Decomposition of Waste Shells Using Multi-Complex Microorganisms

Abstract

Objectives : Korea is a global aquatic product producer/consumer country, and shellfish including oysters are no exception. Oysters occupy the largest proportion as a single variety in the domestic aquaculture industry. The production volume reaches an average of more than 300,000 tons per year. The oyster shells left after harvesting oyster is reaching over 280,000 tons/yr. About 70 % of these are recycled, but the remaining shells which are over 60,000 tons, causing serious environmental problems such as odor and water pollution. In order to solve this problem, some local governments investigated the possibility of applying microorganisms, but it was effective only to remove odors and it was not possible to decompose the oyster shell itself. In this study, an attempt was made to solve the problem of waste shell decomposition by using multi-complex microorganisms rather than microorganisms composed of a few species.Methods : As a waste food extinction facility in Korea, the first certified Q mark equipment was used. After mixing oyster shells and food wastes in a 1:1 ratio, they were subjected to decomposition and extinction treatment at a high temperature of 80 ℃ using multi-complex microorganisms. Multi-complex microorganisms are composed of various soil microorganisms, including aerobic and anaerobic microorganisms. They are in an activated ecosystem by forming a symbiotic relationship to obtain a strong decomposition synergistic effect.Results and Discussion : The composition of complex microorganisms was mainly Firmicutes at the beginning, but Proteobacteria accounted for a half after 29 hours from the start of the experiment, and after 77 hours, it was shifted to Firmicutes A. All-organic components were decomposed within 72 hours, and the shell was changed to a powder form, and the total weight was reduced to less than 10% of the input total weight. It was found that treatment for at least 48 hours was required to decompose organic components from food waste, and after the organic components were decomposed, oyster shells were transformed into fine particles. The main components of the particles were calcium carbonate, which was identified as Aragonite and Calcite.Conclusions : Considering that the main component of the shell is calcium carbonate, and the temperature at which calcium carbonate is decomposed into quicklime and carbon dioxide is around 800 ℃, the result of weight loss of the shell is difficult to explain with the existing thermal decomposition mechanism. It is necessary to explore further a new possible mechanism of shell decomposition by complex microorganisms.