To overcome the problem wherein the treatment cost is high because although a waste liquor is centrifuged to separate solids and fat and oil there from in waste liquor treatment in scallop entrail treatment equipment, the emulsified fat contained in the waste liquor can not be completely removed; the unremoved fat forms sludge adhering to the inside wall of a drier within a short time in a drying step and results in markedly lowered thermal conductiv ity and the consequent drop in the capacity of the drier to dry the whole waste liquor; and the surplus waste liquor is therefore obliged to be disposed of at a high cost by a dealer.

A waste liquor produced in the scallop entrail treatment is mixed in a certain ratio with a marine waste used as a soil conditioner or a fertilizer and prepared by grinding and drying matters adhering on shells and shells and then drying the ground product in a drier. The ratio of the marine waste to the waste liquor is at least 10:1 by weight.