Process for Making Fish Fertilizer


Fish fertilizer, also known as fish emulsion, is a byproduct of the fishing industry. Leftover fish parts, like the head, guts, and bones, ended up in the trash can and eventually in the landfill. As the processed-fish-food market increased, so did the excess fish parts. All those excess fish parts used to be dumped back into the ocean or thrown into the garbage can. Now, they're turned into fish fertilizer.

Type of fish used

While small-scale fish-fertilizer processing plants use leftover fish parts, the larger processing plants use the menhaden fish species for creating fish fertilizer. Menhaden are approximately 8 inches long and live in the Atlantic and Caribbean oceans. This particular type of fish has no edible value for humans because it is bony, oily and has very little edible meat.


Once caught, the fish are shipped to the processing plant where they are loaded onto a conveyor belt that leads to an oven. The fish are cooked at 210 degrees Fahrenheit. They then go through a pressing machine where all of the oils and liquids are squeezed out of the fish. Once all the liquid is removed from the fish, they are sent into a chopper where they are chopped into pieces and then dumped into a large vat where they are boiled until thick and gummy.


Because fish and fish byproducts, like all living creatures, create gases when they start to decay, an additive is required to prevent the gases from forming. Phosphoric acid is added to the fish goo to prevent decay and remove the decaying fish smell from the end product.

Final Product

The final product is a fish emulsion, or fish fertilizer, that's ready to be bottled and shipped to distributors. Smaller processing plants usually bottle and ship their own products. However, the larger processing centers ship the fish solubles by rail car to manufacturers to be bottled and shipped. The rail cars of fish goo are sent to fish fertilizers, as well as pet food manufacturers to be used as a flavoring in dog and cat food.

Make Your Own at Home

If you own a fish tank with fish in it, then you have a weakened version of fish fertilizer, or emulsion, every time you change the water in the fish tank. Simply take the old water and dump it directly on your plants. Another way to make your own fish fertilizer is to take the fish parts, put them in a pan of water, and boil them for about one hour. Cut any large pieces into smaller pieces. Allow to cool and then pour around your plants.

Keywords: Fish fertilizer, Fish emulsion, Making fish fertilizer

About this Author

Katherine Bostick has been writing since 1993. She is a freelance writer and has written articles for both the 'Spectator' and the 'Crossties' newspapers. Bostick writes articles on educational topics, personal essays, health topics, current events, and more. Bostick performs copy editing and book review services as well as produces her own local newspaper in South Florida.