary objective of the project is to demonstrate the technical
and economical feasibility of recovering energy from mixed municipal
waste using a gaseous pyrolysis process. Pyrolysis is the physical
and chemical decomposition of organic matter brought about by the action
of heat in an oxygen-deficient atmosphere. In order to meet the
objective, the City of Baltimore is building a full size 1,000 ton per

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2
day plant that will receive mixed municipal solid waste, including white
goods*, tires, and eventually sewage sludge**. The plant will generate
steam, recover ferrous metals, and produce char and a glassy aggregate
product. The project includes the design, construction, operation and
evaluation of a system that will convert most of the input waste into
useable products. It will receive approximately one half of Baltimore's
residential solid waste.
The project also will evaluate the marketing of steam, ferrous
metals and pyrolysis residues.
Benefits
The project has many potential benefits. The most important ones
are: (1) the disposal of about one half of the residential solid waste
of the City, without environmental degradation, (2) the energy recovered
from the waste in the form of steam and the associated saving of fossil
fuels, and (3) a disposal cost that is, based on preliminary economic
analysis, less than landfilling and incineration.
Project Participants and Their Roles
EPA awarded $6 million toward the cost of the $16 million project.
The Federal share was provided under the authority of Section 208 of
the Solid Waste Disposal Act, as amended.
The Maryland Environmental Service (MES) provided the project with
a $4 million loan. MES is an agency of the State Department of Natural
Resources and has authority to finance projects that preserve, improve
or manage state air, water, and land resources.
The City of Baltimore is providing the remaining $6 million for the
pyrolysis plant, and the land on which the plant is sited. The loan
from MES will be reimbursed from the proceeds received from the sale
of the steam, glassy aggregate, and the ferrous metal.
~White goods are refrigerators, washing machines, stoves, and other
household items. The ability of the plant to accept these items
(oversize bulky wastes) is a function of the shredder size and
design, not of the pyrolytic process.
**Sewage sludge was pyrolyzed in the pilot plant successfully, and this
concept may be further tested in the Baltimore project.

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Monsanto Enviro-Chem Systems, Inc., of St. Louis Mo., developed the
"Landgard"* system and operated a 35 ton per day pyrolysis pilot plant.
Monsanto also designed and, through their subsidiary, the Leonard Con-
struction Company, is building the 1,000 ton per day plant in Baltimore.
Monsanto will turn over to the City a fully operational, demonstrated
plant early in 1975.
Project Schedule
Construction is presently underway (Table 1). All development
and pilot testing work has been completed by Monsanto. Although it
is expected that the plant will operate as planned, one must be
cautioned that the data presented in this paper are based on the
experiences of the 35 ton per day pilot plant. The economics and
recovery rates are projected from those data.
TABLE 1
MAJOR PROJECT MILESTONES
Groundbreaking
Complete Design
Complete Construction
Plant Start-up
Operation and Evaluation
January 1973
January 1974
October 1974
November 1974 - February 1975
February 1975 - February 1976
SYSTEM DESCRIPTION
Original Development Work
In 1967 Monsanto began a survey of solid waste problems and their
future impact. The company, because of long experience in materials
processing, decided to concentrate on disposal methods, and investigated
various waste disposal ideas including pyrolysis. The study recognized
resource recovery as an attractive tool in solid waste management and
pyrolysis as the most attractive option. A study of pyrolysis pro-
cessing systems determined that direct-fire pyrolysis using a rotary
kiln would be the best method. A rotary kiln is a type of chamber
that is cylindrical in shape, slightly inclined, and rotates about its
*"Landgard" is the name of a proprietary system of the Monsanto Enviro-
Chem Systems, Inc. Apparatus and process patents have been allowed
by the U. S. Patent Office for the System.

