Scientific publications
– Publications –
Hydrolysis and thermochemical technologies for the recovery of bio-based fertiliser from fishery waste (UNIVPM)
Recovering nutrients from aquaculture industry by-products for the production of bio-based fertilizers (UVIC)
The aquaculture industry generates large quantities of animal by-products that need to be managed appropriately to minimize their potential health risk (EC1069/2009). The fish sludge, composed of fish feces and animal feed, requires a special attention since the fast growth of land-based aquaculture during the last years and the ever-increasing application of recirculating aquaculture systems have significantly increased the volume of sludge generated. The composition of the fish sludge, with a high content of nutrients and minerals, evinces its potential as a fertilizer product. Nevertheless, its direct use as a natural fertilizer is limited by governmental regulations, being necessary to examine suitable processes based on a holistic approach to produce agronomic value products. To overcome this challenge, in the framework of SEA2LAND project, BETA Technological Center is evaluating an innovative valorization system integrating technologies such as membrane systems, freeze concentration, biodrying, thermal treatment coupled to phosphorous-ash recovery and acid scrubber, to obtain products with agronomic value to be applied directly as bio-based fertilizers in field crops and others to be used as precursors for the formulation of tailor-made fertilizers. The fertilizing products obtained are: i) a nutrient-rich concentrate, ii) ammonium salts, iii) a phosphorous-rich organic amendment and, iv) phosphoric acid.
Experimental study and sustainability assessment for fertilizers recovery from seafood waste (UNIVPM)
ThermoMechanoChemical (TMC) fractionation of aquaculture by products by twin screw extrusion for the production of biobased fertilisers (CATAR)
Understanding the value of freshwater aquaculture and fish processing by-products through agroinnovative approach & technological solutions (CAVIAR)
Preliminary evidence of advanced bio-based fertilizer production and water reuse from fishery wastes (UNIVPM)
Seafood processing generates a huge amount of discards that can be used to recover valuable compounds. In this study, a biorefinery scheme is proposed to obtain calcium carbonate (liming agent), protein hydrolysates (biostimulant), biogas and a biochar-compost composite. Water would be also reused within the process, minimizing water footprint. From this scheme, 1 ton of raw waste could be valorized in 700 kg of a liming agent, 30 kg of biostimulant, 26 kg of biochar-compost composite and 1.2 Nm3 of methane.
Study of thermochemical co-treatment of seafood by-products and green waste towards alternative fertilizer production (UNIVPM)
In recent years the expansion of the fish processing industry caused by the increase in seafood consumption has led to a considerable increase in by-products (up to 70%), causing important management problems due to their degree of degradability. However, they can be valorised as bioproducts for agriculture as they are rich in nutrients, especially nitrogen, and others, representing a good opportunity to mitigate the environmental problems associated with their disposal.
In this context, in the frame of SEA2LAND project, the possibility to recover bio-based fertilizer from molluscs and fish wastes has been studied. These wastes were collected, respectively, from the local companies Co.Pe.Mo. and Ittica del Conero, to be then applied in agriculture as soil improvers or organic fertilizers, which is completely in line with the objective set by the European Commission to reduce the use of non-renewable sources in fertilizer production by 30%. The valorization technologies which were experimentally investigated in this study consisted of pyrolysis and composting with biochar addition. Legislative requirements and international quality standards were also analysed and taken into account.
As first step, lab-scale pyrolysis was performed in order to analyze the biochar obtained from different sources and assess its compliance with quality standards. Tests were carried out by mixing gardening waste, commonly used in pyrolysis due to the lignocellulosic matrix, and fish by-products. Results showed non-significant differences in the char produced at a physical level, but at a chemical level, a significant increase in the nitrogen content in the pyrolysed biomass with higher percentages of fish by-products was observed. However, at the same time an increase in the nickel content, exceeding the threshold values given by quality standards was also obtained. Analyses were also performed on the bio-oil and syngas produced during pyrolysis to understand how the presence of lignocellulosic material can interact with the fish.
After that, fish by-products were composted in a 30-L reactor with forced aeration by adding 10% of biochar to improve process performance such as the increase in biological activity, reduction of odor and GHG emissions, and minimization of Nitrogen loss. The temperature inside the reactor, oxygen and carbon dioxide in exhausted gas were monitored online as an indication of microbial activity and control of aeration strategy. Composting mixture was sampled once per week to determine the degree of biological stability and control process performance. The ammonia emissions produced during the test were compared to other composting tests performed without the addition of biochar, showing a significant reduction. It was corroborated by performing nitrogen mass balances taht the addition of biochar within the feedstock to be composted significantly reduced emissions, thus increasing the nitrogen content within the final product, which can improve its value as Nfertilizer.
