Last year I made 40 gallons of fish fertilizer I expect kelp could be made the same. I used a lactic fermentation process which decomposed all the soft parts of the fish leaving behind bones and some larger scales.
I scaled up some instructions found on youtube videos which were mostly 5 gallons or less.
Equipment was a 60 gallon plastic Greek Olive drum with threaded and sealed lid.
For fermentation you need to exclude air entry. I fabricated an airlock using a 3/8" plastic tube from the top of the drum lead into a 1 gallon can 1/2 filled with water. This allows carbon dioxide generated in the fermenter to escape but air to remain excluded.
Lactic acid bacteria can be found wild in the air, I developed a culture by washing 2 pounds of white rice with 1 quart of water and placing the water in a bowl in a dark closet for a few days. Three days later the wash water had a sour fermented smell.
I added the fermentation to 5 gallons of whole milk in a 5 gallon bucket. Within 2 days the milk had curdled, with curds floating on top and whey underneath. Using a slotted spoon I removed the curds, about 1 gallon, and stored the whey in the refrigerator.
The curds were proteins and fat from the milk, the whey contained a large culture of active lactobacillus. The reason you incubate in milk is that the bacteria can feed on the lactose sugars in the milk and hopefully overwhelm and exclude other bacteria, molds, and yeasts.
Theoretically, this is the same process used for making cheese, except that most cheese makers use bought cultures and take more care in sterilization. Because I felt adventuresome, I did harvest the curds, pressed them and obtained what looked like a soft farmer's cheese. I did eat it for a few days, each day eating more until I detected some intestinal distress and decided to stop.
Everybody called it "Fish Cheese" and thought I was crazy for eating it and had a good laugh.
Meanwhile, I stored the lactobacillus whey 'serum' in 1 gallon milk jugs in the refrigerator. For the next 2 weeks each day I went to the fish market where I had pre-arranged to trade my windfall mangoes for fish guts, heads, spines, fins, shrimp peels, whatever scraps they ordinarily through into the bay. I also bought 100 pounds or so of ordinary white sugar. You can use any sugar or even molasses. Day by day as I got fish guts I put them into the drum, added some serum, covered everything with sugar and stirred. After a couple of weeks I had the drum full, had used up all the whey serum and had a fairly thick blend of fish parts floating inside and bubbling/fermenting.
Within a week the smell became fishy, sweet and sour smelling but definitely not the 'smell of rotten death' you might expect.
Quite a few people who looked in were surprised. It is probably something you wouldn't do in a small urban backyard but 50 feet away you didn't know anything except when opened stirring.
It took 2-3 months for fermentation to eventually slow down. I stirred it every week or so with a big stick. I understand that the bacteria produce lactic acid as their waste (like soured yogurt) which eventually ends their reproduction. The result was a thick gray slurry topped by fish oil and the bones and scales sunk to the bottom.
I wanted to try using the product in a sprayer, a mist blower, and through a fertigation system so I tried several ways of filtering it.
I also used a powerful drill and paint stirring attachment to try and blend/chop up stray bits in the drum.
That was difficult because all the strainers kept clogging up. The best product ended up being strained through a nylon mesh paint strainer and was fine enough to use in the equipment with only a few clogs. To get it through the strainer I had to manually squeeze it with my hands so I smelled like fish for a day or so.
The process could probably be improved if I fabricated some baskets of different mesh wire and just let it drip through over several days, but my location wasn't protected from varmints and I expected they might tear everything up at night. If I had access to running water and electricity I believe a used kitchen garbage disposal might help mince or grind the fish including the bones, but would work best if you had all the fish at one time not day-by day & little-by-little. The liquified product might also be decomposed faster and be strained easier. I also found that green papaya contains a flesh decomposing enzyme called papain which might speed up the process but might need to be added before fermentation. The remaining bones and scales at the bottom went into compost, and the last of the fish emulsion I soaked into 300 gallons of biochar I made last spring.
One interesting observation. I tossed a few mangoes into the fermenter when it was mainly full. When the fermenter was finished bubbling, the mangoes remained green and whole as if they had been preserved instead of decomposed.
No, I didn't try to eat that.
For the future I may just strain a few gallons for special foliar feeding purposes and use the rest as a drench.
I hope this description helps. I think the kelp would be decomposed in the same way but agree you'd need to rinse the salt.
I have a second drum and plan to double production this year.
Topic: How to make my own fish and kelp fertilizer? (Read 1992 times)