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4
horizontal or lengthwise axis (item 4 in Figure 1). Solid waste enters
the high end of the kiln. Rotation tumbles the material and allows
for complete heating. Gravity slowly moves the material to the low
end for discharge. Fuel is fired directly into the kiln (hence, the
term direct-fired) rather than indirectly by heating the kiln's outer
shell, as in a popcorn popper. Rotary kilns are used extensively in
the cement industry and in processing many granulated materials.
Monsanto has designed and operated several similar units.
After a laboratory model of a direct-fire continuous pyrolysis unit
was built and operated in Dayton, Ohio, Monsanto decided to build a
pilot-size pyrolysis unit to investigate scale up data for full-size
plant design. Trial handling of mixed municipal solid waste began
near Monsanto's St. Louis plant in June 1969.
Continuous operation at a feed rate of 35 tons per day was
demonstrated by early 1970. The next year, a residue recovery system
was added to recover carbon char, glassy aggregate, and ferrous metal.
The pilot plant was dismantled in late 1971 after all testing work was
completed.
The system being built in Baltimore is a scale-up of 35 to
1,000 from this pilot plant. Scale-ups of this ratio are common
in both the petro-chemical and materials processing industries, and
no major scale-up problems are expected.
Site Description
The plant is located on a 16 acre peninsula located just south
of the Baltimore business district. The entire site is zoned indus-
trial, and the use of the site for the pyrolysis plant is consistent
with industrial redevelopment plans for the area.
Waste Types Processed
Residential and commercial solid wastes are processed. The
composition of this waste is shown in Table 2.

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FIGURE 1
BALTIMORE RESOURCE RECOVERY PLANT




Receiving 6.
Shredders 7.
Storage	8.
Reactor	9.
Afterburner 10.
Boilers
Scrubber
Plume Suppressor
Residue Separator
Glassy Aggregate
Carbon Char
Ferrous Metal
Steam Line

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6
TABLE 2
WASTE COMPOSITION
Kinds of Materials	Percent of Total
(At Plant Input)
Paper	38
Glass	10
Metals	10*
Ferrous	8
Aluminum	1*
Other	1*
Plastics	4
Rubber and Leather	3
Textiles	. 2
Wood	4
Food Wastes	14
Yard Wastes	14
Misc. Inorganics		1.
100
CHEMICAL ANALYSIS
(PERCENT)
Proximate Analysis	Ultimate Analysis
(Pre-Pyrolysis)	(Post-Pyrolysis)
Moisture 21 Ferrous	7
Volatiles 45 Glass & Ash	19
Fixed Carbon 8 Water	21
Inerts 26 Carbon	25
100	Sulfur &
Nitrogen	1*
Hydrogen	3
Oxygen	24
100
* Less than
Source: Waste Composition, EPA Data. Average composition of U.S.
solid waste stream. Chemical Analysis, Monsanto pilot plant
sampling. Data were not obtained in Baltimore, but are typical
of U.S. urban solid waste.

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7
The plant accepts residential and commercial solid waste typical
to any American city. White goods, occasional tires and the like
are processed; however, automobiles and industrial wastes are excluded.
Oversized bulky or non-shreddable waste can be removed from the
system before processing by the loader operators. Automatic safety
devices will remove large, non-shreddable wastes or stop the conveyor
belt, thereby preventing damage to the processing equipment. The
flow through the plant is illustrated in Figure 2.
Capacity
The receiving and shredding system is designed to process 1,000
tons of solid waste a day working a 10 hour shift. The pyrolysis
reactor, material recovery, and steam generator subsystems will
operate continuously 24 hours per day, seven days per week. In order
to feed the reactor continuously from this intermittent preparation
stream, a 2,000 ton storage bin is provided.
Receiving Area
Raw solid waste is discharged from conventional collection vehicles
into a concrete pit* in the receiving building. The collection trucks
are weighed prior to and after dumping. Two bulldozers push the solid
waste onto separate conveyors each leading to the shredders. The
conveyors are located at the opposite ends of the receiving pit and
elevate the waste from below floor level in the pit to the top of
the shredders.
Shredders
Mixed municipal solid waste is a very heterogeneous commodity.
However, most materials processes require a reasonably homogeneous
feed. Shredding the waste homogenizes the material, reduces odors,
and makes handling easier. The waste is fed into the two hammermill
shredders. In these machines**, 30 large hammers swing on pins
attached to the horizontal shaft and grind or mill the waste against
steel grates until the waste is shredded into 4 inch particles that
are small enough to fall through the grates. The milled refuse
exits the bottom of the shredders onto a conveyor and proceeds
to the storage bin or directly to the kiln.
The receiving pit is 160 feet long, 80 feet wide, and 14.5 feet
deep, and will hold 1,000 tons of refuse, at 270 pounds per cubic
yard density.
The shredders are manufactured by Jeffrey Manufacturing Company,
Columbus, Ohio. Each has a rotor (shaft, pins and hammers) that
is 73 in. in diameter and 99 in. long, and is belt driven by a
900 horsepower electric motor.