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Biorefineries to improve water and resource recovery in the seafood processing industry (UNIVPM)
Food losses are responsible for noteworthy economic costs and negative environmental impacts. Within all the food-processing activities, seafood industry is of high importance, especially in coastal regions. Most seafood wastage is currently removed and discarded without recovering the valuable materials that it contains. However, seafood waste can be used as raw matter in biorefineries. Biorefineries refer to facilities where different conversion processes are integrated to obtain multiple bioproducts from organic feedstock. To this aim, different physical, chemical, thermochemical, and biological processes can be implemented to obtain biofertilizers, biostimulants, biofuels, and other value-added biocompounds. This chapter focuses on the theoretical implementation of biorefineries fed by wastes coming from the seafood industry. Some processes and technologies are reviewed, as well as some biocompounds that can be obtained from seafood wastes.
Social life cycle assessment of producing advanced bio-based fertilizers from fisheries/aquaculture wastes (INPT)
Techno-economic assessment of biorefinery schemes based on mollusc and fish wastes (UNIVPM)
Life cycle assessment (LCA) of bio based fertilizers from fisheries and aquaculture sidestreams (FIBL CH)
Production of biofertilizers from tuna cooking waters through membrane nanofiltration and enzymatic hydrolysis (AZTI)
Brine as side-stream is one of the main environmental problems in the wastewater generation in different food industry processes, as it is for the tuna canning sector. The treatment of brines is a universal challenge due to its operation complexity and cost issues. More than 70% of the tuna caught in the world is canned or otherwise prepared or preserved. Spain leads Europe’s production of canned seafood with more than 343,000 tonnes of product weight produced, valued at €1.5 billion. The Iberian country also produces 70% of the canned tuna processed in Europe. The ratio of spent brine used per unit of canned tuna is around 1-1.5 kg of brine/kg canned tuna. So that, the estimation for annual production of spent brine generation is around 300,000-500,000 tonnes. As the typical disposals of brine are discharges to the sea and is the management jointly with the rest of process side streams through wastewater treatment plants, and due to the high salinity, it causes, consequently, problems of inhibition in the effluent treatment, and poor performance in the final effluents. However, these brines are rich in valuable proteins.
On the other hand, fertilizer consumption in Europe increases annually by 3% to cover increasing agricultural demand. Most of the fertilisers used in Europe are imported, more than 3 million t are imported annually into the EU since 2015 (Fertilizers Europe, 2019). Several research studies have reported the benefits of protein hydrolysates as bio stimulants on the physiology of different plant crops (Colla G. et al. 2015). In this context, this study focuses on the concentration and desalting of the cooking brine of tuna and further enzymatic hydrolysis to produce free amino acids-based hydrolysate to be further used as an ingredient for the formulation of a new bio stimulant
Optimization of the autolysis of rainbow trout viscera for amino acid release using response surface methodology (AZTI)
2012 (Iñarra et al, 2018). The rise of the production of fish involves the rise of fish by-products, that in case of
being disposed could suppose an environmental risk. Fish viscera are part of the by-products used to produce
fishmeal and are the 10-18 % of the whole fish weight.
Fish silage or acid autolysis is commonly used in areas with high fisheries rates and consists of liquefaction
and stabilization of minced fish at room temperature, normally adding formic acid until reaching a pH between
3.5 and 4.5 to prevent microbial growth. Hydrolysis of proteins occurs thanks to the endogenous acid proteases
that are located at the fish viscera, which enable to get low molecular weight peptides and amino acids (Toppe et
al, 2018). The resulting protein hydrolysates could be used as fertilisers. However, silage can take several days to
achieve a high hydrolysis degree. In this work, autolysis has been carried out simulating the conditions of
enzymatic hydrolysis but only working with the endogenous enzymes from fish viscera with the aim of
accelerating a typical silage to get free amino acids while saving costs derived from the use of commercial
enzymes.
Quality and safety assessment of fertilising products derived from fishery waste and by-products (UGENT)
Fish and aquaculture industries offer great potential for valuable biobased fertilising products, which can be recovered from these industries’ side/waste streams to replace synthetic mineral fertilisers.
In this study, 24 potential fertilising products were collected from 7 pilot-sites in 6 countries which recovered nutrients from fishery waste and by-products using 9 different technologies within H2020 Project SEA2LAND, in which 10 of these products were qualified as organic fertiliser or growing media/soil improver.
Atlantic case: Fractionation of fish-farming by-products by twin-screw extrusion to produce biobased fertilisers (CATAR)
Presentation for the ESNI Conference 2023 about the Atlantic case of SEA2LAND Horizon 2020 Project.
Production of bio-based fertiliser from aquaculture sludge: the case of Mediterranean area in the framework of Sea2Land project (UVIC)
This work aims to valorize aquaculture sludges to obtain products with agronomic value to be applied directly as BBF in field crops and other to be used as precursors for the formulation of tailor-made fertilizers.
