Elsevier

Aquacultural Engineering

Volume 77, May 2017, Pages 80-88
Aquacultural Engineering

Aquaponics and sustainability: The comparison of two different aquaponic techniques using the Life Cycle Assessment (LCA)

https://doi.org/10.1016/j.aquaeng.2017.03.002Get rights and content

Highlights

  • Floating system seems to be less impacting than the cultivation in gravel system.

  • The main environmental impacts were due to infrastructures, electricity and feed.

  • The use of renewable energies could reduce environmental impacts.

  • The optimization of management practices may reduce aquaponic impacts.

Abstract

Aquaponics is generally regarded as a sustainable practice, but its environmental burdens were not yet deeply investigated. In this study, Life Cycle Assessment (LCA) was used to assess the environmental impacts of two hypothetical coupled aquaponics systems (CAPS): Raft System (RAFT) and Media-Filled Beds System (MFBS). Rainbow trout (Oncorhynchus mykiss) and lettuce (Lactuca sativa) were considered as cultivated species in both systems. The Simapro© software V.8.0 was used for calculation. The comparison between the two virtual systems indicated the floating technique as the less impacting one. Even though energy consumption appears to be higher in the floating system, LCA results were markedly influenced by the extensive use of inert materials in MFSB. In both systems, contribution analyses underlined that the main environmental impacts are related to infrastructures, electricity and fish feed. The LCA analyses carried out in this study highlights that the choice of less impacting materials, and the optimization of management practices, should be taken as priorities in order to reduce environmental impacts of this activity.

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.

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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.

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