BALTIMORE DEMONSTRATES GAS PYROLYSiS ------- ------- BALTIMORE DEMONSTRATES GAS PYROLY5IS resource recovery from solid waste This 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 1975 ------- An environmental protection publication (SW-75d.ij in the solid waste management series Mention of commercial products or organizations does not constitute endorsement by the U.S. Government For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 ------- foreword The solid waste generated each year by urban areas in the United States contains an estimated 830 trillion Btu of energy—the equivalent of 400,000 barrels of oil per day, which is nearly a third of the Alaskan pipeline's pro- jected flow. In addition to energy, 7 percent of the iron, 8 percent of the tin, and 14 percent of the paper consumed each year could be supplied from what is now waste. At present, despite concern about shortages of energy and materials, less than 1 percent of the resources in municipal waste is being re- claimed; the rest goes into dumps, landfills, and incinerators. Large-scale recovery of usable waste materials would not only conserve re- sources but also save the environment from much of the pollution, hazards to health, and blight caused by improper disposal. The increasingly burdensome cost of disposal in urban areas is another reason to urge reuse. And informa- tion is emerging to show that recycling has other benefits that are not so ap- parent. When two production systems are compared, one using virgin mate- rials, the other waste materials, the system using wastes almost always causes less air and water pollution, generates less solid waste, and consumes less energy. These differences appear when the environmental impacts of all activities are measured—mining, processing, fabricating, manufacturing, and the transportation and disposal steps in between. The Nation's task, then, is to mobilize our systems and institutions to- ward recovering and using the resources in waste. One tool that should facil- itate that movement is new technology. But technological advances are usual- ly expensive and entail risk. The Resource Recovery Act of 1970 (which amended the Solid Waste Disposal Act of 1965) enabled the Federal solid waste management program to assist States and municipalities by assuming part of the risk of trying new technologies. The result was a significant ex- pansion of the Federal resource recovery demonstration program. This report describes one project in that program, in which energy will be recovered in the form of steam by converting solid waste into a combustible gas through pyrolysis and then using the gas as a fuel to fire a steam boiler. Ferrous metals will be recovered from the pyrolysis residue, as well as a glassy aggre- gate for use in street construction and a carbon char that has possible uses in wastewater treatment and soil conditioning. The process was developed on a pilot scale by Monsanto Enviro-Chem Systems, Inc., St. Louis, Missouri. In July 1972, the City of Baltimore applied to the U.S. Environmental Protection Agency for a grant to demon- strate this Monsanto "Landgard" system with a full-scale pyrolysis plant that ill ------- would process about half of the city's solid waste. The grant that was awarded covers 40 percent of the cost of the project. Construction began in early 1973 and operation is scheduled to begin in early 1975. The Baltimore project will recover energy and materials from waste, relieve the city's disposal problem, and have beneficial effects on the environment. The projected costs and revenues indicate a good possibility that the plant can do all this at a cost competitive with or lower than that of landfilling or incineration. This demonstration exemplifies the kind of creative solutions that gov- ernment 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 IV ------- BALTIMORE DEMONSTRATES GAS PYROLY5IS resource recovery from solid waste 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 5 years, however, more sophisticated solid waste incinerators 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. Second, the 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 a demonstration with financial support from the U.S. Environmen- tal Protection Agency's Office of Solid Waste Management Programs. The project is scheduled to begin processing waste in early 1975. Objectives The primary objective of the project is to demonstrate the technical and economical feasibility of recovering energy from mixed municipal waste using 1 ------- a gaseous pyrolysis process. (Pyrolysis is the physical and chemical decompo- sition of organic matter brought about by the action of heat in an oxygen- deficient atmosphere.) The City of Baltimore is building a full-size, 1,000-ton- per-day plant that will receive mixed municipal solid waste, including krge household appliances and tires. Sewage sludge may also be included. The Baltimore 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 incoming waste into usable products in ways that will meet all pollution control standards. Approximately half of Baltimore's residential solid waste will be processed by this plant. 