Consumer awareness and perceptions of the use of fish processing by-products in bio-fertilisers production (AZTI)
Nutrient recovery and recycling from fishery waste and by-products (UGENT)
Comparison of amino acid release between enzymatic hydrolysis and acid autolysis of rainbow trout viscera (AZTI)
Fish protein hydrolysates were obtained from cultured rainbow trout (Oncorhynchus mykiss) viscera using commercial and endogenous enzymes. Two methods were employed for hydrolysis: acid autolysis (also known as silage) at room temperature for 10 days in acidic conditions, until total solubilisation, and enzymatic hydrolysis using Alcalase 2.4 LFG, Protana Prime, and the endogenous enzymes in the viscera. The effectiveness of both methods in releasing free amino
acids (FAA) was assessed. After evaluating the results, the most effective enzymatic hydrolysis was optimized. The findings indicated that enzymatic hydrolysis with Alcalase, Protana Prime and endogenous enzymes combined for 7 h at a dose of 1% of protein, and a 7-day acid autolysis yielded the highest degree of hydrolysis (83.8% and 75.8%), a yield of FAA from viscera of 5.9% and 3.2%, and a yield of FAA from total protein of 71.3% and 52.5%, respectively. In conclusion, the use of commercial enzymes was more efficient in releasing amino acids, but endogenous enzymes showed a strong proteolytic capacity during acid autolysis, suggesting it also as a promising method to produce FAA-rich hydrolysates.
Sustainability of the Atlantic case in Sea2Land project: Industrial production of biobased fertilizers from fish by-products by twin-screw extrusion (INPT, CATAR)
For the Atlantic area case study, the project aims at producing BBF’s from fish by-products2 using ThermoMechanoChemical (TMC) fractionation by twin-screw extrusion. Configured as an extraction process, extrusion represents an industrial continuous process able to provide simultaneously a solid and a liquid fraction 3. The use of TMC process for fertilizers production is an innovative approach that enables the recovery of not only BBFs with an agronomic value but also fish oil to reach a ZERO-waste process. The Atlantic process was developed on the fractionation of heads and frames of Steelhead trout. The biorefinery scheme integrates the extruder as main technology but also includes pretreatment units and downstream processes. The process was developed from TRL4 to TRL7 corresponding to feed rate in fish by-products of 5-10 kg/h and 100-200 kg/h respectively. From 1000 kg fish by-products, 2 fertilizing products are obtained i) 263 kg of an organic solid BBF (9% N/DM), ii) 320 kg of a liquid organic BBF (11% N/DM). Their agronomic efficiency was tested in pot trials without formulation and the solid BBF was retained for field trials. In addition, the process generates about 80 kg of fish oil highly prized by the human food and animal feed sectors 4. Sustainability was assessed by studying the environmental and socio-economic impacts of products. Environmental impacts were economically allocated, and the relative prices of oil and BBFs have therefore a major influence. The inventory of all process inputs and outputs and the use of SIMAPRO software with the Ecoinvent enable the identification of hot spots, which are mainly the electricity used for waste extrusion and the drying of solid BBF. Impacts can be compared with those of an NPK fertilizer with a comparable mineral content. In the case of climate change, the impacts are similar, but BBF has around 70% lower impacts for terrestrial acidification and freshwater eutrophication. For the social part, UNEP methodology5 was applied. The supply chain was assessed using Social HotSpot Database (SHDB) and semi-specific data on the fishing and chemical sectors in France. It reveals the importance of responsible sourcing and of certain social indicators, particularly in the impact categories dealing with health and safety. Besides, the impact on local economy are studied and business plans are defined.
From pilot to industrial scale fractionation of fish by-products by twinscrew extrusion for the production of biobased fertilisers (CATAR)
The SEA2LAND project is a 4-year collaborative Innovation Action (IA) funded by the EU in the frame of the Horizon 2020 programme. Based on the circular economy model, SEA2LAND promotes the production of fertilisers in the EU from its own raw materials. This solution is expected to reduce the soil nutrient imbalance in Europe. The basis of the project is the regional production of bio-based fertilizers (BBF) from aquaculture and fishery by-products by developing dedicated demonstration pilots that can be replicated across Europe, boosting local growth.
Fish sludge as fertiliser (NIBIO)
Fish sludge is a residue from aquaculture, containing fish feces and feed spill. The composition of fish sludge depends on the raw material of fish feed and the fraction of feed spill, as well as the salinity of the water (marine/salty or brackish). Fish sludge is usually filtered, dewatered and dried. However, some fish sludge is also used in biogas production or composted and then used as fertilizers.
Fish sludge contains nitrogen, but mostly on organic form, and nutrient content is unbalanced (Brod et al. 2018). Anaerobic digestion increases nitrogen availability (Brod et al. 2017; Foereid et al. 2021). Most research so far has been performed in pot experiment or field experiments in Norway only, and with grain or grass as test crop. In the SEA2LAND project, fish sludge has been tested as fertilizer for broccoli in field experiments, repeated in five European countries (Norway, Estonia, Belgium, France and Spain). Pelleted fish sludge was tested in all countries, and a pelleted mixture of fish sludge and other products was tested in Norway. Application rate was determined based on nitrogen availability found in a preceding pot trial. However, in the field trials, performance varied widely between sites. The causes of this will be further investigated under controlled conditions. A pot trial comparing fish sludge and digestate of fish sludge on nitrogen utilization and greenhouse gas emissions is being performed. Results from the field trial and selected pot trials will be presented and discussed.
