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Fish-Waste Composting
There's nothing worse than a pile of dead fish. Except maybe a pile of the leftover parts of dead fish - heads, tails, internal organs and all that. Disposing of this waste is a problem for anyone who cleans and processes fish, from big commercial food processors to small sport-fishing operations.
A promising solution, according to a Cornell professor, is composting, just like the process home gardeners use to make their own soil enhancer. "Large-scale industrial composting is more difficult, but it still may be the simplest and cheapest waste-stabilizing technology available to the processor," says Joe Regenstein, a Cornell professor of food science who teaches courses in food waste management and food law.
Fish-waste composting is a little trickier than the backyard variety, Regenstein admits. So he and Susan Goldhor, director of the Center for Applied Regional Studies, a New England environmental organization, are producing an instructional videotape explaining the technique, based in large part on their research in developing and demonstrating simple small systems. The project is sponsored by the National Fisheries Institute, which will distribute the tape to fish processors nationwide.
"The tape is for everybody who handles fish, " Regenstein says. "It will show how to actually construct a composting pile on different scales, for the medium-sized producer or small producer." That means all the way down to a "garbage-can-sized" operation that could be used by a small fish farmer, he explains. Regenstein, who is vice-chairman of the Cornell Aquaculture Program, has been researching small-scale composting methods with funding from the National Sea Grant Institute.
In composting, garbage such as fish parts is mixed with plant waste such as sawdust, peat, wood chips, leaves, branches or bark. Microorganisms in the pile feed on the waste and over a period of several months convert it into a rich humus. In the process, the microorganisms generate a great deal of heat which pasteurizes the product, eliminating odor and destroying weed seeds and disease organisms.
The resultant product usually is sold as soil amendment or soil enhancer, Goldhor says. "Composting is no more difficult than brewing beer or baking bread, two other processes that take advantage of a different kind of microorganism," she adds. "Anyone can do it, but as with brewing or baking, no one should expect a perfect process or a saleable product the first time around."
Until recently it was common practice to dump fish waste back into the lake or ocean. The trouble was, dumping it all in one place could overload the ecosystem, so such dumping has been banned. That left New England fish processing plants, for example, with a quarter million pounds of waste a week on their hands. Some have found other markets, grinding up the waste to make cat food or converting it to liquid fertilizer by a process called hydrolysis, but much of it is still going into landfills. There are, so far, only two or three large-scale fish composting operations, Regenstein says.
Many small processors have started to use composting, however. For example, some small sport-fishing operations on Lake Ontario are using technology demonstrated by Regenstein and Goldhor in conjunction with the New York Sea Grant Institute Marine Advisory Service to compost the waste from fish cleaned by their customers in lakeside piles. When the customers come back a year later they can take the composted product home to fertilize their gardens.
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