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 half of the city's residential solid waste 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 less than that of landfilling and incineration, according to a pre- liminary economic analysis. Participants 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 the State's 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 ferrous metal. Monsanto Enviro-Chem Systems, Inc., of St. Louis developed the "Landgard"* system and operated a 35-ton-per-day pilot plant. Monsanto also designed and, through their subsidiary, the Leonard Construction Com- *Landgard is a proprietary system; apparatus and process patents have been allowed by the U.S. Patent Office. ------- 1. RECEIVING 2. SHREDDERS 3. STORAGE 4. REACTOR 5. AFTERBURNER 6. BOILERS 11. CARBON CHAR 7. SCRUBBER 12. FERROUS METAL 8. PLUME SUPPRESSOR 13. STEAM LINE 9. RESIDUE SEPARATOR 10. GLASSY AGGREGATE Figure 1. Artist's sketch of the Baltimore plant. pany, 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. Schedule Construction is presently underway. All development and pilot testing work has been completed by Monsanto. The major dates on the project schedule are: Groundbreaking Complete design Complete construction Plant start-up Operation and evaluation January 1973 January 1974 December 1974 January to March 1975 April 1975 to April 1976 Although it is expected that the plant will operate as planned, the reader should be aware that the data presented in this report are based on the experiences of the 35-ton-per-day pilot plant. The economic estimates and recovery rates are projected from those data. ------- 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 ideas, including pyrolysis. They perceived resource recovery as an attractive tool in solid waste management and pyrolysis as the most attractive option. A study of pyrolysis processing systems determined that direct-fire pyrolysis using a rotary kiln would be the best method. A rotary kiln is a cylindrical chamber, slightly inclined, that rotates about its horizontal or lengthwise axis. Solid waste enters the high end of the kiln. Fuel is fired directly into the kiln (hence, the term direct-fired) rather than burned to heat the kiln's outer shell as with a popcorn popper. Rotation tumbles the material and allows for complete heating. Gravity slowly moves the material to the low end for dis- charge. Rotary kilns are used extensively in the cement industry and in pro- cessing 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 near St. Louis to develop scale-up data for designing a full-size plant. Trial handling of mixed municipal solid waste began in June 1969. GAS SCRUBBER STEAM / RECEIVING CLEAN AIR TO ATMOSPHERE I STAC FAN WATER CLARIFIER RESIDL MAGNET WATER QUENCHING -9- FERROUS METAL Figure 2. The processing at the Baltimore plant is depicted in this flow diagram. ------- Continuous operation at a feed rate of 35 tons per day was demonstrated by early 1970. The next year, a system was added to recover carbon char, glassy aggregate, and ferrous metal from the residue. The pilot plant was dis- mantled in late 1971 after all testing was completed. The system being built in Baltimore is a scale-up to 1,000 tons per day from the 35-ton pilot plant. Scale-ups of this ratio are common in both the petrochemical and materials processing industries, and no major scale-up problems are expected. The Site The plant is located on a 16-acre peninsula just south of the Baltimore business district. The entire site is zoned industrial, and its use for the pyrol- ysis plant is consistent with industrial redevelopment plans for the area. Waste Types Processed The plant will accept residential and commercial solid waste typical of U.S. cities (Table 1). Large household appliances, occasional tires, and the like will be processed; however, automobiles and industrial wastes are ex- cluded. The ability of the plant to accept bulky items is a function of the shredder size and design, not of the pyrolytic process. Oversized or non- shreddable waste can be removed from the system before processing by the loader operators. Automatic safety devices will remove large, nonshreddable wastes or stop the conveyor belt, thereby preventing damage to the processing equipment. Sewage sludge was pyrolyzed successfully at the pilot plant; this practice may be further demonstrated in the Baltimore