Composting treatment and fertilizer properties of golden mussel (Limnoperna fortunei) mixed with dairy cow manure

The objective of this study was to examine the composting characteristics of a mixture of golden mussels collected in the Kanto region of Japan in 2019 and dairy cow manure in order to determine a treatment method for golden mussels after their extermination. To examine the characteristics of golden mussels, two experiments were carried out. (1) Nylon-bag experiment to clarify the specific degradability of golden mussels, and (2) Mixed composting experiment to clarify the properties of compost by mixing golden mussels and dairy cow manure at a predetermined ratio, using 10-L-volume fermenters. In the nylon-bag experiment, the organic matter degradation ratio of golden mussels reached 60% in the dairy cow manure compost. In the mixed composting experiment, the composting substrate based on dairy cow manure was mixed with golden mussels at the mixing ratio of 0%, 10%, 30%, and 50%. Our results showed that the organic matter decomposition rates ranged from 21.7 to 31.4%, indicating good progress of the composting process. The calcium concentration in the compost was higher with a higher mixing ratio of the golden mussel mixture. Moreover, the results of a 21-day plant harm test using the Japanese mustard spinach showed no harms due to the toxic substance, and the odor levels decreased below the environmental regulatory limits of 20 of odor index by composting and drying. Therefore, it was concluded that composting is one of the effective methods for the treatment of exterminated golden mussels. However, more experiments on the plant are necessary to investigate the sustainability of the proposed level on human health.