Fish mortality treatment and valorisation as a by-product: Environmental assessment of eco-innovation options

INTRODUCTION Based on environmental concerns, resource optimisation, and related European policies, the aquaculture sector is not exempt from seeking circular and less impacting solutions. The main technology to farmed fish mortality is currently represented by the ensilage. According to such approach, biomass is treated with formic acid, thus requiring flammable liquids to be transported and safely disposed of while exposing humans and the rest of the environment to threats. Some eco-innovations have been developed within the Horizon 2020 project GAIN – Green Aquaculture Intensification in Europe (2018–2021). Two of them, carried out by industrial partner Waister AS, were independently evaluated by the research partner Università Ca’ Foscari through a standardised well-oiled method for environmental assessment, and compared with business-as-usual. The eco-innovations’ gains, potentials, limits, and margins for improvement are here presented and discussed. MATERIALS AND METHODS This study presents the environmental assessment of three scenarios. Scenario A describes the leading business-as-usual approach for fish mortality treatment and disposal, i.e. ensilage. This requires formic acid to be used at the aquaculture premises, and flammable liquids to be transported away from the plant and to be disposed of (Baarset et al., 2020). The two eco-innovations that are here studied are aimed at avoiding to use formic acid in while processing fish mortalities. Ensilage is replaced by a superheated steam drying process through mechanical fluidisation. This is possible e.g. thanks to an eco-innovation machinery (Waister 15), able to dry and compact food waste. A dried sanitised product can be obtained for disposal or – better – valorisation as a by-product: this way, harmful waste is expected to become a resource as a secondary product to be re-circulated into the economy. In the selected eco-innovations, fish mortality is mixed with another by-product, i.e. local brewer’s spent grain, used as a structure material. In scenario B, water is used as a cooling medium; in scenario C, the cooling medium is replaced by a mix of glycol (30%) and water (70%). Some subscenarios are considered for B and C, based on different end-of-life options: simple disposal or reuse as a secondary product, i.e. as an ingredient in pet food. The adopted method for environmental accounting is represented by the standardised Life-Cycle Assessment (Arvanitoyannis, 2008; ISO, 2018). Indicators are available from different calculation choices, including the Ecological Footprint (Wackernagel and Rees, 2004), the Global Warming Potential, the Cumulative Exergy Demand, the Water Footprint (Hoekstra et al., 2011), and the ReCiPe sets (Goedkoop et al., 2009). RESULTS The two selected eco-innovations for mortality treatment seem to perform better than business-as-usual ensilage. Environmental gains larger than –80% are obtained in most indicators even when the product is simply disposed of. Smaller, neutral, and – according to the different calculation choices – sometimes opposing results are reached instead when talking about water consumption. Larger environmental gains arise from the reuse of the dried product in the processing of pet food, implying avoided disposal and savings in alternate ingredients. ACKNOWLEDGEMENTS The research leading to these results has received funding from the European Union’s HORIZON 2020 Framework Programme under Grant Agreement no. 773330. REFERENCES Arvanitoyannis, I. S. (2008). ISO 14040: life cycle assessment (LCA)–principles and guidelines. Waste management for the food industries, 97-132. Baarset, H., & Johansen, J. (2020). Innovative processes for mortality disposal in aquaculture. Deliverable 2.2. GAIN - Green Aquaculture INtensification in Europe. EU Horizon 2020 project grant nº. 773330. 14 pp. Goedkoop, M., Heijungs, R., Huijbregts, M., De Schryver, A., Struijs, J., & Van Zelm, R. (2009). ReCiPe 2008. A life cycle impact assessment method which comprises harmonised category indicators at the midpoint and the endpoint level, 1, 1-126. Hoekstra, A. Y., Chapagain, A. K., Mekonnen, M. M., & Aldaya, M. M. (2011). The water footprint assessment manual: Setting the global standard. Routledge. ISO - International Organization for Standardization (2018). ISO 14044:2018 Environmental management - Life cycle assessment - Requirements and guidelines. Wackernagel, M., & Rees, W. (2004). What is an ecological footprint?. The sustainable urban development reader, 211-219.