rather than chemicals. This process has been incorporated into certain resource recovery systems to recover paper fibers from municipal solid waste.

4.3.16.12 Source separation is usually preferred over separation of materials at the final disposal site because it is easier, less expensive, requires limited equipment, and generally results in a higher grade of recovered material. Disposal site separation does, however, yield concentrated recycle streams and shows reduced transportation costs over source separation/collection options.

4.3.16.13 Source Separation. DoD Directive 4165.60 (Dec 1986 Draft version) "Solid, Hazardous and Petroleum Waste Management" requires the recovery and recycling of solid and other waste materials to the maximum extent practicable. Source separation is one of the simplest methods of compliance with this requirement. Separation of other materials for which there is a market may be accomplished and is encouraged. A source separation program may be instituted at an installation only after the DRMO determines that markets exist for the separated materials. If markets do not exist, source separation is not required. The minimum requirements for source separation considerations

3. Corrugated containers (cardboard) installations where commercial establishments collectively generate more than 10 tons per month.

4.3.17 Recovery of Energy

4.3.17.1 General. Energy recovery is now becoming a very popular method for disposal of solid waste. The cost of disposal can vary substantially. An economic study must be done at each installation to determine if waste to energy is feasible. Sale of steam or electricity and tipping fees can provide income for large installations. This income must offset operating costs including maintenance. Maintenance costs are typically very high in large RDF units. For small incinerators (more typical at military installations), waste volume reduction is usually the primary goal. Here the cost of the incinerator (operating and depreciation) must be offset by savings in other waste disposal practices (e.g., landfill). (Some installations use incinerators to provide supplementary building heat especially in winter months.) At military installations, small incinerators are good candidates to supplement steam or hot water heating requirements. Generation of electricity usually requires large capacity furnaces such as those shown in Figures 4-3-17A and B to be economical. Few military installations are large enough to support an incinerator that produces primarily electricity. Table 4-3-17A lists processes for recovering energy from solid wastes either as thermal energy or stored chemical energy.

4.3.17.2 Energy recovery by incineration typically takes one of four different methods. The large-sized waterwall mass burning systems (Figure 4-3-17A) are generally preferred in smaller cities. The prepared fuels of RDF systems are favored where materials recovery is an important

Comment

Hydrolysis

local issue. The modular mass burning combustion units with waste heat recovery are also popular (Figure 4-3-17B). LaRoc (1988) provides a good description of technologies currently available in the U.S. Modular mass burning units are probably the best choice for military installations. They provide flexibility to meet the changing needs of a base.

4.3.17.3 Much design and operating experience on municipal solid waste (MSW) combustion has been gained in Japan and Western Europe over the past decade as the volume reduction of wastes has been stimulated by the declining availability and increasing cost of landfills (Brna 1988). Nearly 2000 MSW units in Japan and several hundred in Western Europe are now operating, with the trend now being waste-to-energy conversion rather than simply incineration to reduce volume. Technology developed in Japan and Western Europe has been beneficial to the U.S., where over 100 MSW combustion systems are now operational, and a similar number are in the construction or conceptual development phase.

4.3.17.4 The reduction of waste volume by combustion results in air pollution, including pollutants not currently regulated by the EPA. Pollutants/emissions and methods of control require analyses in Environmental Assessments. Table 4-3-17B shows the U.S. standards along with those of several states and countries (Brna and Sedman 1987). However, the EPA has announced its intention to further regulate emissions from MSW combustors and proposes promulgation of these regulations in December 1990. Currently, studies are under way to determine which pollutants to regulate and to what extent. As indicated in Table 4-3-17B, classes of pollutants currently regulated by one or more of the entities listed include: trace organics (dioxins, total organics), acid gases (HC1, S02), trace heavy metals (Hg, Cd, T1), and particulate matter. The listing in Table 4-3-17B is not intended to be complete. For example, West Germany regulates the emissions of more trace metals, and some U.S. states, as well as Japan and West Germany, have NOx requirements/guidelines.

4.3.17.5 Noting the classes of pollutants that are currently regulated and their potential for regulation in the U.S.--on a national, state, or local level--the air pollution control strategy selected for a given plant shall have the potential for multi-pollutant control, if costly retrofitting or upgrading is to be minimized in meeting future regulations. Residues, although small in volume relative to unburned wastes, contain concentrated pollutants requiring environmentally safe disposition.

4.3.17.6 Emission Control Technologies

4.3.17.7 Historically, emission control on incinerators has focused on particulate removal. Tables 4-3-17C and D (Tchobanoglous, Theisen, and Eliassen 1977) show several equipment types and rate their relative performance in removing particles.

4.3.17.8 Recent developments and perceived trends have switched the emphasis to removal of acid gases, trace organics, and trace heavy metals.

4.3.17.9 Wet or dry scrubbers are effective for controlling pollutants (acid gases, trace organics, trace heavy metals, and particulate

TABLE 4-3-17B

Selected Emissions Standards for Municipal Waste Incinerators (Brna and Sedman 1987)

(1) Revised pollution standards scheduled to be proposed in 1989.

(2) Swedish Environmental Protection Board's 'Temporary Emission Goals, July 1986.
(3) California regulations permit more stringent local limits. Two state guidelines are reported: 0.1 gr/dscf (25 mg/m3) for total solid
particulates (TSP) and 0.668 gr/dscf (26 ng/m3) for particles less than 2.

(4) Based on continuous gas flows > 25,288 scfm (40,000 3/h). For flows 25,288 scfa, the particulate matter standard is 0.20 gr/dscf
(500 mg/m3). For new plants in special areas, this standard is .033 gr/dscf (80 g/m3) for plants having > 25,286 scfm and 8.961 gr/dscf for
those having 25,280 scfn.

(5) Based on formula related to stack height and plant location. Typically, plant sulfur dioxide emissions range from 66 to 100 ppm so that control is not required except for new plants in special areas.

(6) Pollutant control requires use of the Best Available Control Technology (BACT), but no technology is specified.

(7) The use of dry gas scrubbers and baghouses is expected to improve removal over electrostatic precipitators alone.