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Treasure Trove of Fertility: Composting Mussels

By Maria Dimengo

For about the last two years, I have been experimenting with composting mussels. Head to southern West Virginia and you’ll meet farmers who are learning to amend the brown, yellowish sandy soil deep within the Appalachian Plateau. The Berks-Pineville and Gilpin-Lily soil created by weathered shale, siltstone and sandstone can be unpredictable. Though it appears to be well drained in some areas and easily cultivated in others, the black gold they need to amend their crops is all but gone.

Here in the southern coalfields that surround Mullens, Itmann and Pineville, mountaintop soil and dirt can be tightly packed and tough to work.

Compost can take a long time to break down, especially when there are long stretches of dry hot weather.

I knew little about the soil in Mullens when I first started experimenting with my zebra mussel shell compost mix. I first made a visit there last summer and stumbled upon a row of gardens at the Mullens Opportunity Center while I was in town for a meeting.

There, I met the executive director of the Rural Appalachian Improvement League and a farm-to-school AmeriCorps worker who was caring for their summer crops and high-tunnel complex. I asked if I could return to Mullens with just the right remedy for their soil.

The author has experimented with a compost mix of zebra and quagga mussels.

Experimenting in Cleveland

I have been working with a compost mix of zebra and quagga mussels, invasive bivalves that are plentiful in and around the Great Lakes. Whenever I shared buckets of it with other farmers, we were excited to see the results. Few people care to understand the value of the mussels and instead, fear them, because of the way they wreak havoc on lakes, streams and inland waterways.

They are a nuisance because they can alter the entire ecosystem of a body of water if a tiny, single veliger travels on the hull of a boat and creates their own colonies. Luckily, the mussels I use in my compost are already dead, and far from the Guyandotte River that snakes alongside Mullens and other southern coal communities.

Plus, I only use the composted shells — not the actual mollusks — which grow like crazy in water temperatures of around 50-55 degrees and warmer.

The author’s compost is being used at school and community gardens.

I consider myself a casual scientist because I don’t hold a degree in botany, biology or earth science, but I do like to study conservation and focus on environmental issues that are beyond manageable for the governments and researchers who study them.

After I discovered mounds and mounds of the shells on Lake Erie, I found an online recipe for zebra mussel shell compost on the Cornell University website.

I took Cornell’s recipe, removed the peat and tinkered with the recipe so I could teach children to apply the compost in urban gardens. The goal was to teach them about turning lemons into lemonade, so they in turn could teach senior groups and refugees in the city who were looking for opportunities to amend their own backyard gardens.

The principal from Near West Intergenerational School, a charter school on the west side of Cleveland, found the idea in perfect alignment with their mission to think outside the box. She allowed me to work with a group of sixth and seventh graders, and after two years, they saw the benefits of using this compost firsthand. I asked them to write a letter to farmers about the compost as one of their assignments. One student wrote: “I would recommend that a farmer use zebra mussels, shells, chicken poo and sawdust because it works well for vegetables. In science class, we had a taste test for peppers. They were super good.”

Aliza, another student at the school, echoed what others in the class had to say. “Keep using the zebra compost for your crops,” she wrote. “The outcomes we saw in the peppers that were grown in the zebra compost was that the peppers grew very big.”

Real Results

When you first mix the recipe, your compost will look like the color of oatmeal cookie dough. But in two years, that same compost will create a moist black soil that makes a wonderful amendment.

In Cleveland, educators around town were asking me where they could harvest the shells to create their own mix, and some urban gardeners were feeding the shells to their chickens as a low-cost grit alternative.

Others were adding the uncomposted shells straight to hay, grass and other compostables and finding the end product great for container gardens.

We conducted a lot of informal trials at Kentucky Garden, which is a community farm across from the school. A fellow gardener suggested a great way to determine if my first batch was usable. “Maybe you could take four or five plants and put regular soil around them, like this,” he said. “Then, get an equal number of plants, add the zebra mussel compost and do the same thing … measure the height of each plant, then see how they grow.”

I knew it wouldn’t be an exact science, since my peppers would be taking up space in a community plot.

I simply couldn’t watch their progress every day, so I cordoned off a small section and placed each pepper in the ground. A handful of peppers received two cups of vegetable compost while the others received the zebra mussel shell mix. Each time I watered them, I was careful to give each plant the same amount. Twice, I amended the soil, giving each plant equal parts of compost.

Tomatoes growing in soil treated with mussel compost mix.

I couldn’t control what others did while I wasn’t around, but over time, I observed some interesting outcomes.

