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.