Experimental study and sustainability assessment for fertilizers recovery from seafood waste

The increasing consumption of fish has led to an expansion of fish processing industry which in turn
has resulted in increasing quantities of by-products, which may represent up to the 70% of processed
fish and cause important management problems due to their susceptibility to rapid degradation. On
the other hand, seafood non-edible residues contain a considerable number of biomolecules (proteins,
polysaccharides etc.), and they can be used as starting products for the extraction of value-added
chemicals, like nitrogen-derived compounds, representing a good opportunity to mitigate the
environmental problems associated with their disposal.
In this context, under the SEA2LAND project, it has been studied the possibility to recover nutrients
from mollusks and fish wastes, collected respectively from the local companies Co.Pe.Mo. and Ittica
del Conero, in the form of protein hydrolysates (PHs) to be used as biostimulants for plants. In
particular, the process of enzymatic hydrolysis as method of production has been experimentally
studied at lab scale, taking into account the requirements provided by the reference legislation. Once
the best conditions have been evaluated, the Life Cycle Assessment (LCA) methodology has been
applied to determine the energy use and the potential environmental impacts associated with the
generation of this kind of product in a hypothetical pilot-scale plant. In addition, an economic
assessment has been also performed to determine the potential economic revenue, therefore the real
convenience of this kind of industrial pathway.
With the aim of optimizing the process also from the point of view of environmental and economic
efficiency, some operating conditions, although not the most optimal ones, have been preferred over
others. For what concerns the environmental assessment, it has been found that the production of
mollusks and/or fish based PHs has as most important impacts the fossil fuel depletion and the climate
change, mostly related to the use of electricity and thermal energy during hydrolysis and final
concentration. The impact on climate change resulted to be much lower in comparison with
chemically produced PH from leather wastes. The solution studied seems to be also highly
economically efficient, although uncertainties relating to investment costs should be taken into
account. Finally, it can be concluded that mollusks are the best choice in terms of waste valorization,
due to the lower environmental impact and, at the same time, very high the economic profit; however,
for protein hydrolysate production it seems preferable to use the mix (fish plus mollusks),
characterized by a medium environmental impact, and a profit closer to that of the mollusks.