The growing demand for seafood consumption had led to the increase of the seafood production from 134.3 million tonnes in 2004 to 170.9 million tonnes in 2016 leading to an increase of the by-products volume, which can account for 30–70% of whole seafood after industrial processing. Biorefinery concept, based on circular economy model, is developed to recover bio-based fertilizer transforming such by-products into nutrients. Mollusc waste (non-edible products) and fish waste (viscera, heads, bones, etc) are valorized in liming agent (calcium carbonate) for correction soil pH, in protein hydrolysate with biostimulant properties and in biochar for the enhancement of soil fertility and productivity.