What fish and parts of the fish are used for making fish fertilizer? By-products or waste materials from various types of fish are used. And although technically several varieties of fish can be used, mostly Menhaden fish that contain few amounts of meat and used for making animal feed are used.

The first step is to cook the fish and to squeeze its juice and oils by pressing. The oil is removed while the leftover solids can be ground and baked into protein meals and fed to animals. The juice of the fish is brought to a boil until it becomes more concentrated and results in a fish emulsion.

To hinder fermentation and extend its shelf-life, phosphoric acid is added to the emulsion. The percentage of phosphoric acid in the solution should be under 1% to meet the USDA criteria for organic products.

Although formulations vary, fish emulsion liquid fertilizer typically contains approximately four to five percent nitrogen (N), two percent phosphorus (P), two percent potassium (K), and trace elements. Trace elements, also called micronutrients, are chemical elements that plants need in minute quantities in order to thrive.