project. Capacity The receiving and shredding system is designed to process 1,000 tons of solid waste during a 10-hour daily shift. The pyrolysis reactor, materials recovery, and steam generator subsystems will operate continuously 24 hours per day, 7 days per week. In order to feed the reactor continuously from the intermittent preparation stream, a storage bin with a capacity of 2,000 tons 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 for purposes of billing and determining the ton- nage processed. Two bulldozers push the dumped waste onto two separate ------- TABLE 1 Composition of Municipal Solid Waste4 Kind of material Percent of incoming waste Paper Glass Metals Ferrous Aluminum Other Plastics Rubber and leather Textiles Wood Food wastes Yard wastes Miscellaneous inorganics 8 It It 38 10 10t 4 3 2 4 14 14 1 100 Chemical analysis Proximate analysis (pre-pyrolysis) Ultimate analysis (post-pyrolysis) Component Moisture Volatiles Fixed carbon Inerts Percent 21 45 8 26 100 Component Percent Ferrous 7 Glass and ash 19 Water 21 Carbon 25 Sulfur and nitrogen It Hydrogen 3 Oxygen 24 100 *Sources: Percentages of kinds of materials are from EPA study of typical composi- tion of U.S. municipal solid waste streams. The chemical analysis is based on samples taken at the Monsanto pilot plant in St. Louis. fLess than percent shown. ------- conveyors that lead to the shredders. The conveyors are located at opposite ends of the receiving pit and elevate the waste from below floor level in the pit to the top of the shredders. The receiving pit is 160 feet long, 80 feet wide, and 14.5 feet deep, and will hold 1,000 tons of refuse at a density of 270 pounds per cubic yard. Shredders Mixed municipal solid waste is very heterogeneous. Most materials-conver- sion processes require a reasonably homogeneous feed, however. Shredding the waste homogenizes it, reduces odors, and makes handling easier. Each of the two hammermill shredders at the Baltimore plant contains 30 large ham- mers that swing on pins attached to a horizontal shaft. They grind or mill the waste against steel grates until the particles are small enough (4-inch diameter) to fall through the grates. The milled refuse falls onto a conveyor that trans- ports it to the storage bin or directly to the kiln. The shredders are manufactured by Jeffrey Manufacturing Company, Columbus, Ohio. Each has a rotor (shaft, pins, and hammers) that is 73 inches in diameter and 99 inches long, and is belt-driven by a 900-horse- power electric motor. Storage Bin and Reactor Feed Shredded municipal solid waste is difficult to store. It is conveyed easily, but once piled up, it tends to stick together and become dense. A conical, live-bottom, Atlas storage bin with a 2,000-ton capacity 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 another EPA-supported energy recovery project, located in St. Louis. 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; it acts as a buffer to absorb minor process inter- ruptions so that the waste can be fired continuously into the pyrolytic reactor (kiln). 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 with a throughput of 42 tons per hour. The kiln is 19 feet in diameter, ------- Figure 3. The pipeline will transport steam, the plant's major product, to Balti- more Gas & Electric's steam distribution line. The structure at center of photo houses 100 feet long, and rotates at approximately 2 revolutions per minute. The concrete-like refractory lining 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. No. 2 heating oil, at the rate of 7.1 gallons per ton of waste, provides the re- mainder 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 1,200 F and the residue is kept below 2,000 F to prevent slagging. If the temperature of the residue goes above 2,000 F, the glass particles will melt and stick to the metal, and all the residue would become one dense mass that would require crushing for further processing. Energy Recovery The pyrolytic gases leave the kiln and go to the afterburner (gas purifier) where they are combusted with additional air. The gases, which have a heat ------- the rams for feeding the shredded waste into the kiln as it is conveyed from the storage bin. content of about 120 British thermal units (Btu) per dry standard cubic foot, consist of the following: Nitrogen Carbon dioxide Carbon monoxide Hydrogen Methane Ethylene Oxygen Percent by volume, dry basis 69.3 11.4 6.6 6.6 2.8 1.7 1.6 The combustion temperature is in the range of 1,400 F 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 re- moved 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 where 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 containing the settled solids is used as coolant in the residue quench tank. The cooler-scrubber water system