3.3 Relative Economics of the Systems

3.4 Resource Marketability and Its Effect on Economic Rankings 3.5 Municipal Vs Private Ownership.

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3.6 Resource Supply Contrasted with Plant Economics of Scale.

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SUMMARY

This survey and analysis of the present status of technology for resource recovery from mixed municipal waste shows that the national goal expressed in the Resource Recovery Act of 1970 has been perceived by the government and industry as one worthy of substantial commitment. A significant response has already been seen in the form of the development of numerous resource recovery processes. On the other hand, the development has been largely unfocused and uneven because the specific technological needs of resource recovery are not yet well defined. We appear, at this point, to have a rather impressive shopping list of technology to choose from, but do not know which system concepts to buy or even whether to buy at all. Part of the problem is that technological development has been focused on processing a "new" raw material stream--mixed municipal waste--but the resulting product output does not necessarily result in something for which there is a ready market.

Technical Summary: Only two methods are currently fully developed and practiced for the recovery of resources from mixed municipal waste-heat recovery from incinerators and composting. Heat recovery from incinerators has been practiced in Europe and Japan for some time. Recently, heat recovery incinerators of European design have been introduced into the U.S. and Canada. Although heat recovery from incinerators has been practiced for some time, there are still some significant technical problems with these systems such as erosion and corrosion of the boilers and reliable deliverability of the product. The technology of composting is well established. There are several composting techniques, the most successful being the Fairfield-Hardy and the Varro systems. Poor marketability of the finished product has been a factor in a rather unimpressive history of composting in the U.S.A.

There has been a marked increase in the development of new technology for resource recovery from municipal waste during the last few years. Included in this emerging technology are: (1) energy recovery processes, (2) materials recovery processes, (3) pyrolysis processes, and (4) chemical conversion processes.

The emerging energy recovery technology includes fuel recovery processes, steam generation processes, and electrical power generation processes. Energy recovery is applicable only to the organic fraction of wastes, but many of the energy recovery processes also recover some of the inorganics (metals and glass). Two of the promising fuel recovery systems are the Horner-Shifrin and the A. M. Kinney processes. The Horner-Shifrin process involves dry shredding of the refuse and using it as a supplementary

fuel in existing power plant furnaces.

A. M. Kinney has a design to wet pulp waste organics for use as a supplementary industrial or power plant fuel.

Two new steam generation systems, designed by the American Thermogen Company and Torrax Systems, Inc., involve the recovery of heat from the combustion of refuse in special furnaces. The novel aspect of these systems is the use of high-temperature furnaces which require no preseparation or preparation of the waste, and which melts all of the residue to a lava-like frit.

Another new energy recovery system, called the CPU-400, is designed to burn shredded municipal waste in a high pressure fluid-bed combuster and uses the hot gases to drive a gas turbine-electric generator. This system is presently in the pilot plant development stage.

The materials recovery processes are designed to remove paper, ferrous and nonferrous metals, and glass from the refuse. In most processes all four materials are recovered. Both wet and dry processes have been devised to separate the paper from mixed waste. Techniques to remove the metals both from the mixed waste and from incinerator residues are being developed. Most of the ferrous metal separation techniques are based upon magnetic separation--a well-developed technology. The glass is separated by air classifiers (separation by density) and color sorting using optical devices or by flotation techniques. The materials recovered in these systems are generally of a quality that subsequent refinement or additional upgrading may be necessary to obtain fully marketable products. The most developed materials recovery systems are the Black-Clawson Fibreclaim system, and an incinerator residue recovery system developed by the U.S. Bureau of Mines.

A number of organizations are in the process of developing pyrolysis processes that recover synthetic fuel oil, gas or other potentially valuable materials from municipal wastes. These pyrolysis systems involve the thermal degradation of the waste in a controlled amount of oxygen. Some of the products that have been obtained from municipal waste by pyrolysis systems are oils, gas, tar, acetone, and char. Pyrolysis is an attractive method for waste resource recovery because of the basic flexibility of the technique; changes in operating conditions can be made to vary the nature of the recovered products.

