A Novel Two-Phase Composting Process Using Shrimp Shells as an Amendment to Partly Composted Biomass

Abstract

Shrimp and crab shells as well as other seafood industry residues contain chitin as a major component. Partly degraded (oligomeric) chitin is recognized as an elicitor of plant defense mechanisms and a growth suppressor of pathogenic fungi. A method of composting shrimp shells was developed with the objective of obtaining a compost of good quality and characterized by a significant content of oligomeric chitin. The method consists in mixing peat moss, sawdust and a nitrogen rich biomass such as cow manure and composting them until the thermophilic phase is terminated. The immature compost is then amended with 30 percent of shrimp waste on a dry weight basis, inducing a second thermophilic phase. An enzymatic method was developed to monitor the process of chitin degradation and to determine the most appropriate moment to stop the composting process. It was also shown that the peak value of oligomeric chitin content is accompanied by a decisive drop in ammonium content. The shrimp waste-based composts produced by this novel two-phase method have significantly high levels of disease suppressive chitin derivatives than commercially available composts.