Valorization of Common Starfish (Asterias rubens) by Air Impingement Drying and Mesophilic Anaerobic Digestion: A Preliminary Study

The outbreak of common starfish A. rubens caused a 60% production loss of mussels in France. Three hundred tonnes of starfish were collected requiring further treatment in 2017. With composting and molecule extraction ending up in failure, an innovative solution coupling air impingement drying (AID) and anaerobic digestion (AD) was proposed to deal with this biomass. The AID kinetics of the starfish were studied at 40 °C and 70 °C. The dried starfish fragments were anaerobically digested at three Feed/Inoculum (F/I) ratios. The energy and economic balances were analyzed by varying system efficiencies. The equation of modified page could safely simulate the drying kinetics. The F/I ratio influenced the biogas production kinetics of starfish. In the most favorable case, the heat generated by the biogas from starfish could cover the heat demand for drying. The economic analysis proves that the valorization of bio-methane via cogeneration or injection into natural gas network could minimize treatment costs or even make profit from it. The AID-AD treatment of starfish was proved to be technically and economically feasible. The study offers basic protocols as a guidance for the mussel farmers to deal with the starfish outbreaks in the future.