is a closed loop re- quiring very little makeup water. The plant is designed to allow the after- burner 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 the demand for steam is low. Materials Recovery The hot residue is discharged from the kiln into a water-filled quench tank. A conveyor dewaters the wet residue and elevates it from the quench tank into a flotation separator. A 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 per- cent moisture) carbon char will be disposed of in a land disposal site until firm markets for the material are developed (see section on The Products and Their Marketing). The remaining heavy material (sink fraction) from the bot- tom of the flotation separator is conveyed to a magnetic separator where the ferrous metals are removed and 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, is passed through screens with Vi-inch open- ings and then stored on-site. This glassy material will be used as aggregate in the bituminous concrete product (often called "glassphalt") used to pave the city's streets. Figure 4. The large structure in the foreground is the scrubber for cleaning the waste gases coming out of the boilers. Figure 5. The residue from the pyrolysis reaction is conveyed to building at left, where materials recovery processing begins. 10 ------- lit ------- Redundancy Since waste generation will continue whether the processing plant is able to operate or not, a standby disposal system or redundant processing line is required. For short periods of system downtime, the 3-day storage capacity of the dump pit and storage bin will be put to use. The plant is designed with a quick repair capability. There are many installed spares, and changeover will take minimum time. All equipment is designed to be repairable or re- buildable within 3 to 5 days. Even the kiln's refractory lining could be re- placed within this short downtime. The two waste shredders are operated in parallel, each with the capacity of 50 tons per hour. Since they operate inde- pendently, either could feed the plant by itself, at a lesser throughput or over a longer shift. Figure 6. The Baltimore plant's energy and material balances have been esti- mated. In energy efficiency this plant is expected to compare well with other types of utility plants. 12 ------- Energy Balance As with any energy system, the energy balance sheet is of prime impor- tance in determining overall system efficiency and effectiveness. A solid waste disposal system can be either energy consumptive, neutral, or energy producing, depending on its design and technology. In choosing pyrolysis as a technology, a net energy gain was expected. The inputs and outputs of energy and materials were calculated using the following assumptions: 1. Electrical power required to process 1 ton of waste can be deter- mined by using quoted electrical equipment ratings, estimating how long each piece of equipment would have to operate to pro- cess 1 ton of waste, and then converting to Btu assuming 30 per- cent conversion efficiency from fossil fuel. 2. No. 2 fuel oil needed to pyrolyze the waste is fed at a rate of 7.1 gallons per ton. 3. The waste has a heat value of 4,600 Btu per pound. 4. The two bulldozers use 16 gallons of fuel per hour. 5. Other internal combustion engine vehicles (crane, loader, etc.) use 10 gallons per day. The calculations are only approximate and are based on scale-up factors and engineering estimates (Figure 6). The results show a 51 percent plant effi- ciency (output energy divided by input energy). A 51 percent efficiency is relatively good compared to that of other utility plants (fossil-fuel-fired steam or electric plants, nuclear plants, waterwall incinerator, etc.); this emphasizes the point that solid waste can replace other 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 1 ton of solid waste. No attempt was made to compute the energy savings realized by re- cycling the recovered iron or aggregate. 13 ------- the products and their marketing Steam A steam-generating plant must have a nearby market because the transpor- tation of steam over great distances is uneconomical. Such a market exists in Baltimore. Steam generated at the rate of 200,000 pounds per hour is trans- ported in a 4,500-ft steam main to an existing Baltimore Gas and Electric Company (BG&E) steam distribution line. It will be used to heat and cool buildings in the downtown area. BG&E has entered into a 5-year contract to purchase the steam from the pyrolysis plant at a price of $0.81 per 1,000 pounds of steam, which is based on a cost of $3.70 per barrel of No. 6 heavy fuel oil as delivered to the buyer. For each $l-per-barrel increase in the cost of No. 6 oil, the price of steam is raised about $0.22. As the cost of fuel oil has more than doubled since the contract was signed, the revenues expected from the steam have greatly in- creased. 