Thurston Sets Out to Make His Own Fish Fertilizer

Published in 2015 by The St. Ignace News

Download PDF

“It really doesn’t smell at all, once it’s fermented,” Dave Thurston said, holding out a bottle of brown, opaque liquid. He’s right. It smells a little oily, with a tang of vinegar, more like a salad dressing than a fertilizer primarily composed of fish innards.

Mr. Thurston has loved growing things since he was a small boy helping his mother in the garden. He also loves experimenting with new things. When those two interests met at his 12-acre Moran hobby farm last summer, he set himself to the task of making his own, all-natural fertilizer.

“We raise rabbits, so we use rabbit manure, but we also have a lot of fish by-products in this area, so I decided to try and make something out of that,” he said.

He initially tried letting fish remains decompose on their own, but the stench became unbearable. The most common method for breaking fish down into a fertilizer that doesn’t smell involves cooking the fish parts, but that destroys the nutrients that make fish-based fertilizers so healthy for plants.

So he set out to make the less-common fish hydrolysate fertilizer.

To make the fertilizer, Mr. Thurston combines fish parts with water, milk, sugar, enzymes, and acids, then leaves the mixture to ferment in plastic barrels. Four to six weeks later, the liquid is strained and bottled. The process roughly resembles the same method used to make yogurt, and can only be completed during the summer when weather conditions are conducive to the process, Mr. Thurston said.

More than 1,000 pounds of fish parts from the nearby Mackinac Straits Fish Company went into Mr. Thurston’s first batch of fertilizer, resulting in 250 gallons. Of that, 70 gallons remain. The fertilizer is stored in containers donated for that purpose by friends. The three bottles on display in his Bertrand Street chiropractic office originally held juice.

Some of the fertilizer has been used on the Thurston family’s Moran property, where they grow garlic, raspberries, currants, gooseberries, grapes, herbs, apples, and mulberries. In addition to fertilizing the soil with the fish hydrosol, Mr. Thurston has sprayed some on the leaves of his berry bushes and fruit trees.

“We had an amazing crop of everything, especially given how cold last summer was,” Mr. Thurston said. “A lot of other people report back to me that they’re happy with it, too.”

The fertilizer’s impact on friends’ violets and geraniums has helped spread the word and Mr. Thurston has begun receiving orders by phone from people in St. Ignace, Moran, and Mackinac Island.

If the demand continues to increase, he hopes to increase production this year. Mr. Thurston is working with other area fish markets to secure the raw materials needed for the fertilizer, which he sells for $15 a gallon. It must be well diluted for use. Mr. Thurston is beginning his first batch of the summer this week and expects it to be completed in June.