Abstract
Scallop entrails include a lot of nutrient such as nitrogen, phosphorus, and potassium, which contain toxic heavy metal such as cadmium in digestive gland. In this work, the current situation of scallop entrails recycling was investigated. Besides, hydrothermal treatment using subcritical water (HTSW) was examined as a recovery method of liquid fertilizer from scallop entrails. 59 wt% of scallop entrails was recycled by composting and 34 wt% of that was recycled by feedstuff manufacturing respectively. In composting facilities, scallop entrails have been commonly mixed with other input wastes to adjust cadmium concentration of compost under 5 mg/kg. Some facilities have proven to be suffered from lack of input waste to mix with scallop entrails in some case. On the other hand, at the HTSW of scallop entrails and digestive gland in the condition of 200oC, RT=20 min, and L/S ratio=10, the extraction of fertilizer components such as nitrogen, phosphorus, and potassium to liquid product was maximized whereas the release of cadmium tended to be suppressed. The concentrations of heavy metals were lower than maximum permissible concentration of Fertilizer Regulation Act. From these results, HTSW was considered as one of feasible recycling methods for scallop entrails with separating cadmium from product.
