Aquaponics and sustainability: The comparison of two different aquaponic techniques using the Life Cycle Assessment (LCA)
Introduction
Aquaponic could be defined as the integration of hydroponic vegetable cultivation into a recirculating fish aquaculture system (RAS). Conventional hydroponics requires mineral fertilizers in order to supply the plants with necessary nutrients but the aquaponic systems use the fish farming wastewater that is rich in fish waste as nutrient for plant growth (Goddek et al., 2015). Thus, plants associated with nitrifying bacteria provide a natural filter to remove dissolved nitrogen and phosphorous, controlling the accumulation of waste nutrients from fish culture (Al-Hafedh et al., 2008, Rakocy and Hargraves, 1993). From a general point of view, aquaponic systems could be divided into two basic sub-categories with respect to how nutrients are utilized: coupled aquaponic systems (CAPS) and decoupled aquaponic systems (DAPS). In CAPS, the two food production systems (aquatic animal farming and soilless plant farming) are coupled in a single loop (Reyes Lastiri et al., 2016). On the contrary, in DAPS fish and plants are integrated as separate functional units comprising individual water cycles that can be controlled independently (Goddek et al., 2016).
Many fish and vegetable species are potentially suitable to be farmed in aquaponics. However, the most common fish species are Nile tilapia (Oreochromis niloticus), rainbow trout (Onchorynchus mykiss), common carp (Cyprinus carpio) and African catfish (Clarias gariepinus) which can be integrated with leafy vegetables, such as lettuce (Lactuca sativa), basil (Ocimum basilicum), spinach (Spinacia oleracea) (Ako and Baker, 2009, Sace and Fitzsimmons, 2013, Goddek et al., 2015, Hu et al., 2015). Plant can be cultivated using raft systems (RAFT) and Media-Filled Beds Systems (MFBS). In the first ones, also called Deep Water Culture – DWC, vegetables are fixed in polystyrene boards flowing on top of the water, while in the second one the grow beds (GB) are filled with inert substrate (e.g. expanded clay, gravel or perlite), which supports plants and provides substrate for the microbial community.
In the last years, this practice has received considerable attention as a form of aquaculture suitable to produce marketable vegetable crops close to urban centres minimizing the water consumption (Love et al., 2015, Zou et al., 2016). In fact, when the system is maintained in a steady state, aquaponics works as a simple ecosystem: as a result it is considered environmental friendly and regarded as a sustainable agriculture practice (Blidariu and Grozea, 2011). Moreover, Hu et al. (2012) suggested that aquaponics, with concomitant nutrient recovery, will probably become one of the widely used methods of sustainable food production in the near future (Hu et al., 2012). Research in aquaponics began in the 1970s but only recently scientists started to investigate the sustainability of these systems by means of holistic approaches, such as those based on the Life Cycle Assessment (LCA) (Love et al., 2015, Xie and Rosentrater, 2015). LCA is a powerful tool to assess the environmental sustainability of a production, since it provides a comprehensive quantification of direct and indirect environmental impacts, from a macro perspective point of view (Foteinis and Chatzisymeon, 2016).
The aim of this study is to investigate the environmental impacts of two alternative aquaponic processes, namely RAFT and MFBS systems. In order to achieve this goal, we performed a cradle to gate LCA of two “virtual” farms, producing rainbow trout and lettuce using respectively deep water culture and media-filled beds.
Section snippets
Aquaponic systems description
We considered two “virtual” CAPS: a raft system (RAFT) and a Media-Filled Beds System (MFBS). Thus, we modelled two small-scale “virtual” farms (system total volume = 23.6 m3) with an annual production of about 4.6 tons of lettuce and 0.4 tons of fish. Both systems share a common structure, which is presented in Fig. 1. Water is pumped from the tank (T) (volume = 5 m3) into the biofiter (B) (volume = 0.78 m3) to start the nitrification process. A centrifugal separator (S) (volume = 0.5 m3) is used for the
RAFTS and MFBS
The comparison of the LCA performed on the two systems is presented in Fig. 4. For all the selected impact categories MFBS showed higher percentages of contribution. This difference in contribution is similar and clearer for AD (RAFT: 46.9%; MFBS: 53.1%), GWP (RAFT: 46.1%; MFBS: 53.9%), AC (RAFT: 44.4%; MFBS: 55.6%) and CED (RAFT: 46.8%; MFBS: 53.2%), while for EU the two values are closer (RAFT: 49.5%; MFBS: 50.5%). Results of the contribution analyses are presented in Fig. 5 for both the
Discussion
The LCA methodology has already proved to be a useful tool to evaluate the environmental burdens of both agricultural and aquaculture activities (Ayer and Tyedmers, 2008, Roque d’Orbcastel et al., 2009, Romero-Gámez et al., 2014, Santos et al., 2015, Foteinis and Chatzisymeon, 2016, Lourguioui et al., 2017). However, thus far, LCA was applied only to a specific small-scale aquaponic system (Love et al., 2015) or focusing on techno-economic analysis (TEA) (Xie and Rosentrater, 2015). In the
Conclusion
This study provides an assessment of the main environmental impacts linked to aquaponics, with particular reference to those techniques which are actually the most widely adopted by farmers approaching this innovative practice. The LCA analyses performed in this study underlined that the choice of less impacting materials and the optimization of management practices should be regarded as a priority in order to reduce environmental impacts deriving from this activity. According to the chosen
Andrea Alberto Forchino is a Ph.D. biologist specialized in aquaculture. Currently, he has a research fellow at the Ca’ Foscari University of Venice, in the Department of Environmental Sciences, Informatics and Statistics. One of the main topics of his research is the use of the Life Cycle Assessment to investigate the sustainability of the aquaculture processes, including aquaponics.
