Stabilization and utilization of seafood processing waste as a slow release nitrogenous fertilizer for production of cabbage in Florida, USA and mushroom in Ghana, Africa

Abstract

Seafood wastes were evaluated for the production of cabbage and mushrooms as a means of managing the vast amounts of organic waste currently being generated by fast growing seafood industry in Florida, USA and Ghana, Africa. Seafood wastes are presently being deposed of by burning, dumping in landfills or out into the sea, thereby creating an unsustainable environmental problem. Utilizing bio conversion technology such as the slow release nutrients for agriculturally based activities like producing mushroom will profitably reduce seafood waste while enhancing environmental quality. In this study, seafood wastes were stabilized with citric acid to produce mixtures of 3% and 5% and 10% concentrations. Molasses were also used as a waste treatment to generate a 5% concentration of the additive and intensity of waste odor was monitored over six weeks. Sawdust was separately mixed with fresh fish waste (FFW) and cooked fish waste (CFW), placed in heat resistant transparent polyethylene sachets and compared for their effectiveness to promote mushroom growth. Each sterile bag was then aseptically inoculated with three different varieties of oyster mushroom (Pleurotus species) which included Pleurotus eous, a hybrid of Pleurotus eous and Pleurotus aestreatus. The bags were then incubated for five weeks under ambient temperature and controlled humidity. Mycelia growth was determined at 3 day-intervals. The results indicated that the growth of oyster mushrooms was fastest with FFW when compared to CFW and the control P. eous and P. aestreatus exhibited uniformed spread of mycelia in the compost bags, oyster mushrooms produced bigger and firmer fruiting bodies compared to control substrates of rice brand (CRB). The fastest mycelia growth was obtained for P. eous which completely colonized FFW and CFW substrates within 26 days. The cabbage fertilization was based on the plant nitrogen requirement and nitrogen content of fish waste (organic) and commercial (inorganic) fertilizer used. The stabilized fish waste acidified the soil and generated plants with yields significantly lower (p<0.05) than the commercial treatment. Nitrogen release from the fish waste was mainly in the form of nitrate, which appeared to be rapid in the early stages of the plant growth and was almost exhausted at harvest time showing potentials of reducing nitrogen pollution of ground water. The implications of this study are that seafood waste could be used to cultivate a very nutritious food substance while at the same time promoting environmental sustainability