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Tackling Marine Debris in the 21st Century
and slow thermal oxidation (Gregory and Andrady, 2003), which slowly physically break down the plastics. However, even in smaller pieces, the plastic remains a persistent pollution problem. Though placing the debris in a landfill can be a potentially inexpensive and technologically feasible method of management, because the DFG does not biodegrade, the material occupies landfill airspace indefinitely. In isolated places like Dutch Harbor, this can fill landfills relatively quickly, which creates disposal problems for DFG as well as other wastes.
The purpose of this appendix is to provide potential waste management options for fishing gear. Infrastructure related to waste management at ports and on ships has been previously addressed by the National Research Council (1995), which found that fishing vessels create the third largest quantity of waste (by mass) of the various categories of ships defined (behind recreational and day boats) with a generation rate of 1.85 kg per person per day. Recommendations from the National Research Council included a national infrastructure for the collection and management (recycling and disposal) of old DFG (National Research Council, 1995).
Various options for management of waste on ships are outlined by Hutto (2001); however, this appendix specifically focuses on management of waste fishing gear. After a brief discussion of the composition of fishing gear and waste management, various management and disposal technologies (other than landfilling) for fishing gear, particularly DFG, are described. Table E.1 summarizes these various options and compares them based on their current applicability, feasibility, and requirements.
COMPOSITION OF FISHING GEAR WASTE STREAM
There has been extensive collection and identification of DFG throughout the world (Dagli et al., 1990; Kiessling, 2003; Timmers et al., 2005). Fishing gear was historically composed of natural fibers; nets were composed of cotton flax and hemp (Timmers et al., 2005). When invented, synthetic fibers had many advantages over natural fibers, including durability. This durability also makes DFG persist in the environment. Various studies have been conducted on the composition of DFG—primarily nets. Gregory and Andrady (2003) note that synthetic yarns used in fishing gear include nylon 6, nylon 66, polyester, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, and polyvinyl acetate. Dagli et al. (1990) collected 1,000 kg of DFG to examine the gear for potential recycling of plastic. Of the 1,000 kg collected, 550 kg represented 49 separate items, including individual nets, individual lines, net combinations, and net/line combinations. The nets were composed of nylon 6, nylon 66, and high-density polyethylene (HDPE); lines were composed of mostly polypropylene. The study also found that nylons could be coated with