The Garrett Research and Development Company has developed a pyrolysis process that recovers synthetic fuel oil from refuse (glass and ferrous metal are also recovered). The Garrett system appears attractive because of the reported high yield of low sulfur oil and substitutability

for low-grade fuel oil. However, it has not yet been determined whether the recovered oil will be readily usable as a substitute for commercial fuel oils. Union Carbide has a high-temperature pyrolysis process from which the combustible off-gases can be cleaned for use as a fuel gas for utility furnaces. The adaptability of the synthetic gas to commercial furnace fuel systems has not been fully determined yet. Monsanto has a pyrolysis system that has been tested to a much greater extent than any of the other pyrolysis systems. Furthermore, their pyrolysis unit is based upon extensive rotary kiln design experience. Both facets speak well for probable success of the Monsanto pyrolysis system. The primary pyrolysis unit (fluid-bed type) proposed by the Hercules Company is feasible, but unproven; their back-up unit is a well-developed furnace for producing wood charcoal. Battelle Northwest and West Virginia University have also been working on the development of pyrolysis processes for mixed municipal wastes.

There are a variety of chemical conversion processes (anaerobic digestion, acid hydrolysis, wet oxidation, hydrogennation, and photodegradation) which have been conceived for mixed municipal waste, resulting in such products as proteins, methane, glucose sugar, oils, alcohol, yeasts, and other organic chemicals. Since most of these processes utilize only the cellulose portion of the waste, separation and pretreatment of the waste is necessary. Most of these processes are in early stages of development.

Economic Summary: The most obvious finding of our economic analysis is that resource recovery systems are not self-sustaining economic operations under the conditions of the analysis used. They do not recover revenue sufficient to offset total costs; all systems analyzed show a net cost of operation. However, where incineration, remote landfill, or other high-cost waste disposal is necessary, resource recovery offers an economically viable alternative. Most resource recovery systems show lower costs than conventional incineration (without resource recovery); several have net costs (for large capacity plants) low enough to compete with landfill, if the recovered products can be sold at or above the assumed prices.

Under the conditions used in the generalized economic analysis, the process ranking by lowest net cost is: (1) fuel recovery, (2) materials recovery, (3) pyrolysis, (4) composting, (5) steam generation with incinerator residue recovery, (6) steam recovery, (7) incinerator residue recovery, and (8) electrical energy generation. The net operational costs (based on a 1,000 TPD plant) range from about $3.00/ton for fuel recovery systems to about $9.00/ ton for electrical energy generation.

Most of the emerging systems for resource recovery utilize new technology or at least unique combinations of existing industrial technology. Political jurisdictional units are often hesitant to experiment with new or unproven technology since this represents a radical departure from traditional waste management practices and introduces "high risk" of taxpayer funds. This is true even though a system developer may guarantee performance of a specific system. However, in order to introduce technically and economically viable disposal/resource, recovery systems waste management jurisdictions will be required to adopt relatively sophisticated technology and competitive marketing skills.

Most of the resource recovery systems examined are capital intensive, i.e., a large capital investment is required for each system. Therefore, the fixed costs of operation are quite high in relation to total costs. These systems should be operated at or near capacity to minimize unit costs and maximize salable product output. In addition, the systems show economies of scale, so that the larger the system, the more attractive the unit cost of operation.

Perhaps the most critical economic factor is marketability of the output products All of the resource recovery techniques produce products that must compete with established commodities directly or indirectly in the marketplace. The variables of most importance are: unit price (or value), throughput quantity and the percent of input (or output) that is salable. In turn, these variables are dependent upon the quality of the recovered product and its applications or demand in the specific situation in which it occurs.

In summary, waste processing for resource recovery requires sophisticated industrial technology and a large capital investment, and must be operated within competitive industrial market conditions. Nonetheless, resource recovery is a viable alternative to traditional waste disposal practices and should be carefully assessed by any municipality or jurisdictional unit faced with a waste disposal investment decision and/or highcost waste disposal.

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