Exploitable fish waste and stranded beach debris in the Emilia-Romagna Region (Italy)

Sustainable production of biofuels and bioderivatives from aquaculture and marine waste

The annual global fish production reached a record 178 million tonnes in 2020, which continues to increase. Today, 49% of the total fish is harvested from aquaculture, which is forecasted to reach 60% of the total fish produced by 2030. Considering that the wastes of fishing industries represent up to 75% of the whole organisms, the fish industry is generating a large amount of waste which is being neglected in most parts of the world. This negligence can be traced to the ridicule of the value of this resource as well as the many difficulties related to its valorisation. In addition, the massive expansion of the aquaculture industry is generating significant environmental consequences, including chemical and biological pollution, disease outbreaks that increase the fish mortality rate, unsustainable feeds, competition for coastal space, and an increase in the macroalgal blooms due to anthropogenic stressors, leading to a negative socio-economic and environmental impact. The establishment of integrated multi-trophic aquaculture (IMTA) has received increasing attention due to the environmental benefits of using waste products and transforming them into valuable products. There is a need to integrate and implement new technologies able to valorise the waste generated from the fish and aquaculture industry making the aquaculture sector and the fish industry more sustainable through the development of a circular economy scheme. This review wants to provide an overview of several approaches to valorise marine waste (e.g., dead fish, algae waste from marine and aquaculture, fish waste), by their transformation into biofuels (biomethane, biohydrogen, biodiesel, green diesel, bioethanol, or biomethanol) and recovering biomolecules such as proteins (collagen, fish hydrolysate protein), polysaccharides (chitosan, chitin, carrageenan, ulvan, alginate, fucoidan, and laminarin) and biosurfactants.

Anaerobic digestion challenges and resource recovery opportunities from land-based aquaculture waste and seafood processing byproducts: A review

The unprecedented demand for seafood has resulted in land-based recirculating aquaculture systems (RAS), a highly intensive but sustainable fish farming method. However, intensification also results in concentrated waste streams of fecal matter and uneaten feed. Harvesting and processing vast quantities of fish also leads to the production of byproducts, further creating disposal challenges for fish farms. Recent research indicates that anaerobic digestion (AD), often used for waste treatment in agricultural and wastewater industries, may provide a viable solution. Limited research on AD of freshwater, brackish, and saline wastewater from RAS facilities and co-digestion of seafood byproducts has shown promising results but with considerable operational and process stability issues. This review discusses challenges to AD due to low solid concentrations, salinity, low carbon/nitrogen ratio, and high lipid content in the waste streams. Opportunities for recovering valuable biomolecules and nutrients through microbial treatment, aquaponics, microalgae, and polyhydroxyalkanoate production are also discussed.

Effect of different microbial seeds on batch anaerobic digestion of fish waste

Initial microbial compositions would be the precursor for the efficient anaerobic digestion (AD) of fish waste (FW). A mesophilic batch test was conducted using four seeds collected from different digesters treating various combinations of substrates to investigate their effects on FW degradation. Key microbial groups were identified by 16s rRNA gene-based metagenomics analysis. Among four, the seed from the digester co-digesting livestock manure, food waste, and food wastewater showed the best performance and obtained the highest methane yield (350.5 ± 5.2 mL/gVS_added) and lowest lag phase (0.6 ± 0.1 d). Proteiniphilum, Aminobacterium, dgA-11 gut group, and Syntrophomonas were dominant bacterial genera identified in FW degradation. Methanosaeta was the dominant methanogen in the best performing seed and microbial network analysis revealed its contribution to achieving the highest CH₄ yield. Obtained results could be useful in selecting microbial seed sources to avoid system imbalance in full-scale digesters that treat FW.

