Fish emulsion fertilizer is made several different ways depending on who is making it. The important thing to know is that fish emulsion goes through two stages of processing. The first stage breaks down the fish parts using enzymes, proteases, or chemicals. Then, and this is the important part, heat is used to break it down further and allow oils and other things like amino acids to be more easily removed. It’s this second stage of processing that makes fish emulsion less advantageous than fish hydrolysate. Fish emulsion fertilizer lacks many oils and proteins that fish hydrolysate fertilizer has in abundance.
Fish emulsion, a popular product used in organic agriculture, is used as a soluble fish fertilizer but is processed with heat. Enzymatically digested hydrolyzed fish retains more of the proteins, enzymes, vitamins and micronutrients than emulsions, which can be processed with high heat and acids. Heat tends to denature amino acids in proteins, making them unavailable to the plants. Enzymatic digestion of fish allows the minerals and amino acids to become readily available to plants and makes those nutrients water soluble, so you can use them in foliar spraying or through drip and other irrigation systems.