Bio-based fertilisers for the food of the future – from fishery waste to growing organic broccoli in the year 2095 (ULIEGE)
Poster presented at TERRA DAY in May 2024.
Fishery waste-derived organic fertilisers as alternatives for nitrogen fertilization (UGENT)
Fish and aquaculture industries offer great potential to recover valuable fertilising products from their waste streams using technologies such as bokashi fermentation, hydrolysis, and biodrying. This study explores the potential of utilizing organic fertilisers derived from fishery waste and by-products from six representative European fishery sectors as alternatives to synthetic nitrogen (N) fertilisers, thereby potentially lowering environmental impact related to global warming. Total N content of the organic fertilisers ranged from 1.9% to 9.8% by mass, predominately organic N. A four-month incubation experiment revealed that organic fertilisers containing easily degradable N sources, such as protein fraction and amino acids, exhibited a higher mineralization rate (49-66%) than the other fertilising products (10-35%), resulting in enhanced N availability in the short term. Since the biogenic C from organic fertilisers mineralization does not contribute to the net increase in atmospheric CO2 to life cycle assessment (Egene et al., 2022), we hypothesize that these organic fertilisers would have lower global warming potential compared to their synthetic counterpart. To test this hypothesis, a follow-up experiment will monitor the gaseous emissions of (CH4, N2O and NH3) from these organic fertilisers. Results of these experiments will provide insightful information for the agronomic value and environmental impact of utilising fishery waste-derived organic fertilisers as a potential replacement for synthetic fertilisers.
Fish sludge as fertiliser (NIBIO)
Fish sludge is a residue from aquaculture, containing fish feces and feed spill. The composition of fish sludge depends on the raw material of fish feed and the fraction of feed spill, as well as the salinity of the water (marine/salty or brackish). Fish sludge is usually filtered, dewatered and dried. However, some fish sludge is also used in biogas production or composted and then used as fertilizers.
Fish sludge contains nitrogen, but mostly on organic form, and nutrient content is unbalanced (Brod et al. 2018). Anaerobic digestion increases nitrogen availability (Brod et al. 2017; Foereid et al. 2021). Most research so far has been performed in pot experiment or field experiments in Norway only, and with grain or grass as test crop. In the SEA2LAND project, fish sludge has been tested as fertilizer for broccoli in field experiments, repeated in five European countries (Norway, Estonia, Belgium, France and Spain). Pelleted fish sludge was tested in all countries, and a pelleted mixture of fish sludge and other products was tested in Norway. Application rate was determined based on nitrogen availability found in a preceding pot trial. However, in the field trials, performance varied widely between sites. The causes of this will be further investigated under controlled conditions. A pot trial comparing fish sludge and digestate of fish sludge on nitrogen utilization and greenhouse gas emissions is being performed. Results from the field trial and selected pot trials will be presented and discussed.
The Atlantic case in Sea2Land project: optimization of the fractionation of twin-screw extrusion of fish by-products for the production of biobased fertilisers and fish oil (CATAR)
The SEA2LAND project is a 4-year collaborative Innovation Action (IA) funded by the EU in the frame of the Horizon 2020 programme. Based on the circular economy model, SEA2LAND promotes the production of fertilisers in the EU from its own raw materials. This solution is expected to reduce the soil nutrient imbalance in Europe. The basis of the project is the regional production of bio-based fertilizers (BBF) from fishery and aquaculture by-products by developing dedicated demonstration pilots that can be replicated across Europe, boosting local growth. 26 partners from 11 countries are participating in the project. 9 technologies are developed on the basis of 7 demonstration pilots implemented in 6 representative areas of the European fishing and aquaculture sectors.
For the Atlantic area case study, the project aims at producing BBF’s from fish by-products1 using ThermoMechanoChemical (TMC) fractionation by twin-screw extrusion as innovative process. TMC process is a continuous process, working at low liquid/solid ratios and able to provide a solid and a liquid fraction 2.
The use of TMC process for BBF’s production is an innovative approach that makes it possible to recover not only products with an agronomic value but also other components such as lipids to reach a ZERO-wasteprocess. The process was developed on the fractionation of heads and frames of Steelhead trout’s (Oncorhynchus mykiss), provided by a fish farm (Pisciculture Ispeguy, French Basque country). The N, P, K, and lipids contents in raw materials were respectively of 6.8%/DM, 1.4%/DM, 0.54%/DM and 42.5%/DM for heads and 6.9%/DM, 1.9%/DM, 0.62%/DM, 46.5%/DM for frames. The Atlantic pilot integrates the TMC extruder as principal technological unit but also includes pretreatment units and downstream processes.