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 415 F, 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. The boilers are designed to limit the solid content of the steam to 3 parts per million. Feed-water treatment will maintain the pH of the steam con- densate between 6.8 and 9.0. Ferrous Metal About 70 tons of ferrous metal will be magnetically separated from the pyrolysis reactor residue each day. The iron is clean and reasonably free of contaminants (Table 2), 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, and separation of ferrous metals before pyrolysis will be tested after the plant is in operation. The market for the ferrous fraction will determine the process used in re- moving the iron from the waste stream. There are three basic markets for this iron: the copper precipitation industry, the detinning industry, and the steel 14 ------- TABLE 2 Quality of Ferrous Metal Recovered Bulk density Iron Contaminants from Pyro lysis Residue 35 pounds per cubic foot 98.85% by weight 1.1 5% by weight Chemical analysis Component Percent Iron 98 Tin Carbon Copper Nickel Lead Manganese Silicon Chromium .850 .153 .150 .150 .140 .088 .048 .045 .035 Component Percent Antimony .020* Sulfur .016 Phosphorus .015 Cobalt .010* Molybdenum .010* Titanium .010* Vanadium .010* Aluminum .001* Other .249 "Less than percent shown. TABLE 3 Analysis of Glassy Aggregate Recovered from Pyro lysis Residue Bulk density 150 pounds per cubic foot Component Glass Rock and miscellaneous Ferrous metal Nonferrous metal Carbon Percent 65 28 3 2 2 15 ------- industry. Each requires different characteristics in the scrap iron it uses. 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 needs cans that are open and that have been detinned by some process, either thermal or chemical. The steel industry wants scrap that is dense (crushed, shredded, or balled) and free of tin and copper. 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 No. 2 bundles as listed on the Philadelphia Market in Iron Age Magazine. This iron will be used for steelmill feed stock. Glassy Aggregate The glassy residue recovered from the sink fraction in the flotation unit is relatively metal-free (Table 3) and will be used in road construction. Balti- more 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 specifi- cations will be revised to allow or to require the use of this material as aggre- gate in binder course mixes for city streets. It is anticipated that the glassy aggregate will have a value of $2 per ton at the plant site. Carbon Char A carbon char residue, the float fraction from the flotation unit, is gen- erated at the rate of 80 tons per day. This material consists of 50 percent carbon (dry weight basis), with the rest mostly ash and glass (Table 4). One possible use for the char is as a substitute for commercial activated carbon used in wastewater treatment plants. Laboratory experiments have substantiated the absorption characteristic of carbon char, and further re- search on carbon slurry absorption is scheduled. Char can also be used as a soil conditioner along with dried and digested sewage sludge. This use will be tested in Baltimore. The char could be mixed with the city's sludge, dried, and given to the public at no charge. Until a good use for the char is developed, however, it will be disposed of in a land disposal site. 16 ------- TABLE 4 Analysis of Carbon Char Residue Bulk density 20-50 pounds per cubic foot Moisture content 50% by weight Heating value , dry basis 7,000 Btu per pound Analysis, dry basis Component Carbon Ash and glass Volatiles Sulfur Percent 50.0 45.8 4.0 0.2 Analysis of water-extractable fraction Component Sodium Calcium Copper Magnesium Potassium Boron Strontium Iron Molybdenum Silicon Phosphorus Chromium Lead Tin Vanadium Zinc Aluminum Cadmium Manganese Silver Titanium Percent or parts per million (ppm) over 30% 0.1-1.0% 0.03-0.3% 0.03-0.3% 0.03-0.3% 0.01-0.1% 0.001-0.1% 0.001%* 0.001%* 0.001%* 25 ppm* 10 ppm* 10 ppm* 1 0 ppm* 5 ppm* 5 ppm* 1 ppm* 1 ppm* 1 ppm* 1 ppm* 1 ppm* *Less than figure shown. 17 ------- TABLE 5 Economic Estimates for the Baltimore Plant ($ per throughput ton) Costs and revenues Amortization* Operating costs Fuel Electricity Manpower Water and chemicals Maintenance Miscellaneous Char removal Total Total expenses Revenues Steamf Iron Glassy aggregate Total revenues Net operating cost January 1973 $4.34 $ .89 1.06 1.02 .31 1.84 .42 .18 $5.72 $10.06 $3.89 .44 .34 $4.67 $5.39 February 1974 $5.55 $2.20 1.50 1.10 .30 1.90 .40 .20 $7.60 $13.15 $11.18 1.55 .40 $13.13 $ .02 *Approximate plant cost: in January 1973, $16 million; in February 1974, $20 maiion. fPrice is keyed to fuel oil price, which was $3.70 per barrel in January 1973, and $10.63 per barrel in February 1974. 