Mass balance and energy optimisation in recirculating aquaculture systems (RAS), with focus on diurnal variations in water quality

Mass-balance and energy optimisation of RAS systems, with focus on diurnal variations in water quality. The number of aquaculture facilities with recirculation of water (RAS) is increasing, along with rapid technology development in this field. Building competence is important to ensure an environmentally sound and sustainable development, while safeguarding fish welfare. This project will address research questions concerning water quality, optimised operation, and implementation of sustainable energy. WP1: Variations in water quality give variable loading of cleansing systems, which can affect their effectiveness and subsequently fish welfare in RAS. Work package 1 will map diurnal variations and study how to safeguard fish welfare through adapted operation of these systems and through accurate measurement of water quality parameters. WP2: The energy intensive nature of recirculation aquaculture systems (RAS) hampers their sustainability and cost effectiveness. In Work package 2, energy supply systems will be scaled using dynamic simulation, while taking daily and seasonal variations to energy demand into account. Simulation will be based on a grid-independent energy supply, harvested from locally available renewable sources, such as wind, solar and wave energy, along with bioenergy recovered from the plant's waste. WP3: Increased utilisation of waste products will further improved energy efficiency, an idea that is central to a circular economy. Work package 3 will investigate the potential to recycle organic waste from the filter system into biogas. Thus generating competence that can contribute to increased energy recovery in RAS and reduction of the need for alternative waste management. This interdisciplinary project will contribute to build knowledge relevant to education and research in the fields of energy, ocean, environment, and aquaculture technology at the Western Norway University of Applied Sciences. This can also positively impact society and the environment. Two PhD-candidates have been recruited and has been accepted at relevant PhD-programs. Both are currently working on project planning and will primarily be working on WP1 (water quality in RAS) and WP2 (dynamic simulation) In WP1, until now, the focus has been on investigating and establishing relevant analytical methods, in addition to planning the first full scale study which will commence January 22. Bachelor students and a master student will have opportunity to join in this study. Positive synergy effects and increased competence building may be achieved through collaboration with other ongoing research projects during this study. The PhD period for the candidate working on WP2 has through additional internal (HVL) financing been extended to 4 years. Throughout this fall the candidate will work in collaboration with the research group on establishing a functional basic RAS model in Aspen HYSYS, linked to Matlab. A master student from the Ocean Technology study (HVL/UIB) will work on integrating metocean data in the model. In WP3 (sustainable use of sludge) experimental work has been performed spring 21. The study was performed by bachelor student from the chemical engineering study program I cooperation with HVL, Aquateam COWI and Bergen Municipality. This resulted in the bachelor thesis: The biochemical methane potential (BMP) in anaerobic digestion of sewage sludge with added fish sludge as co-substrate and associated heavy metal analysis of the digestate. During this fall, planning and preparations will be done to perform additional AMPTS experiments and pilot scale biogas experiments in spring 22. Bachelor students will be included in the experimental work.

New expertise is needed in the field of energy efficient aquaculture systems in general and in recirculating systems especially. The energy intensive nature of recirculation aquaculture systems (RAS) hampers their sustainability and cost effectiveness. By means of dynamic simulations using data collected in existing RAS, this interdisciplinary research project will study and optimise the energy use of RAS if supplied by locally available renewable energy forms like wind, wave and solar energy as well as biogas produced from accumulated sludge from the filter systems while taking diurnal variations in energy demand into account. There is also limited information regarding how both the biofilters and aerators function during diurnal fluctuations of water quality parametres. An understanding of the diurnal variations and better methods of measuring water quality parameters will help the fish farmers to run their fish farms better in relation to fish welfare and fish health. The carbon dioxide excretion from the fish results in acidification of the water in the rearing units and is comparable to increased carbon dioxide levels in the sea in the future. Thus, knowledge generated about this topic can also have important relevance beyond the field of aquaculture. Better utilization of waste and residual products is a central part of the circular economy, and can contribute to increased competitiveness and value creation in Norway. This project will further raise the research competence within utilisation of fish sludge to increase biogas production. Knowledge developed through this interdepartmental cooperation in the field of energy, ocean and aquaculture engineering is relevant to education and research at Western Norway University of Applied Sciences. The related industry will contribute to and profit from this research and the positive environmental and societal impact expected from the new knowledge.