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FIGURE 2
PROCESS FLOW DIAGRAM
CLEAN AIR TO
ATMOSPHERE
GAS
SCRUBBER
STACK
STEAM
AFTERBURNER
WASTE HEAT
BOILER •
FAN
WATER CLARIFIER
GASES
SHREDDING
KILN
RESIDUE
STORAGE
RECEIVING
— MAGNET
WATER	_
QUENCHING ~
FERROUS
;olids
RAMFEEDER
METAL

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9
Storage Bin
Shredded municipal solid waste is difficult to store. It conveys
easily but once piled up, it tends to densify and stick together. A
2,000 ton conical, live bottom, Atlas storage bin was chosen to
store the shredded waste. This device was originally developed for
agricultural products but handles solid waste well. A similar storage
bin has been used successfully at the St. Louis energy recovery project.
The shredded waste enters the top of the bin and forms a conical
pile. A rotating drag line with buckets at the bottom of the pile
undercuts the pile and drags the material to a conveyor under the floor
of the bin. The storage bin effectively isolates the dumping,
loading, and shredding operations from the downstream processes and
acts as a buffer to absorb minor process interruptions while firing
continuously into the pyrolytic reactor (kiln).
Reactor Feed
The shredded waste is conveyed from the storage bin at a constant
rate and fed into the reactor by twin hydraulic rams.
Pyrolytic Reactor
The pyrolysis reaction takes place in a refractory lined horizontal
rotary kiln* having a throughput of 42 tons per hour.
The refractory lining, a concrete-like material, keeps the heat
of reaction within the kiln and prevents erosion of the kiln shell.
The heat required to accomplish the pyrolysis reaction is provided by
both the partial burning of the solid waste and a supplemental fuel.
A portion of the solid waste is combusted using 40 percent of the air
theoretically required for complete combustion. Number 2 heating oil,
at the rate of 7.1 gallons per input ton of waste, provides the
remainder of the required heat. The fuel oil burner is located in the
discharge end of the kiln. Pyrolysis gases move counter-current to
the waste and exit the kiln at the feed end. The gas temperature is
controlled to 1200F and the residue is kept below 2000F to prevent
slagging. If the temperature of the residue is above 2000F, the glass
will melt and stick to the metal, and all the residue would become
one dense mass that would require crushing for further processing.
The kiln is 19 feet in diameter, 100 feet long and rotates at
approximately 2 revolutions per minute.

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Energy Recovery
The pyrolytic gases (Table 3) leave the kiln and go to the after-
burner (gas purifier) where they are combusted with additional air.
The gases, which have a heat content of about 120 British Thermal Units
(BTU) per dry standard cubic foot, are allowed to burn to completion.
TABLE 3
PYROLYTIC GASES
(Percent by Volume, Dry Basis)
Nitrogen	69.3
Carbon Dioxide	11.4
Carbon Monoxide	6.6
Hydrogen	6.6
Methane	2.8
Ethylene	1.7
Oxygen	1.6
The combustion temperature is in the range of 1400F to assure efficient
and complete burning. The heat released from burning the gases is
directed into two waste heat boilers (heat exchangers), operating
in parallel, which generate 200,000 pounds of steam per hour.
Exhaust Gas System
After exiting the boilers, the waste gases are cleaned of
particulate matter in a water spray unit called a scrubber. The
scrubbed gases then pass through an induced draft fan which provides
the force for drawing the gases through the entire system. The gases,
saturated with moisture, are passed through a dehumidifier where they
are cooled (by ambient air). The water thus removed is recycled.
The dehumidified, cooled gases are then combined with ambient air
that has been heated and discharged to the atmosphere. This process
suppresses the formation of steam plumes.
Solids are removed from the scrubber water system by diverting
part of the recirculated water to a thickener, a tank were the solid
material is allowed to settle out. Flocculent (chemicals that cause
the suspended solids to lump together and settle quickly) is added
in the thickener to aid in solids removal. The clarified thickener
overflow is recycled to the scrubber while the underflow stream contain-
ing the settled solids is used as coolant in the residue quench tank.
The cooler-scrubber water system is a closed loop requiring very