The TMC fractionation process was optimized at lab scale studying the twin screw extruder configuration and the influence of temperature, screw profile, screw speed or enzymes introduction on the yield in BBF’s and the yield in lipids recovery and on BBF’s composition (total N and residual lipids). The process developed at lab scale at a feed rate of 5-10 kg/h was scaled to pilot scale at a feed rate of 20 kg/h and at an industrial pilot scale at a feed rate of 100-200 kg/h. Two fertilizing products were obtained for the Atlantic Area: i) an organic solid BBF (9% N/DM), ii) a liquid organic fertilizer (11% N/DM). Both were directly tested in pot trials without formulation and the solid BBF was retained for field trials. Moreover, the TMC process generates as highly valuable co-product an oily phase. This oil, rich in omega 3 (5.1% in EPA+DHA) but also in astaxanthin (11 mg/kg), a red carotenoid, could be used in food and feed sectors 3.
SLCA methodology applied to bio-based fertilizers from fisheries/aquaculture waste in the scope of the Sea2Land Project (INPT)
The basis of the project is the regional production of Bio-Bases Fertilisers (BBFs) by developing demonstration pilots that can be replicated across Europe, boosting local growth. The project proposes the implementation of 9 technologies in 7 cases in 6 representative areas of the fisheries sector (North, Baltic, Atlantic, Cantabrian, Mediterranean, Adriatic Sea). The technologies will be applied to different by-products, and they will produce several BBFs either for local crops and conditions, and others for exporting. Besides, the effects on soil biodiversity, environmental sustainability and the impact on social parameters and local economy will be studied and business plans will be defined. Finally BBFs from by-products will serve to partially replace imported nutrients for agriculture in Europe, contributing to reduce the negative environmental effects of the misuse of byproducts.
Turning Wastewater from the Tuna Canning Industry into Protein-Rich Biomass through the Culture of Marine Microorganisms (NEIKER)
Correct management of fish canning industry effluents is essential to avoid environmental impact, nutrient loss, and to achieve circularity within the sector. Brines, in particular, are difficult to treat using conventional methods due to their high salinity and organic load. As an alternative, halophilic microorganisms capable of degrading organic matter and utilizing it for growth offer an opportunity to valorize brines.
Objective: This study explores the feasibility of integrating brines from tuna canning plants into the cultivation of Thraustochytrids to produce protein-rich biomass that can be introduced into the agrifood sector’s value chain.
Nutrients recovery from marine aquaculture sludge through biodrying process (UVIC)
Presentation made for the 11th International Conference on Sustainable Solid Waste Management, organised in Rhodes, Greece, in June 2024.
Treatment of sludge produced in a recirculating aquaculture system: Test of different flocculants to improve the sedimentation of suspended solids (ABT)
Sludge management is a challenge in aquaculture as its release into the environment has an impact on natural ecosystems. The present research, carried out within the SEA2LAND project, focuses on developing methods to treat sludge produced in Recirculating Aquaculture Systems (RAS), in order to recover the solid fraction, and re-send the clean water to the fish tanks. Flocculation, is a common method to increase the size of the suspended solid and promote their precipitation. The aim of this study is to identify the most efficient flocculants for the treatment of sludge produced in RAS where Atlantic salmon (Salmo salar) and European seabass (Dicentrarchus labrax) are farmed.
A liming agent by recycling mollusc shells (UMIL)
The total EU fishery production amounted to around 4.5 million tonnes in 2022, of which 1.1 from aquaculture. This poses a challenge regarding the huge volume of wastes derived from seafood production and processing, in both economic and environmental terms. Anyway, these wastes contain valuable compounds that can be recovered in agriculture. The EU-funded SEA2LAND project, based on the circular economy model, explores the production of large-scale fertilisers in the EU from fishery and aquaculture wastes. In mollusc cultivation and fishery, the main waste is composed by shells, composed of CaCO3 and, at a lesser extent, of MgCO3, making them a promising source of liming agent for acidic soil correction. Several areas in Europe have low pH soils, due both to natural and anthropogenic processes, requiring lime distribution for agricultural production. Agricultural lime products are categorized as ‘EC Fertiliser Liming Materials’ in the EU Fertilizing Product Regulation (2022), the most used being ground limestone, dolomitic ground limestone, chalk, ground chalk, burnt lime and hydrated lime. However, although needed for soil quality and agricultural production, liming is often discarded due to its costs. The possibility to use waste products as liming agents allows to address both economic and environmental issues. The shellfish waste used in this work is a mixture of mussel, clam and murex shells discarded from a mollusc processing facility located in Ancona (Italy), whose production of discards accounts for about 1.4 ± 0.2 t·d-1. Waste was pre-treated by shredding the feedstock in the presence of water in a 1:3 (water: shellfish) ratio and the crushed shells (around 80% dry matter) were separated by gravity. The obtained shells were dried, milled and finally, sieved at 1 mm to obtain the liming agent with different particle sizes. These milled shells were first compared to reference liming agents (CaCO3 and CaO) in an incubation experiment to determine their effect on soil pH (UNI EN 14984:2006 method). Then the recycled liming agent was applied in two sites in northern Norway that needed liming, one with oceanic climate and one with more continental climate. The recycled liming agent was compared to conventional liming agent and no liming. Grass was sown at both sites. Results from the incubation trial suggest that the recycled liming agent has a high pH corrective power, similar to CaO and CaCO3. The results on soil pH and yield from the field trials will also be presented.