References (60)
- et al.
Assessment of the environmental impact of carnivorous finfish production systems using life cycle assessment
J. Clean. Prod.
(2009) - et al.
Comparative environmental performance of artisanal and commercial feed use in Peruvian freshwater aquaculture
Aquaculture
(2015) - et al.
Solid and suspended/dissolved waste (N, P, O) from rainbow trout (Oncorhynchus mykiss)
Aquaculture
(2011) - et al.
A study on the optimal hydraulic loading rate and plant ratios in recirculation aquaponic system
Bioresour. Technol.
(2010) - et al.
Aquaponic systems; nutrient recycling from fish wastewater by vegetable production
Desalination
(2009) - et al.
Aquatic worms eating waste sludge in a continuous system
Bioresour. Technol.
(2009) - et al.
Effect of plant species on nitrogen recovery in aquaponics
Bioresour. Technol.
(2015) - et al.
Energy and water use of a small-scale raft aquaponic system in Baltimore, Maryland, United States
Aquacult. Eng.
(2015) - et al.
Nutrient content in the muscle and skin of fillets from farmed rainbow trout (Oncorhynchus mykiss)
Food Chem.
(2015) - et al.
Life cycle assessment of cultivating lettuce and escarole in Spain
J. Clean. Prod.
(2014)
Comparative life cycle assessment (LCA) of raising rainbow trout (Oncorhynchus mykiss) in different production systems
Aquacult. Eng.
Comparing environmental impacts of native and introduced freshwater prawn farming in Brazil and the influence of better effluent management using LCA
Aquaculture
Global overview on the use of fish meal and fish oil in industrially compounded aquafeeds: trends and future prospects
Aquaculture
Effect of seasonal variation on nitrogen transformations in aquaponics of northern China
Ecol. Eng.
Enhance aquaculture sustainability utilizing by products
World Aquac. Soc.
Economic analysis of an aquaponics system for the integrated production of rainbow trout and plants
Int. J. Recirc. Aquacult.
Phytoremediation of aquaculture effluents
Aquaponics J.
Small-Scale Lettuce Production with Hydroponics or Aquaponics
Food production and water conservation in a recirculating aquaponics system in Saudi Arabia at different ratios of fish feed to plants
J. World Aquacult. Soc.
Assessing alternative aquaculture technologies: life cycle assessment of salmonid culture in Canada
J. Clean. Prod.
Aquaponic Gardening: A Step-By-Step Guide to Raising Vegetables and Fish Together
The effects of oxygen supplementation on growth and survival of rainbow trout (Oncorhynchus mykiss) in different stoking densities
Iran. J. Fish. Sci.
Increasing the economical efficiency and sustainability of indoor fish farming by means of aquaponics—review
J. Anim. Sci. Biotechnol.
Growth, development and yield of head lettuce cultivated on paper and polyethylene mulch
HortScience
Modelling the interactions between offshore fish cages and elemental biogeochemical cycles in the Mediterranean sea
Aquacult. Environ. Interact.
Growth performance, fillet quality and reproductive maturity of Rainbow Trout (Oncorhynchuss mikiss) cultured to 5 kilograms within Fresh Water Recirculating Systems
J. Aquacult. Res. Dev.
Better management practices for flow-through aquaculture systems
Life cycle assessment of organic versus conventional agriculture. A case study of lettuce cultivation in Greece
J. Clean. Prod.
Implementation of Life Cycle Impact Assessment Methods Ecoinvent Report 3
The environmental impact of the production of fresh cut salad: a case study in Italy
Int. J. Life Cycle Assess.
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Andrea Alberto Forchino is a Ph.D. biologist specialized in aquaculture. Currently, he has a research fellow at the Ca’ Foscari University of Venice, in the Department of Environmental Sciences, Informatics and Statistics. One of the main topics of his research is the use of the Life Cycle Assessment to investigate the sustainability of the aquaculture processes, including aquaponics.
Hichem Lourguioui is an assistant professor at ENSSMAL (National High School of Marine Sciences and Coastal Management, Algeria) specialized in marine aquaculture sustainability. He contributes to the assessment of the environmental impacts of marine aquaculture products using Life Cycle Assessment (LCA). He contributes under European projects (MEDINA, SMART) to the selection of potential suitable sites for marine aquaculture in Algeria.
Daniele Brigolin received his PhD in Environmental Sciences from the University Ca’ Foscari of Venice in 2008. Since 2012 he joined the Department of Environmental Sciences, Informatics and Statistics of the University of Venice as a researcher in Ecology with temporary appointment. His research activity is focused on the quantitative study of the direct and indirect effects of harvesting on ecosystem structure and dynamics. Particular attention was devoted to the sustainability of aquaculture productions, in the framework of the implementation of the ecosystem approach to aquaculture.
Roberto Pastres is Associate Professor of Environmental Chemistry at the Department of Environmental Sciences, Informatics and Statistics (Ca’ Foscari University of Venice). He currently teaches “Physical Chemistry” and “Mathematical tools for environmental scientist” to environmental science students. Since 1987, his research activity has mainly concerned the development of mathematical models for the analysis of transport, chemical and biological processes in coastal water bodies. More recently, his scientific interests have turned toward the modelling of bioaccumulation processes and sustainable aquaculture.