Stranded marine debris on the touristic beaches in the south of Bali Island, Indonesia: The spatiotemporal abundance and characteristic

Stranded marine debris (MD) has become a hot topic on Bali Island because it threatens coastal tourism sustainability. This study aims to investigate the spatiotemporal abundance and characteristics of MD on 14 touristic beaches in Bali Island. Sampling is carried out twice every season by adapting methods from NOAA's MD program. We found that the average MD abundance and weight were 0.356 ± 0.366 items/m² and 4.057 ± 3.892 g/m², respectively. Plastic dominated the MD based on abundance (86.9%) and weight (40.1%). Plastic bags, straws, and plastic cups are the most common items among plastics. The MD is originated from Indonesia and is dominated by land-based sources. The beaches are categorized as dirty in the rainy seasons and clean in the dry seasons. Statistically, the MD based on abundance, weight, category, source, and level of cleanliness varied significantly between seasons.

Quantification and mapping of fish waste in retail trade and restaurant sector: Experience in Emilia-Romagna, Italy

The circular economy approach imposes the complete recovery of components, materials and energy from waste. Many active compounds with biomedical and nutraceutical applications can be extracted by Fish Waste (FW), but few are the operating industrial plants. Quantification and mapping of the potential FW availability along the entire fish value-chain is crucial in fostering its actual valorisation. Apart at industrial processing, in the distribution segment the estimation of FW availability is absent. This paper aimed to quantify and locate FW generated by point sources such as supermarkets, fishmongers and restaurants as well as to establish the diffuse domestic FW production in a 4,5M inhabitants region. The study provides an exportable method and indications for comparable worldwide areas. A simplified valorisation scenario for equivalent biomethane production is also presented. Direct interviews and indirect approach based on fish consumption have been adopted and compared. Large supermarkets and medium-large restaurants are the main FW producers (239 and 125 kg/week, respectively) followed medium-large fishmongers and medium supermarkets (63 and 86 kg/week, respectively). In the investigated region the larger FW point sources are supermarkets (average 3000 Mg/y), while fishmongers are the smaller (average 750 Mg/y). Restaurants (average 1400 Mg/y) show the wider range of variability between 460 and 8000 Mg/y. The indirect methodology reveals that domestic FW production ranges from 2376 to 3961 Mg/y. Per capita estimations of FW ranged from 0.5 - 3 kg/y. The economic value of FW (biomethanation route) is 68 EUR/Mg. A qualification as "highly potential waste" would promote FW valorization.

Bioactive peptides from fisheries residues: A review of use of papain in proteolysis reactions

Papain is a cysteine endopeptidase of vegetal origin (papaya (Carica papaya L.) with diverse applications in food technology. In this review we have focused our attention on its application in the production of bio-peptides by hydrolysis of proteins from fish residues. This way, a residual material, that can become a contaminant if dumped without control, is converted into highly interesting products. The main bioactivity of the produced peptides is their antioxidant activity, followed by their nutritional and functional activities, but peptides with many other bioactivities have been produced. Thera are also examples of production of hydrolysates with several bioactivities. The enzyme may be used alone, or in combination with other enzymes to increase the degree of hydrolysis.

Fish and fish waste-based fertilizers in organic farming - With status in Norway: A review

This paper reviews relevant knowledge about the production and uses of fertilizers from fish and fish waste (FW) that may be applicable for certified organic farming, with a focus on crop and horticultural plants. Fish industries generate a substantial amount of FW. Depending on the level of processing or type of fish, 30-70% of the original fish is FW. Circular economy and organic farming concepts were used to evaluate the potential of production of fertilizers from captured fish. Fertilizers produced from captured fish promote the recycling of nutrients from the sea and back to terrestrial environments. Nutritional composition of FW is assessed to determine the potential to supply plant nutrients such as nitrogen, or a combination of nitrogen and phosphorous, or to enrich a compost. Methods used in processing of FW to produce fish- emulsion, fish hydrolysate/fish silage, fish-compost and digestate from anaerobic digestion/co-digestion are presented. Using information about commercially available fish-based fertilizers listed by the Organic Materials Review Institute (OMRI), we present a scenario for establishing fish/FW-based fertilizers industry and research in Europe. With Norway's 9th position among top ten global capture producers and focus in Norway on developing organic farming, we brief how FW is currently utilized and regulated, and discuss its availability for possible production of FW-based organic fertilizers. The amount of FW available in Norway for production of fertilizers may facilitate the establishment of an industrial product that can replace the currently common use of dried poultry manure from conventional farming in organic farming.