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INTEGRATING VESSEL AND SHORESIDE GARBAGE MANAGEMENT 150 fishermen using trawls or scallop or clam dredges. Other bags will deteriorate eventually and the contents will become part of the sedimentary record. Incinerators Incineration devices range from primitive "bum barrels" to complex dual- chamber systems with sophisticated emission controls. True incineration uses controlled combustion to achieve near-total destruction of waste with minimal emissions, so the more rudimentary bum barrels and older "fireboxes" seen on some ships are not representative of the technologies now available (Chang, 1990). The latest models have multiple chambers in order to maximize combustion of the waste and consume the resulting gases, and some of the exhaust heat can be reclaimed for other uses (Whitten and Wade, 1994). The IMO recently adopted standards for shipboard incinerators in order to document the technologies acceptable under Annex V and establish combustion performance standards in line with modem capabilities (the standards may be found at the end of Appendix B). The government of Bermuda also has established standards and licensed two ships to use incinerators (T. Sleeter, senior surveyor, Bermuda Ministry of the Environment, personal communication to Marine Board staff, June 2, 1994; Bermuda Ministry of the Environment, undated). Properly designed and operated incinerators can bum successfully most types of garbage, including paper, cardboard, and, under certain conditions, plastics (metal and glass cannot be burned). A number of acceptable, purpose- built marine designs are manufactured and sold for commercial use. Several units with tailor-made sorting and ash-handling systems are now in service (see Figure 5-1). These integrated systems have enabled passenger vessels to comply with Annex V in situations where compliance would have been unmanageable otherwise. Many recently constructed cruise ships have one or two high- capacity incinerators (Whitten and Wade, 1994), and some government vessels are equipped with incinerators as well. The National Oceanic and Atmospheric Administration, despite some poor experiences with units installed on its fleet, has been advised to equip its vessels with either trash compactors or appropriately designed incinerators (Art Anderson Associates, 1993). The Coast Guard has purchased and installed a prototype unit meeting IMO standards on one of its cutters (Sara Ju, Coast Guard, personal communication to Marine Board staff, August 18, 1994). It is important that the equipment selected be appropriate, that seafarers learn to use it proficiently, and that the units not be misused. Controlled combustion must be sustained in order to get good waste destruction; an incinerator is not appropriate for a vessel that generates very little or erratic amounts of waste. If fed too little waste, or surges of waste, an incinerator can perform poorly; either destruction may be inadequate or operating problems may arise within the unit. Thus, there are many instances where a vessel operator would do well to avoid relying on an incinerator. On the other hand, incinerators may be appropriate for
INTEGRATING VESSEL AND SHORESIDE GARBAGE MANAGEMENT Figure 5-1 Cruise ship waste management systems. Source: Princess Cruises. 151
INTEGRATING VESSEL AND SHORESIDE GARBAGE MANAGEMENT 152 use on ships with large populations or that generate waste streams sufficient to sustain uniform combustion. Vessels in this category include ships carrying more than 100 persons, large fish processing or factory ships, and research ships on long voyages. In the United States, there has been some public uncertainty about incineration of wastes due to concerns that emissions and residues resulting from use of this equipment cause more problems than they solve. Surveys by industry (an example is Kiser et al., 1994) suggest there is increasing public acceptance of and satisfaction with incineration as part of an integrated waste management strategy. The committee did not find any studies on this issue conducted independent of industry or groups opposed to incineration. While old incinerators could not meet current standards, the state of the art has progressed, and, in addition to the guidelines issued recently by IMO for on-board incinerators, stringent new operating standards have been established for units employed on land. The primary concerns are whether the stack emissions or the ash resulting from fuel combustion pose hazards. Because its focus was on solid waste, the committee did not examine the air emissions issue in depth, but it deserves attention. The IMO guidelines for Annex V implementation recognize the potential for air pollution and therefore discourage use of incinerators in ports in or near urban areas. The Coast Guard plans to conduct emissions tests on its prototype unit. There is some legitimate concern among American ship operators that future restrictions on air emissions (International Maritime Organization, 1994a) could make existing shipboard incinerators obsolete. An additional concern is that the performance of incinerator technology installed to enable Annex V compliance is difficult to monitor; however, reliable instrumentation and recording units are available that document whether emissions are within regulatory standards. The committee did examine the ash issue and found little cause for concern. Combustion of solid waste produces bottom ash (pieces of glass and metal, vitrified clays, and ''clinkers'') and fly ash (fine, lightweight particles). Tests conducted on the ash from a cruise ship incinerator showed that key contaminant levels not only were non-hazardous according to EPA standards but also were lower than those for ash produced by a municipal waste-to-energy plant (see Table 5-1).4 (The materials burned on the ship did not include plastics.) Thus, at least for this particular batch of materials burned in this specific incinerator, the ash did not appear to pose a hazard, whether discharged overboard or in a landfill. Incinerator ash, including clinkers, is considered operational waste under Annex 4 Shipboard incineration becomes even more attractive considering that it generates only one-third as much ash as is produced by a municipal waste-to-energy plant. The difference is due to the fighter weight of ship-generated garbage (e.g., light plastics, cardboard) as compared to shore-generated waste, which may include heavy materials such as wood and leather.
INTEGRATING VESSEL AND SHORESIDE GARBAGE MANAGEMENT 153 TABLE 5-1 Comparison of Contaminant Levels in Ash from a Municipal Waste-to- Energy (WTE) Plant and a Cruise Ship Incinerator (in milligrams per liter)a,b Chemical WTE Plant Ash Ship Ash Arsenic 0.093 not detected Cadmium 0.012 not detected Chromium 0.009 0.62 Copper 0.157 not measured Lead 0.121 not detected Mercury 0.0009 not detected a The ash tested was obtained from the Delaware County Resource Recovery Facility and the ship Fascination of the Princess Cruises fleet. b Tests were conducted using the EPA's Toxic Characteristics Leaching Procedure, which discriminates between non-hazardous ash (which can be landfilled with other solid waste) and ash classified as hazardous waste. In the leaching process, any metallic compounds in the ash are dissolved in water. V and therefore may be discharged at least 12 nautical miles from shore (except in special areas). However, the IMO implementation guidelines recommend holding on board the ash from combustion of some plastic products that may contain toxic residues.5 The committee's findings with respect to the ash are echoed by Bermudian research, which was motivated by that island's dwindling land space for garbage disposal. Those studies assessed the effects of dumping incinerator ash into landfills by focusing on the leachate expected to seep into the nearby marine environment. Results indicated no demonstrable increase in the concentration of metals in the water column (Knap et al., 1992; Hjelmar, 1993). The government has issued permits to two cruise ships for the use of incinerators while in Bermudian ports and while underway in their waters. Discharge of ash is not permitted within Bermuda's Exclusive Economic Zone. If conducted in accordance with the IMO standards, incineration offers an opportunity for ships generating large amounts of garbage to achieve self-con 5 The landing of incinerator ash in the United States could be affected by a recent U.S. Supreme Court ruling (92-1889, issued May 2, 1994) that all ash from municipal incinerators is assumed to be hazardous unless proven otherwise (Whitten and Wade, 1994).