Nutrient availability and greenhouse gas emissions from bio-based fertilizers under controlled conditions (UGENT)
Fertilisers from fish processing and aquaculture waste can have similar or lower environmental impacts than mineral fertilisers but variation is high (FIBL CH, INPT, AZTI, ISQ)
The production of mineral fertilisers causes several sustainability issues: while the manufacturing of nitrogen fertilisers requires high energy input, phosphorus fertilisers depend on the extraction of phosphate rock from finite deposits (Zhang, Akyol, and Meers 2023). In a circular economy, fertiliser production should thus be shifted towards the valorisation of so far unused biowaste streams from various sources (Chojnacka, Moustakas, and Witek-Krowiak 2020; Zhang, Akyol, and Meers 2023). An increasingly important waste stream originates from fish processing and aquaculture production. In this study, we analyse the environmental impacts of the production and application of bio-based fertilisers (BBFs) produced from fish processing and aquaculture waste and compare them to the production and use of mineral fertiliser.
Fish discard valorisation into low carbon biochar-compost composite (UNIVPM)
Fish Viscera Hydrolysates and Their Use as Biostimulants forPlants as an Approach towards a Circular Economy in Europe: A Review (AZTI)
The Atlantic case in Sea2Land project: Pilot scale fractionation by twin-screw extrusion of fish by-products from 2 species for the production of high P-content bio-based fertilisers (CATAR)
The Sea2Land1 project is a 4-year collaborative Innovation Action (IA) funded by the EU in the frame of the Horizon 2020 programme. Based on the circular economy model, SEA2LAND promotes the production of bio-based fertilizers (BBF) in the EU from its own raw materials in order to reduce the soil nutrient imbalance in Europe. The basis of the project is the regional production of BBF from fishery and aquaculture byproducts by developing dedicated demonstration pilots that can be replicated across Europe, boosting local growth. 26 partners from 11 countries are participating in the project. 9 technologies are developed on the basis of 7 demonstration pilots implemented in 6 representative areas of the European fishing and aquaculture sectors. For the Atlantic area case study, the project aimed at producing BBF’s from fish byproducts2 using ThermoMechanoChemical (TMC) fractionation by twin-screw extrusion. The process was developed on the fractionation of 50/50 mix of heads/frames of Steelhead trout (ST) and efficiently transferred to the same mix of Sturgeon (S). Both species are interesting sources of nutrients: 7-8% N/DM, 2-4% P/DM and 0.5-1.0% K/DM but also contains between 40% and 50% of lipids. Configured as an extraction process, extrusion represents an industrial continuous process able to provide simultaneously a solid and a liquid fraction 3. The use of TMC process for fertilizers production is an innovative approach allowing the recovery of not only BBFs with an agronomic value but also fish oil to reach a ZERO-waste process. After process development and optimization at TRL4-5, pilot scale trials at TRL6 were achieved at a feeding rate of 20 kg/h in fish by-products. From 20 kg fish by-products, 2 fertilizing products are obtained for each specie. For ST, 4.2 kg of an organic solid BBF (9.4 N/DM; 19 % Lipids/DM), 6.7 kg of a liquid organic BBF (13.9% N/DM) and 2.0 kg of fish oil. For S, 4.0 kg of solid BBF (9.8% N/DM; 17% Lipids/DM), 6.2 kg of liquid
BBF (10.5% N/DM) and 1.3 kg of fish oil are obtained. Both extracted oils could be highly prized by the human food and animal feed sectors 4. The efficiency of the process was evaluated in terms of N, P, K recovery in the solid BBF fraction and oil recovery. For ST, nutrients recovery was: N > 90%, P > 97% and K > 80%. More than 50% of oil was also recovered. The solid BBF’s from ST was evaluated for pot and field trials. It is conformed in terms of nutrients, heavy metals and pathogens. It is considered as high Pavailable, medium N-available and good C/N ratio.
Enhancing the phosphorus availability in aquaculture-sludge based fertilizers using chemical and biological strategies (UVIC)
The fast-growing aquaculture industry, producing 46% of the global fish consumption, generates significant waste, including animal by-products and sludge, such as those coming from recirculating aquaculture systems (RAS). To comply with the New European Circular Economy Plan, this work assessed the production of valuable bio- based fertilisers (BBFs) from a starting biodrying process of RAS-sludge, coupled with different innovative post-processing technologies. The biodried RAS-sludge
demonstrated to have a substantial total P-content (4.31% as P2O5), but a low phosphorus bioavailability (15% of soluble phosphorus). Two strategies were proposed to tackle this issue: i) chemical and biological solubilisation of phosphorus; ii) thermal treatment and chemical phosphorus recovery from ash by acidic treatment.