18 ------- economics Data on the economics of the pyrolysis plant consist only of estimates at this time (Table 5). It should also be noted that the data are very site-specific and should not be considered necessarily applicable to other locations. Such pertinent factors as site costs, labor and material costs, product marketability, and plant size will naturally vary from place to place. No attempt has been made to normalize the figures to make them applicable to other areas of the country except in the case of capital amortization. Since the Baltimore situa- tion is unique because an EPA grant and an MES loan are applied to the capi- tal cost of the plant, Baltimore's actual amortization costs are not presented. Instead, a typical 20-year, 6-percent municipal bond was used to determine capital cost figures. Plant throughput, based on 85 percent availability, will be 310,000 tons per year, and all costs and revenues have been converted to dollars per ton. At January 1973 costs and prices, the total costs per ton are estimated to be $10.06 and total revenues $4.67, giving a net cost of $5.39. Based on Feb- ruary 1974 costs and prices, the estimates are $13.15 for total expenses and $13.13 for total revenues, giving a net operating cost of $0.02 per ton. The large difference in estimated revenues between the 2 years is mostly due to the rise in the price of steam, which is keyed to the price of fuel oil. With the escalating cost of fossil fuel, an energy recovery plant has a good possibility of operating at a break-even point, and might in fact make a profit for a city. environmental considerations One of the objectives of the Baltimore project is to demonstrate whether a pyrolysis system can recover the energy and material resources in municipal solid waste without polluting the environment. If successful the plant will: 19 ------- 1. Allow BG&E 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 is possible with existing boilers. 4. Enable industry to use recovered instead of virgin materials, thus conserving resources and saving energy. Air Emissions Once the plant is operational,. Baltimore will be able to close down an 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 will be correspondingly low, under 100 parts per million. Nitrogen oxide (NOX) pro- duction in the plant is also kept at a low level by combusting the pyrolysis gases at a low temperature. The NOX emissions will amount to less than 50 parts per million. Unburned hydrocarbons in the exhaust will be held to just a few parts per million of methane equivalent. The emission quality is guar- anteed 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 Fed- eral point source and ambient air quality standards are met. Water Effluent All process water is recycled. Occasionally recycled water will exceed needs, and such 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. 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. The char contains about 1 percent of water-soluble material, and disposal will have to be engineered to prevent the char leachate from entering the groundwater system. 20 ------- Figure 7. Operation of the entire plant is monitored and controlled from this panel. The TV screens above the panel show what is on the conveyors feeding into the shredders. Noise The hammermilling of solid waste is a noisy operation. The shredders are located above ground in soundproofed structures. All other equipment that could cause noise pollution is also protected. All applicable noise regulations will be met, and ambient noise at the plant boundaries will be within stand- ards for this industrially zoned site. Summary There will be no significant adverse environmental effect from the opera- tion of this plant. On the contrary, if the process proves successful, the city can reduce total pollution associated with present practices of landfilling, in- cineration, use of iron ore in steelmaking, and use of fossil fuels to generate steam. 21 ------- guarantee Monsanto is responsible for the complete design, construction and start-up of the plant, all at a fixed price. The "turn-key" contract calls for Monsanto to turn over to Baltimore a completely operational facility. Additionally, the contract provides for up to $4 million in performance penalties if the plant fails any of the following requirements: (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. project evaluations During the first year of operation, the pyrolysis plant will be evaluated for its technical and economic characteristics and for its environmental effects by an independent contractor hired by EPA, 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 specifications. An interim report will be published in the spring of 1976. A final report will be published in mid-1977. Once operational, the plant will be open to the general public. For infor- mation about visiting hours and tour arrangements, contact Elliot Zulver, Project Officer, Bureau of Utility Operations, 900 Municipal Building, Balti- more, Maryland 21202. questions and answers Q Our city collects newspapers separately from other waste so that the paper can be sold to wastepaper dealers. How would this reduction in the paper content of municipal waste affect a pyrolysis plant? 