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little make up water. The plant is designed to allow the afterburner
gases to bypass either or both of the boilers and enter the scrubbing
tower directly. This feature allows the plant to dispose of solid
waste during boiler outages, or at times when less than design amounts
of steam are required.
Materials Recovery
The hot residue is discharged from the kiln into a water filled
quench tank. A conveyor dewaters and elevates the wet residue from
the quench tank into a flotation separator. The light material, carbon
char, floats off as a slurry and is thickened and filtered to remove
the water. Clarified water and filtrate are recirculated within the
plant's closed-loop water system. The wet (50 percent moisture) carbon
char will be disposed of in a land disposal site until firm markets
for the material are developed. (See Product Description and Marketing
section.) The remaining heavy material (sink fraction) from the
bottom of the flotation separator is conveyed to a magnetic separator
where the ferrous metals are removed. The ferrous (iron) material
is deposited into containers for shipment to a scrap user. The
balance of the heavy material is about 65 percent glass. This material,
called glassy aggregate, passes through screening equipment with 0.5
inch openings and is then stored on-site. This glassy material will be
used as aggregate in the bituminous concrete products (often called
"glassphalt") used to pave the City's streets.
Redundancy
Waste generation will continue whether the processing plant is
able to operate or not; therefore, a standby disposal system or redun-
dant processing line is required. For short periods of system down-
time, the three day storage capacity of the dump pit and storage bin
will be put to use. The plant is designed with a quick repair capa-
bility. There are many installed spares, and changeover will take
minimum time. All equipment is designed to be repairable or rebuildable
within three to five days. Even the kiln's refractory lining could
be replaced within this short down-time. The two waste shredders are
operated in parallel, each with the capacity of 50 tons per hour. The
shredders operate independently. Either could feed the plant, at a
lesser throughput or longer shift hours.
Energy Balance
As with any energy system, the energy balance sheet is of
prime importance in determining overall system efficiency and
effectiveness. A solid waste disposal system can be either energy

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consumptive, neutral, or energy producing, depending on system
design and technology. In choosing pyrolysis as a technology, a
net energy gain was expected.
The data in Table 4 reflect the energy inputs and outputs of
the system, and also show the total material balances of the system.
In making the calculations, the following assumptions were used:
a.	Electrical power required to process one ton of waste
was determined by using quoted electrical equipment
ratings, by estimating how long each piece of equipment
would have to operate to process one ton of waste, then
by converting to BTU's assuming 30 percent conversion
efficiency from fossil fuel.
b.	Number 2 fuel oil needed to pyrolyze the waste is fed
at 7.1 gal. per ton.
c.	The waste has 4600 BTU per pound of heat value.
d.	Fuel required by the two bulldozers is 16 gal. per hour.
e.	Fuel used by other internal combustion engine vehicles
is 10 gal. per day (crane, loader, etc.).
The calculations are only approximate and are based on scale-up
factors and engineering estimates. The results show a 51 percent
plant efficiency (output energy divided by input energy). A 51 percent
efficiency is relatively good compared to other utility plants (fossil
fuel steam or electric, nuclear, water wall incinerator, etc.). The
point of this discussion is to emphasize that solid waste can replace
other expensive or depletable energy sources in an efficient manner. It
would require 670 pounds of coal or 46 gallons of oil to produce the
same amount of steam that this plant will produce from one ton of solid
waste. No attempt was made to compute the energy savings realized by
recycling the recovered iron or aggregate.
PRODUCT DESCRIPTION AND MARKETING
Steam
The transportation of steam over great distances is uneconomical.
Thus, a market for steam must be close by. Such a market exists in
Baltimore. Steam generated at the rate of 200,000 pounds per hour is
transported in a 4,500 ft. steam main to an existing Baltimore Gas
and Electric Company (BG&E) steam distribution line. It will be used
in district (downtown area buildings) heating and cooling.