The experimental design of phosphorus solubilisation trials directly with the biodried product were performed via incubation tests. Soil incubations (150 g of low-nutrient soil + 3 g of biodried product) were performed for 30 days in controlled temperature and humidity conditions. Chemical and biological solubilisation of phosphorus was assessed by adding either sulphuric acid (10% addition at 96% m/v) or biological inoculum composed by Pseudomonas putida at different dosing (104-106 CFU/g of soil).
After complete combustion of biodried RAS-sludge product, the acidic phosphorus extraction from ash was performed. First, a screening of optimal operational conditions was performed using different concentrations of sulphuric and citric acid (1 M, 0.75 M, 0.5 M and 0.25 M) at 1 to 20 ash to acid ratio. Concentration of acids was selected after the elemental analysis of ash and following the stoichiometric acid requirement (Donatello et al., 2010). After 2 h extraction at continuous stirring at ambient temperature (25oC), 80% of phosphorus recovery was achieved with the most concentrated sulphuric acid while over 50% was achieved with sulphuric acid at 0.25M. Over 40% of phosphorus was recovered with the most concentrated citric acid solution (1 M).
To conclude, this work demonstrated the satisfactory enhancement of the quality of RAS-sludge derived biodried product in terms of phosphorus availability.
Optimization of the autolysis of rainbow trout viscera for amino acid release using response surface methodology (AZTI)
Recycling saline wastewater from fish processing industry to produce protein-rich biomass from a Thraustochytrid strain isolated in the Basque Country (NEIKER)
This study explored the use of brines from tuna canneries as a nutrients source for the culture of a marine protist isolated from coastal waters of Bizkaia (Basque Country, Spain). The process yielded 5.5 g/L of biomass with 8 % of nitrogen (2.8 g/L protein) in 168 h. Although under control conditions the biomass achieved was 45 % higher, brine provided amino acids, vitamins and phosphate allowing the simplification of the culture medium to glucose, trace metals, water and brine. This reduced the cost of the medium by 90 % saving 40 % of water in the process. These results provided a revalorisation strategy for an industrial wastewater difficult to manage coupled to obtaining a protein-rich biomass.
Bio-based fertilisers for the food of the future – from fishery waste to growing organic broccoli in the year 2095 (ULIEGE)
Poster presented at the TERRA DAY event organised at Gembloux Agro-Bio Tech Faculty, in Belgium.
Agro-environmental Potential of Novel Organic Fertilizers Derived from Fishery Waste (UGENT)
The application of novel organic fertilizers derived from secondary raw materials has emerged as a promising sustainable agricultural practice in recent years. This study investigates the potential of organic fertilizers produced from fishery waste to be applied as alternatives for synthetic nitrogen (N) fertilizers through comprehensive soil incubation and pot experiments. The N content of eight selected organic fertilizers ranged from 1.9% to 9.8%, in which some of them were rich in labile N such as protein fractions and amino acids. In a 120-day incubation trial, six of these labile N-rich organic fertilizers demonstrated a superior mineralization rate of 49-66% compared to 10-35% for the other fertilizing products, showcasing a high concentration of readily degradable N fractions.
This increased mineralization led to enhanced N availability for crop, which is crucial for shortterm agricultural productivity. Remarkably, when applied to spinach at a fertilization rate of 170 kg N ha⁻¹, the tested organic fertilizers performed comparably to the synthetic fertilizer, resulting in similar yields and statistically non-significant differences in N use efficiency over two months of spinach growth. Additionally, a follow-up experiment assessed greenhouse gas emissions, especially N₂O, from soils amended with the fertilizers under high-water condition. Notably, solid organic fertilizers exhibited lower N₂O emissions (0.5%-2.0%) compared to the liquid ones (2.6%-4.5%) even when soil moisture content reached 70% of water-filled pore space, which in line with the previous field studies (Aguilera et al., 2013), where solid organic fertilizers emitted less N2O than the liquid organic fertilizers ). Overall, these circular fertilizers matched the N-supplying efficacy of synthetic fertilizers, offering a sustainable alternative. Notably, solid organic fertilizers outperformed the liquid ones in terms of N2O emissions, highlighting their potential for more environmentally friendly agricultural practices.
Recycling fishery waste into biobased fertilizers: Agronomic performance and soil health impacts (UGENT, METK)
Sustainability of bio-based fertilizers produced from aquaculture waste within the framework of the H2020 Sea2Land project (INPT)
Presentation made at the ESPP Workshop celebrated the 10-12 June 2025 in Bergen (Norway) & online. The workshop was on nutrient management in aquaculture feed, seafood processing and fish sludge valorisation.
