Pollution Abatement and By-Product Recovery
in the Shellfish Industry
EDWIN LEE JOHNSON, Vice President
QUINTIN P. PENISTON, President
Food, Chemical and Research Laboratories, Inc.
Seattle, Washington
INTRODUCTION
The shellfish industry, herein limited to Crustacea species, is of considerable,
and rapidly increasing, importance in many world localities. Current domestic
landings and imports of shrimp alone in the United States amount to more than one
half billion pounds per year. Characteristically, all species possess an exo-skelton
which is not used for food purposes. The yield of edible meat generally amounts to
from 17 percent live weight for small shrimp to about 25 percent for larger crab
species. The remainder is waste and in many fisheries this is discharged into harbor
waters adjacent to the processing facilities.
Food, Chemical & Research Laboratories, Inc. has been active for the past five
years in development of processes for separation of shellfish wastes into marketable
commodities of greater value than crude shellfish meals. Much of this work has been
supported by the U. S. Bureau of Commercial Fisheries. It was previously reported at
the 24th Purdue Conference May 8, 1969. Work is being continued under the joint
sponsorship by the Environmental Protection Agency and the City of Kodiak,
Alaska, FWPCA Project 11060-FJQ.
PROCESS DESCRIPTION
The process as originally conceived involves total recovery of waste constituents to produce calcium chloride brines, protein and chitin as by-products. It
would consist of two counter-current extraction treatments. The first would employ
waste hydrochloric acid to decompose calcium carbonate and produce calcium
chloride brine. By suitable control of flow and recycling, brine concentrations of the
order of 20 percent can be attained.
The residue, consisting of protein and chitin, is extracted with dilute sodium
hydroxide solution to dissolve and remove all of the protein in the waste as a sodium
proteinate solution. This extraction would also be conducted as a counter-current
operation in order to obtain high protein concentration in the extract.
Protein is recovered from the extracts by neutralization with hydrochloric acid
to the iso-electric point of the protein which occurs at a pH level of about 4.0. The
precipitated protein is separated from the supernate by filtration or centrifugation,
washed to reduce the salt content and dried.
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