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TABLE 4
ENERGY AND MATERIAL BALANCES
(T/t - Ton of Material Per Ton of Solid Waste Input)
(BTU/t - Million BTU's Per Input Ton)
INPUTS
LOSSES
OUTPUTS
Waste Feed
1 Ton
9.2 BTU/t
Combustion Air
5.02 T/t
0 BTU/t
>
>
Burner Air and "Fuel
0.43 T/t
1.0 BTU/t
Water
2.66 T/t
0 BTU/t
Electric Power
0 T/t
0.761 BTU/t
Equipment Fuel
0 T/t
0.024 BTU/t
>
>
Heat Recovery
Boiler
Pyrolysis
System
Materials Recovery
System
Exhaust
6.13	T/t
2.14	BTU/t
(To Scrubber)-^
Boiler Blow Down
i and Heat Loss
• 0.26 T/t
1 0.24 BTU/t	
Reactor Heat
0 T/t
0.83 BTU/t
Residue Peat
1.43 BTU/t
* .785 BTU/t Converted to Mechanical
Energy.

Steam
4 T/t
56 BTU/t
<
Materials
Iron
0.07 T/t
Char
0.08 T/t
Aggregate
0.17 T/t
TOTAL
9.11 T/t
10.985 BTU/t
>
TOTAL
6.39 T/t
5.425 BTU/t
L_	<
TOTAL
2.72 T/t
5.56 BTU/t

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u
BG&E has entered into a five year contract to purchase the steam
from the pyrolysis plant at the price of $.81 per 1,000 pounds of
steam based on the cost of $3.70 per barrel of Number 6 heavy fuel
oil as delivered to the buyer. For each $1 per barrel increase in
the cost of Number 6 oil, the price of steam is raised about $.22. As
the cost of fuel oil has more than doubled since the contract was signed,
the revenues expected from the steam have greatly increased. The steam
will be delivered to the BG&E line at between 100 and 260 pounds per
square inch, at a temperature not to exceed 415F, and at a rate that
does not fluctuate more than 15 percent*. During the months of July
and August only 100,000 pounds per hour will be delivered.
Ferrous Metal
About 70 tons of ferrous metal are magnetically separated from
the pyrolysis reactor residue each day. The iron is clean and reason-
ably free of contaminants (Table 5) and can be used either as melting
stock for the steel and foundry industry, or as precipitation iron in
the copper industry. The ferrous fraction could be used by a detinner
if it is recovered before pyrolysis. Provisions have been made in the
processing line to move the ferrous separation point in advance of
the pyrolytic reaction. This provision will be tested after the plant
is on line.
TABLE 5
FERROUS METAL QUALITY
Bulk Density
Iron
Contaminants
35 pounds per cubic foot
98.85% by weight
1.15% by weight
Chemical Analysis of Ferrous Metal
from Pyrolysis (Percentage)
Iron
98.850
Antimony
-
.020*
Tin
.153
Sulfur
-
.016
Carbon
.150
Phosphorus
-
.015
Copper
.150
Cobalt
-
.010*
Nickel
.140
Molybdenum
-
.010*
Lead
.088
Titanium
-
.010*
Manganese
.048
Vanadium
-
.010*
Silica
.045
Aluminum
-
.001*
Chromium
.035
Other
-
.249
* Less than
The boilers are designed to limit the solid content of the steam to
3 parts per million or less; and feed-water treatment will maintain
the ph of the steam condensate between 6.8 and 9.0.