Optimisation of operational parameters in laboratory-scale enzymatic protein hydrolysis of fishery waste for biostimulant production (UNIVPM)
The global fish production sector is crucial for food security, employment, and economic sustainability, with projected growth to 204 million tonnes by 2030. However, significant waste (25-30% of biomass) is produced, leading to environmental concerns and disposal costs. This study explores enzymatic protein hydrolysis (EPH) as a sustainable method for recovering valuable biomolecules from fish and mollusc waste, contributing to a circular economy. Various operational parameters, including temperature, pH, enzyme type, hydrolysis duration, enzyme-tosubstrate ratio, and substrate dilution, were investigated to optimise nitrogen recovery (NR) and crude protein (CP) yield. The results showed that most CP recovery occurred within the first four hours. Alcalase® at 60°C demonstrated enhanced NR compared to Protana Prime®, while pH adjustments had minimal impact, reducing the need for chemical control. A 1:1 substrate-to-water ratio resulted in a similar NR as that of 1:2 with reduced water quantity, and halving the enzyme dosage achieved comparable recovery, leading to cost savings. These findings suggest the potential for scaling up to pilot and industrial levels, with significant savings in energy, water, chemicals, and enzyme use. Future studies should assess biostimulant efficacy and economic feasibility at a larger scale.
Co-pyrolysis of fish with pruning waste for biochar production as an amendment for composite composting in the biorefinery scenario (UNIVPM)
The circular economy model encourages waste from linear process chains as feedstocks to recover bioproducts. To this end, biorefineries are gaining increased attention as they produce valuable products from biomasses by utilising different conversion processes [1]. Fishery industry residues can make suitable feedstock in coastal areas for implementing biorefineries as global production is expected to reach 204 million tonnes (Mt) by 2030 due to growing demands [2]. This leads to massive amounts of leftovers accounting for 30–70% of original fish, depending on processing requirements [3]. Companies pay discarding fees for the safe disposal of these leftovers. A company in Ancona, Italy, whose discards production accounts for 26 t.y-1, incurs annually 5720 € in disposal costs. However, being composed of a substantial amount of proteins, minerals, lipids, polysaccharides, vitamins etc., and recovering these biomolecules may not only close the loop in the fish industry but also mitigate environmental issues related to the seafood industry. Different valuable products can be recovered depending on treatment processes (composting, pyrolysis, enzymatic hydrolysis). This study aims to co-pyrolysis fish waste (FW) with pruning waste (PW) to obtain biochar as an amendment for downstream composite biochar compost to obtain compost soil amendment for application in the agricultural sector.
Different feedstock (FW, GW, PW shellfish, microalgae, enzymatic hydrolysis residues) were characterised using TGA analysis to evaluate their potential for biochar production. TGA analysis of FW showed around 67.2% weight loss in the organic fraction and low inorganic content, however, up to 80% moisture content. Although FW would make suitable feedstock for biochar production, their wet nature would require extensive energy demands for drying. Alternatively, co-pyrolysis with other feedstocks such as lignocellulosic green waste (GW) and PW biomass can overcome this drawback, as they are commonly used for thermochemical processes and TGA characterisation showed about 51.4% and 60.1% weight loss in organic fraction for GW and PW respectively. Lab scale pyrolysis tests simulating slow pyrolysis resulted in 39.8±8% biochar for 100% GW, whereas 36.5% biochar was obtained for 50: 50% (FW: GW). Similarly, 37±1.5% for 30: 70% (FW: GW) while only 26.9% biochar db was obtained for 100% FW. Biochar characterisation showed a FW: GW ratio higher than 30:70% exceeds the maximum limit for nickel concentration set by EU reg. (2019/1009).
To confirm the replicability and process scale-up, pilot-scale pyrolysis tests were performed using lab scale parameters: Temperature of 400℃, a heating rate of 5.33℃/min, at different residence times (RT) of 40, 50 and 57 minutes. Both fish and pruning waste were pretreated (ground and dried at 80℃ for 24 h) to reduce moisture content and particle size. Results showed that with increasing RT, biochar content increased, attributable to secondary reactions for biochar production. 55.9% biochar was obtained at a RT of 57 minutes. Whereas a decreasing trend was observed with reducing RT of 50 and 40 minutes (49.6% and 49.9% respectively). While biooil content showed an increasing trend (12.5-17.9%). Biochar and bio-oil are currently being characterised for physio-chemical properties and heavy metals analysis. Besides, the pH and EC of biochar were within the required limit set by Italian legislation (D.Lgs. 75/2010). More tests are ongoing to confirm to further optimise the pyrolysis process as well as syngas collection and characterisation. In conclusion, pilot tests show promising results for potential upscaling of the co-pyrolysis process for FW and PW for biochar production and subsequent addition to the downstream composite composting process to produce soil improvers for the agricultural sector.