Bob Van Veldhuizen and Mingchu Zhang test temperatures in a compost pile in Homer, Alaska.
Thinking about the waste left over after 2 million metric tons of fish are filleted in Alaska each year is almost painful for Dr. Mingchu Zhang.
Rather than stew about the problem, Zhang, associate professor of agronomy and soil sciences at SNRAS, cooked up a solution. Through research and testing he and his associates created a recipe for fish compost that can be used to enrich the soil and improve agricultural yield while at the same time making use of a byproduct that would ordinarily be discarded in the state’s seas or rivers.
“Using fish waste in the soil works,” Zhang said, due to the nutrient content. Nitrogen, phosphorus, potash, zinc, and copper, found in fish waste, are essential nutrients for plant growth.
While the fishing industry routinely grinds up its waste and returns it to the local water source, waste for compost doesn’t need to be processed at all. Heads, tails, and other fish parts are mixed with peat moss and allowed to heat up in the summer sun, creating an organic, inexpensive solution for gardeners. The fishermen in Homer were so supportive of the tests and pleased that they didn’t have to grind up and dispose of the waste that they even made regular deliveries of their byproducts to the farm.
With the summer warmth heating the compost piles, it took only two months to complete the process. Probes measuring the internal temperatures showed that at times the mixture was as hot as 120˚F. The only maintenance throughout the composting process is occasional turning of the mixture and sometimes adding moisture.
Working with a Homer farm called Ocean Earth in June and July of 2008, Zhang conducted field trials that demonstrated the nutritional value of the compost. Plots were tested at different ratios of compost to soil and resulting salt concentrations were measured. One of the most visible signs that the compost is useful is a photograph Zhang took of a hay field where half the crop had no compost applied and the other had a generous portion. The side with the compost turned out lush and green, while the other appeared pale and sickly.
Bob Pawlowski, director of the Alaska Fisheries Development Foundation, has been a supporter of Zhang’s research because “it’s very important we do everything we can to use seafood processing waste versus just dumping it.”
Calling this “a good environmental project,” Pawlowski said he envisions the fertilizer being useful in all areas of the state. Rural places can create community gardens and grow their own produce. In urban areas he pictures school lawns and golf courses perking up when the mixture is applied.
“The obstacles are minimal,” Pawlowski said. “On one acre you can mix 100,000 pounds of salmon waste with 400,000 pounds of peat. The yield is one million pounds of garden soil.”
He believes that down the road there could be a market for selling the product to customers in California and Arizona who would appreciate the water retention properties the compost has.
“It’s an excellent university project,” Pawlowski said. “It will be applicable throughout Alaska wherever there are peat bogs.”
Most often, regions that are tied to the fishing industry also have rich reserves of peat moss. This makes for a low-cost way to transition the waste into a valuable product. In addition to the Homer testing, experiments are being conducted in Fairbanks and Palmer. At the Matanuska Experiment Farm, Zhang’s doctoral student Jodie Anderson is using plastic containers as “cookers” to try new ways of creating fish compost. In addition to working peat moss into the fish waste, she is experimenting with cardboard and hay. “We are working toward concrete solutions,” Zhang said.
He is creating a users’ manual so farmers will know how to produce the product to an optimum blend and apply it properly. A proposal to the USDA to get fishing communities involved in the project is also in the works.
A composting workshop was taught in Dillingham in April and Zhang plans to teach a course in Fairbanks in the near future.
When making presentations about the compost project, Zhang likes to quote a poem by Ryan Bundy he found on a plaque near the shoreline in Homer.
The sea tells a story
It tells of the cycle of life
Running through the waters
Fish, spawning, dying, sinking to the ocean
Returning to the circle that engulfs life.
“That says what we do,” Zhang said.
Publications, related information, and links on composting and fisheries in Alaska:
• Indian Country Extension, Tanana Chiefs’ Conference. Webpage and links on rural agriculture and traditional knowledge in Alaska.
•Composting tips provided by UAF Cooperative Extension Service.
*Alaska Fish Byproducts Information from the State of Alaska Office of Fisheries Development
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