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15
The market available for the ferrous fraction will determine the
process that must be used in removing the iron from the waste stream.
There are three basic markets for the iron in solid waste. They are:
the copper precipitation industry, the detinning industry, and the
steel industry. Each one of these markets require different charac-
teristics of the iron fraction. For instance, the detinning industry
requires tin cans that are not balled up or crushed, but rather shredded
or open so that a large surface is available for the detinning chemicals
to work properly. The copper industry also needs an open can but that
has been detinned by some process, either thermal or chemical. On the
other hand, the steel industry wants a tin and copper free iron that
is dense (crushed, shredded, or balled).
The Metal Cleaning and Processing -Company has contracted to buy
the post-pyrolysis ferrous fraction for 38.6 percent of the weekly
quoted price on Number 2 Bundles as listed on the Philadelphia Market
in Iron Age Magazine. This iron will be used for steel mill feed stock.
A glassy residue is recovered from the sink fraction of the
flotation unit. This material is relatively metal free (Table 6)
and will be used in road construction. Baltimore tested this
material (obtained from the pilot plant) as an aggregate in bituminous
paving mixtures (asphalt), in both a laboratory and on a section of
a street in the city. The results were promising and the City is
planning full scale street use once the material is available. City
street construction specifications will be revised to allow or to
require the use of this material as aggregate in binder course mixes
for City streets. Is is anticipated that the glassy aggregate will
have a value of $2 per ton at the plant site.
Glassy Aggregate
TABLE 6
GLASSY AGGREGATE ANALYSIS
Bulk Density
150 pounds per cubic foot
Composition
Percent
Glass
Rock & Misc.
Ferrous Metal
Non-Ferrous Metal
Carbon
65
28
3
2
2

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Carbon Char
The last output of the plant is a carbon char residue. It is the
float fraction of the flotation unit and is generated at the rate of
80 tons per day. The properties of this materials are shown in
Table 7.
TABLE 7
CARBON CHAR ANALYSIS
Bulk Density
Moisture Content
Heating Value, Dry Basis
20-50 pounds per cubic foot
50% per pound
7,000 BTU per pound
Analysis, Dry Basis
Component	Percent
Carbon
Ash and Glass
Volatiles
Sulfur
50.0
45.8
4.0
0.2
Extract Analysis
Component
Percent or Parts Per
Sodium
over 30%
Calcium
0.1-1.0%
Copper
0.03-0.3%
Magnesium
0.03-0.3%
Potassium
0.03-0.3%
Boron
0.01-0.1%
Strontium
0.001-0.1%
Iron
0.001%*
Molybdenum
0.001%*
Silicon
0.001%*
Phosphorus
25 ppm*
Chromium
10 ppm*
Lead
10 ppm*
Tin
10 ppm*
Vanadium
5 ppm*
Zinc
5 ppm*
Aluminum
1 ppm*
Cadium
1 ppm*
Manganese
1 ppm*
Silver
1 ppm*
Titanium
1 ppm*
(PPM)
* Less than

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Two possible uses for the char are:
a.	As a substitute for coinmercial activated carbon for waste
water treatment plants. Laboratory experiments have
substantiated the absorption characteristic of carbon char,
and further research on carbon slurry absorption is scheduled.
b.	As a soil conditioner along with dried and digested sewage
sludge. This use will be tested in Baltimore. The char
could be mixed with the City's sludge, dried, and given to
the public at no charge.
However, until a good market for the char is developed, it will be
disposed of in a landfill.
ECONOMICS
The economics of the pyrolysis plant is only an estimate at
this stage of the project. In addition, it should be noted that the
data presented below are very site specific. It would not be advisable
to assume that these figures are automatically applicable to other
locations without a prior study of pertinent factors such as site
costs, labor and material costs, product marketability, plant size,
etc. No attempt has been made to normalize these figures to make
them applicable to other areas of the country except for the method
of capital amortization. Since the Baltimore situation is unique
because an EPA Grant and an MES loan are applied to the capital cost
of the plant, Baltimore's actual amortization costs have not been
presented. Instead, a typical 20 year, 6 percent municipal bond
was used to determine capital cost figures.
Table 8 presents the capital and operating cost and revenues of
the plant. Plant throughput, based on 85 percent availability, will
be 310,000 tons per year, and all costs and revenues have been con-
verted to dollars per ton. A comparison is shown between anticipated
economics of January 1974 and those of February 1974 to illustrate
the effect of inflation. With the escalating cost of fossil fuel,
an energy recovery plant has a good possibility of operating at a break
even point, and could make a profit for a city.