22 ------- A Generally the tonnage and Btu content of the waste will be re- duced only by a small percentage (see Recommended Reading). The presence of an energy recovery plant should not of itself deter a city from this environ- mentally sound practice. Wherever feasible, wastepaper should be recycled rather than used for fuel. Q What if there is no market for steam in our city? Can we still use a gaseous pyrolysis system? A The lack of a market for steam has severely limited solid-waste-to- steam projects. This pyrolysis system can be adapted so that a steam market is not necessary. 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. Q What would happen to a Baltimore-type system if measures are implemented to reduce the generation of waste, like banning the throwaway beverage container? A If throwaway beverage containers are eliminated, there would be a small reduction in the noncombustible fraction of the waste. The ferrous fraction and the volume of glassy aggregate would probably be cut in hah", but the overall economics of the plant would still be viable. Revenue would be reduced, but as energy production is the primary moneymaker, the reduc- tion would not be appreciable. The energy savings from eliminating throw- aways would far overshadow the slight drop in revenue. If many measures to reduce waste materials were adopted, however, the 1,000-ton-per-day plant may have to draw waste from a larger population base in order to operate at an economical level. Q // new resource recovery technology is developed in the next few years, won't Baltimore have an obsolete plant? A In our technological society, things become obsolete quickly; however, they remain usable. The Baltimore plant has a useful life of 15 to 20 years. After that time, if new and better technology is available, it will probably be used instead. In the meantime, we must move ahead with the best technology that is available now. Q We have about 5 years of life remaining in our landfill. Why should we worry about a resource recovery plant now? A You should be planning now. The lead time needed to get a re- source recovery facility underway is from 3 to 5 years. And there is the basic goal of conservation—we are running out of things and we should not plan to go on burying materials and energy when we have the means to recover these resources. 23 ------- RECOMMENDED READING The following publications are available from: Solid Waste Information Materials Control Section U.S. Environmental Protection Agency Cincinnati, Ohio 45268 1. Energy conservation through unproved solid waste management, by Robert A. Lowe, with appendices by Michael Loube and Frank A. Smith. Environmental Protection Publication SW-125. Cincinnati, U.S. Environmental Protection Agency, 1974. 39 p., app. 2. Energy recovery from waste; solid waste as supplementary fuel in power plant boilers, by Robert A. Lowe. Environmental Protec- tion Publication SW-36d.ii. Washington, U.S. Government Print- ing Office, 1973. 24 p. 3. Markets and technology for energy recovery from solid waste, by Steven J. Levy. Environmental Protection Publication SW-130. Washington, U.S. Environmental Protection Agency, 1974. 31 p. 4. Pyrolysis of municipal solid waste. Waste Age, 5(7): 14-15,17-20, Oct. 1974. 5. List of pyrolysis companies, by J. Robert Holloway. (In prepara- tion.) 6. The effect of paper recovery on the characteristics of solid waste as a fuel, by J. Robert Holloway and John H. Skinner. (In prep- aration.) 7. The demonstration of systems for recovering materials and energy from solid waste, by John H. Skinner. Presented at the National Materials Conservation Symposium, National Bureau of Standards, Gaithersburg, Md., Apr. 29, 1974. [Washington], U.S. Environ- mental Protection Agency, 1974. 20 p. 8. Decision-makers guide in solid waste management, compiled by Robert A. Colonna and Cynthia McLaren. Environmental Protec- tion Publication SW-127. Washington, U.S. Government Printing Office, 1974. 157 p. 9. Recovering resources from solid waste using wet-processing; EPA's Franklin, Ohio, demonstration project, by David G. Arella. Environmental Protection Publication SW47d. Washington, U.S. Government Printing Office, 1974. 26 p. U0l069b 24 ------- |