Each time I stopped by to water, the plants with the shells yielded peppers that were longer, stronger and wider.

In addition, plants with the shells had multiple yields, so I was constantly picking fresh peppers from my zebra plants.

It seemed whenever I would visit the plot to check on them, the plants with the shells were just bursting to be picked. The other plants lagged behind and took forever to grow. I gave my mix to other gardeners and they recorded similar results. One gardener said the flowers in his garden yielded brighter colors after using the zebra mussel shell compost.

What’s in the Shells?

Using shells to boost soil fertility is nothing new — eggshells are a given, and many farmers use oyster shells and fish waste to give their crops an extra boost. When I was doing research, I ran across a company called Coast of Maine Organic Products in Portland. The company’s Quoddy Blend contains lobster shells, which are said to be rich in nitrogen and chitin.

Cornell University’s Waste Management Institute Department of Crop and Soil Sciences experimented with the compost after receiving an EPA grant to compost zebra mussel shells at a New York waste facility.

They were one of the few resources I found online when I went looking for ways to re-purpose the shells into something useful. I wondered if anyone else had seen the value of using them for clean fill or other things, so I traveled to Ithaca to meet the researchers for myself.

At first they seemed surprised that I was reviving a recipe that was written so long ago, but they suggested that I cook my compost at least nine months to break down the pathogens.

They also suggested I build a two-can bioreactor to aerate the compost if I wanted to produce small-scale batches indoors.

They told me that the calcium carbonate in the shells is what gives plants a boost. When mixed with chicken poop and sawdust, zebra mussel shell compost can support an optimal pH level, especially when you compost the shells for two years or more.

Since I knew I would be working with young kids, I wanted to find out if zebra mussel compost is harmful.

I reached out to Remegio Confesor, a research scientist at Heidelberg University in Tiffin, Ohio. Confesor suggested I first test the shells for contamination and then test the compost to see if any toxins were being transferred to my soil. He said that anyone who performs compost analysis could help, since they look for heavy metals, lead, PCBs and other toxins.

Confesor and other researchers have been studying the nitrogen and phosphorus movement across Lake Erie waters because of recent algal blooms. With zebra and quagga mussels, there is a connection. Around 2002, a researcher by the name of Hank Vanderploeg looked at how zebra mussels selectively filter the phytoplankton that provide food to aquatic creatures. Apparently, zebra mussels will eat whatever they can filter, except for Microcystis, a species of freshwater cyanobacteria that create harmful algal blooms or HABs.

Once they’ve had their fill, zebra mussels excrete all the phosphate and ammonia nutrients so their excrement works like fertilizer, allowing the toxic algae to proliferate.

Researchers with the Great Lakes Environmental Research Laboratory (GLERL) also experimented with zebra mussels. Using special video equipment, they found that the mussels eat algae and filter the water, but spit Microcystis back into the water. During their selective feeding process, the mussels excrete nutrients like phosphate and ammonia, which serve to fertilize further growth of the harmful cyanobacteria.

So if we know that zebra mussels play a role in nutrient loading when they are alive, who’s to say they aren’t a valuable source when they’re dead? Whatever the outcome, we have moved our experiments to an Appalachian coal town, and now we have a whole new round of baselines and healthy crops to grow. I also hope to look at Japanese Knotweed and kudzu — two other invasives in Appalachia that have impacted the mountain valleys and riversides.

Recipe for Composting Mussels

Cornell researchers wanted to see if they could make a recipe for folks who might want to compost anywhere from 100 to 1,000 pounds of zebra mussels. Since a zebra mussel is mostly shell and hardly any organic matter, you probably need to mix mussels with some other organic material to provide the right nutrients for compost microorganisms.

After a number of small tests, the researchers found that a co-composting mixture of 1:14:17:18 parts by weight of peat, sawdust, poultry litter and water could be made and then mixed 1:1 with zebra mussels for composting.

An equal volume of wood chips for bulking was then added. Two compost piles were built, each containing one cubic yard of zebra mussels supplied by Rochester Gas and Electric on a bed of wood chips and perforated PVC drainage pipes. In monitoring the compost, it was observed that the shells probably help maintain good pore structure for airflow.

After three months of composting and maturing, the wood chips were screened out, the compost was mixed with various ratios of topsoil, and tomatoes and radishes were grown in the mixtures. All seedlings did as well or better than the topsoil alone.

Recipe Source: Erin McDonnell.

By Maria Dimengo. This article appeared in the December 2015 issue of Acres U.S.A.