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TABLE 8
ECONOMICS
($ Per Throughput Ton)
Amortization*
Operating Costs
Fuel
Electricity
Manpower
Water and Chemicals
Maintenance
Miscellaneous
Char Removal
Total
Total Expenses
Revenues
Steam**
Iron
Glassy Aggregate
Total Revenues
Net Operating Cost
January 1973
$4.34
$ .89
1.06
1.02
.31
1.84
.42
.18
$3.89
.44
.34
$5.72
$10.06
$4.67
$5.39
February 1974
$5.55
2.20
1.50
1.10
.30
1.90
.40
.20
$11.18
1.55
.40
$7.60
$13.15
$13.13
$ .02
* Approximated Plant Cost:
January, 1973	$16 million
February, 1974	$20 million
** Steam Revenues:
January, 1973	$3.70 per barrel fuel oil
February, 1974 $10.63 per barrel fuel oil

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ENVIRONMENTAL CONSIDERATIONS
Environmental Advantage
No pyrolysis system for solid waste has as yet operated at full
scale. One of the objectives of the resource recovery grant is to
demonstrate whether this system can recover the energy and material
resources in municipal solid waste without polluting the environment.
The success of the plant will:
1.	Allow BG&E Co. to save 15 million gallons of oil annually.
2.	Permit the City to dispose of much of its solid waste with
lower air emissions than is presently possible.
3.	Cause steam to be produced with lower emissions than
can be produced from existing boilers.
4.	Enable industry to use recovered materials instead of
depletable virgin materials in new products, to conserve
resources, and save energy.
Air Emissions
Once the plant is operational, Baltimore will be able to close
down one existing incinerator that does not meet clean air standards.
Air emissions from the pyrolysis plant will meet the Federal particulate
emission standard of .08 grains per standard cubic foot of dry flue
gas corrected to 12 percent CO2, and the Maryland code of .03 grains
per standard cubic foot. As there is very little sulfur in solid
waste, the sulfur dioxide emissions from the plant are correspondingly
low, in the under 100 parts per million range. Nitrogen oxide (NO )
production in the plant is also kept at a low level by combusting the
pyrolysis gases at a low temperature. The N0x emissions are in the
range of less than 50 parts per million. Unburned hydrocarbons in
the exhause are held to just a few parts per million of methane
equivalent. The emission quality is guaranteed by the contractor.
Moreover, the plant will be closely monitored, as a part of the EPA
evaluation, to assure that all applicable local, state, and Federal
point source and ambient air quality standards are met.
Water Effluent
All process water is recycled. However, occassionally recycled
water will exceed needs and any excess water will be discharged into
the sanitary sewer at a maximum flow of 75 gallons per minute. Any
water so discharged will be treated at Baltimore's Back River Plant
and will not significantly change the influent characteristics of the
treatment plant. The Back River Plant employs both primary and
secondary treatment processes.

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Land Pollution
The only plant output that may be disposed of on land is the
carbon char. If use of this material is not possible, then it will
have to be landfilled. The char contains about one percent (Table 7)
of water soluble material and disposal will have to be engineered to
prevent the char leachate from entering the groundwater system.
Noise
Hammermilling solid waste is a noisy operation. The shredders
are located above ground in sound-proofed structures. All other
equipment that could cause noise pollution is protected. All
applicable noise regulations will be met, and ambient noise at the plant
boundaries will be within standards for this industrially zoned site.
Environmental Summary
There will be no significant adverse environmental effect from
the operation of this solid waste conversion plant. On the contrary,
if the process proves successful, the City can reduce total pollution
associated with present practices of landfilling, incineration, use of
iron ore in steelmaking, and use of fossil fuels to generate steam.
GUARANTEE
Monsanto is responsible for the complete design, construction
and start-up of the plant, all at a fixed price. The contract calls
for Monsanto to turn over to Baltimore a completely operational
"turnkey" facility. Additionally, the contract provides for up to
?4 million in performance penalities if the plant fails to meet
any of the following standards:
1.	Air emissions will meet existing Federal, State, and local
air pollution regulations.
2.	Plant capacity will average a minimum of 85 percent of
design capacity for an identified 60 day period.
3.	Putrescible content of residue will be less than 0.2
percent.

