Adding Value to Brown Crab (Cancer pagurus) Shell Waste

The European shellfish industry is a major source of biowaste. The processing of crustaceans in the EU alone is estimated to result in more than 750,000 tonnes per year of shell waste. It costs one shellfish processor, generating between 420 and 480 tonnes per year of crab shell waste, over €20,000 per year to have the waste rendered into fish meal by another company. A knowledge transfer project aims to turn a crab shell disposal cost into an income generating operation for this shellfish company. Specific objectives are to characterize the crab shell waste chemical composition, and then identify and test promising options to either use or dispose of crab shell waste as-is or to supply it for the development of other products. Using standard analytical methods operating within a major UK feed mill, analyses of a typical 1kg sample of the company’s crab shell waste found moisture and protein contents of 44.5% w/w and 10.0% w/w respectively, and a calcium content of 26.6 % w/w on a dry basis, which agreed with 2007 UK Sea Fish Industry Authority data. Three low added value options were selected for regulatory, economic and technical review, namely composting, land spreading (including initial treatment) and direct animal feeding. A simple 2plot trial for land spreading ex-cooked crab shell waste was carried out on grass land. A significant improvement in grass growth and weed reduction was shown. An acceptable soil conditioner incorporating the company’s crab shell waste was produced within a commercial compost plant, but without a cost saving to the company. The economics of turning crab shell waste into a possible poultry feed ingredient was found to require a tonnage 6 times higher than the company could supply. Further work continues on land spreading and composting, and other higher value options are being considered.