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PROJECT EVALUATION
The pyrolysis plant will be technically, economically, and
environmentally evaluated by an independent contractor hired by EPA
during the first year of operation, and the results will be disseminated
to the public. Each processing step will be evaluated to determine
its ability to meet the original design requirements, its operation
and maintenance costs, its economic balance, its energy balance, and
so forth. Plant effluents and products will be analyzed to make sure
they meet design specifications and environmental acceptability.
An interim report will be published in the Fall of 1975. A
final report will be published in late 1976.
Once operational, the plant will be open to the general public.
For information about visiting hours and tour arrangements, contact
Mr. Elliot Zulver, Project Officer, Bureau of Utility Operations,
900 Municipal Building, Baltimore, Maryland 21202.

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QUESTIONS AND ANSWERS
1-Q:	Our city has a separate newspaper collection. How would that
affect a pyrolysis plant?
A: Removing newspapers from the waste stream for recycling is an
environmentally economically sound technique in resource
recovery and is a recommended approach to be used in conjunction
with an energy recovery plant. Removing the newsprint prior to
pyrolysis will reduce the total tonnage and BTU content of the
waste, but generally only by a small percentage. (See
Recommended Reading).
2-Q:	What if there is no market for steam in our city? Can we still
use a gaseous pyrolysis system?
Ar The lack of a market for steam has severely limited solid-waste-to-
steam-projects. However, provisions in the design of the Baltimore
project have alleviated this constraint. Monsanto feels that the
pyrolysis gas can be cleaned and piped a short distance to an
industrial or utility boiler and burned along with the normally
used fossil fuel. Another option proposed by Monsanto is to
use the steam to generate electricity on site.
3-Q:	What would happen to a Baltimore-type system if source reduction
measures are implemented, like banning the throwaway beverage
container?
A: If throwaway beverage containers are eliminated from the input
feed of this plant, there would be a small reduction in the non-
combustible fraction of the waste. The ferrous fraction would
probably be cut in half, and the volume of glassy aggregate would
be correspondingly reduced, but the overall economics of the
plant would still be viable. Revenue would be reduced, but as
energy production is the primary money-maker, the reduction
would not be appreciable. The energy savings from eliminating
throwaways would far overshadow the slight drop in revenue.
Although, the energy savings may not directly affect the City,
the loss of revenues would. If many source reduction measures
were adopted, like reduction of packaging waste, the 1,000 ton
per day plant would have to draw waste from a larger population
base to generate the design throughput.
4-Q:	If new resource recovery technology is developed in the next
few years, won't Baltimore have an obsolete plant?

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A: In our technological society, things uecome obsolete quickly;
however, they remain useable. The Baltimore plant has a 15 to 20
year useful life. After that time, if new and better technology
is available, it will probably be used. In the meantime, we must
move ahead with the best available technology, now.
5-Q: We have about five years of life remaining in our landfill. Why
should we worry about resource recovery now?
A: You should be planning now. The lead time on a resource recovery
facility is from three to five years. Make decisions now: plan
for alternate disposal methods before you become buried in your
own waste.

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2 A
RECOMMENDED READING
The following publications are available from:
Energy Recovery Program
Resource Recovery Division (AW-563)
Office of Solid Waste Management Programs
U. S. Environmental Protection Agency
Washington, D. C. 20460
1.	Energy Conservation Through Improved Solid Waste Management
by Robert A. Lowe, with appendices by Michael Loube and
Frank A. Smith.
2.	Energy Recovery from Waste by Robert A. Lowe.
3.	Markets and Technology for Energy Recovery from Solid Waste
by Steven J. Levy.
4.	Pyrolysis by Steven J. Levy.
5.	List of Pyrolysis Companies by Robert Holloway.
6.	Effect of Removing Paper on the Energy Value of Solid Waste
by Robert Holloway.
CPO 888-977

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