Simon Goddek

Alyssa Joyce

Benz Kotzen

Gavin M. Burnell Editors

Aquaponics

Food Production

Systems

Combined Aquaculture and Hydroponic

Production Technologies for the Future

Aquaponics Food Production Systems

Simon Goddek

•

Alyssa Joyce

•

Benz Kotzen

•

Gavin M. Burnell

Editors

Aquaponics Food Production

Systems

Combined Aquaculture and Hydroponic

Production Technologies for the Future

Funded by the Horizon 2020 Framework Programme

of the European Union

Editors

Simon Goddek

Mathematical and Statistical Methods

(Biometris)

Wageningen University

Wageningen, The Netherlands

Alyssa Joyce

Department of Marine Science

University of Gothenburg

Gothenburg, Sweden

Benz Kotzen

School of Design

University of Greenwich

London, UK

Gavin M. Burnell

School of Biological, Earth

and Environmental Sciences

University College Cork

Cork, Ireland

ISBN 978-3-030-15942-9 ISBN 978-3-030-15943-6 (eBook)

https://doi.org/10.1007/978-3-030-15943-6

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Preface

It has been more than 45 years since the science ﬁction ﬁlm Soylent Green (1973)

ﬁrst appeared in cinemas. The movie was prescient for its time and predicted many

of our current environmental problems, including dying oceans, the greenhouse

effect, overpopulation, and loss of biodiversity. Even though we hope that humans

will not serve as a future nutrient source, the scenarios laid out in the movie are not

that far from being realised. As researchers and citizens, we realise our duty of care

to the environment and the rest of our world’s ever-growing population. We are

concerned that if we stand back and ignore the current trends in exploitation of

resources and methods of production that our paradise of a planet will be doomed or

at least far diminished, such that living on the sterile surfaces of the Moon or Mars

will seem like a pleasant alternative. Generations to come will and should hold us

individually and collectively responsible for the mess that we leave. The numerous

authors of this book are in a lucky as well as in an unfortunate posit ion, in that we can

either help to solve problems or be held responsible by future generations for being

part of the problem. When we started the COST Action FA1305 ‘The EU

Aquaponics Hub – Realising Sustainable Integrated Fish and Vege table Production

for the EU ’, aquaponics was a niche technology that, at an industrial scale, could not

compete with stand-alone hydroponics and aquaculture technologies. However,

aquaponics technology in the past decade has taken great leaps forward in efﬁciency

and hence economic viability through a wide range of technological advances. As

our ability to understand the environmental costs of industrial farming increases, we

are more capable of developing technologies to ensure that farming is more produc-

tive and less damaging to the environment. This positive outcome should be

bolstered by the very encouraging signs that although young people are statistically

not interested in being the farmers of the future, they do want to be future farmers if

technology is involved and they can adapt these technologies to live closer to urban

environments and have a better quality of life than in the rural past. Kids of all ages

are fascinated by technology, and it is no wonder as technology solve s many

problems. At the same time though, kids (perhaps less so with teenagers) are also

environmentally conscious and unders tand that the future of our planet lies in the

melding of nature and technology. Technology allows us to be more productive, and

although we have no certainty that we can and will effectively solve climate change,

we still have hope that there will be a future where people will be healthy and fed

with nutritious food. We, the authors of this book, realise that we are but small fry in

a world of much bigger ﬁsh (sometimes sharks), but we are more than hopeful,

indeed conﬁdent, that aquaponics has a role to play in the world’s future food

production.

Within the timeline of COST Action FA1305, our objective was to bring

aquaponics closer to the public and to raise awareness of alternative growing

methods. The Action’s Management Committee had 90 experts from 28 EU coun-

tries, 2 near neighbour countries, and 2 international partner countries. We organised

7 training schools in different parts of Europe, involving 92 trainees from 21 coun-

tries, and 20 STSMs were awarded to 18 early career researchers from 12 countries.

Most importantly, we published 59 videos based on the training schools, all of which

are freely available on YouTube ( https://www.youtube.com/EUAquaponicsHub).

Action members collaborated in writing 24 papers (19 of which are open access),

book chapters, monographs, and a white paper. The white paper identiﬁes eight key

recommendations based on the experience of the working group members, trends

within current research and entrepreneurship, and the directions being investigated

by ECIs. The recommendations are:

1. The promotion of continued research in aquaponics.

2. The development of ﬁnancial incentives to enable the commercialisation of

aquaponics.

3. The promotion of aquaponics as social enterprise in urban areas.

4. The promotion of aquaponics in the developing world and in refugee camps.

5. The development of EU-wide aquaponics legislation and planning guidance.

6. The development of aquaponics training courses in order to provide the necessary

skilled workforce to enable aquaponi cs to expand in the EU.

7. The development of stricter health and safety protocols, including ﬁsh welfare.

8. The establishment of an EU Aquaponics Association, in order to promote

aquaponics and aquaponics technology in the EU and to assist with knowledge

transfer, and the promotion of high production and produce standards in EU

aquaponics (Fig. 1).

The assembled knowledge and experience of the group is considerable, and it is

therefore appropriate to take the opportunity at the end of the 4-year COST project to

gather this into a book, which was originally proposed by Benz Kotzen and Gavin

M. Burnell at the start and then with Simon Goddek and Alyssa Joyce. We are

fortunate that Springer Nature particularly Alexandrine Cheronet has been enthusi-

astic about this publication and that the COST organisation has funded the book as

open access so that it is available for anyone to download. We see it as part of our

duty to ensure that as many people as possible can beneﬁt from the knowledge and

expertise. The book is the product of 68 researchers and practitioners from 29 coun-

tries (Australia, Austria, Belgium, Brazil, Croatia, Czech Republi c, Denmark, Fin-

land, France, Germany, Greece, Iceland, Ireland, Israel, Italy, Malta, the

vi Preface

Netherlands, North Macedonia, Norway, Portugal, Serbia, Slovenia, South Africa,

Spain, Sweden, Switzerland, Turkey, the United Kingdom, and the United States).

When asking the members of our COST Action as well as external experts whether

they were willing to contribute to this book, the response was overwhelming. Putting

a book together with 24 chapters within 1 year would not have been possible without

the coopera tive spirit of every single lead author and coauthor. The book is testament

to their knowledge and enthusiasm. We offer our warmest appreciation to our

scientiﬁc review committee including Ranka Junge (aquaponics and educ ation),

Lidia Robaina (ﬁsh feed), Ragnheidur Thorarinsdottir (commercial aquaponics),

Harry Palm (aquaponics and aquaculture systems), Morris Villarroel (ﬁsh welfare),

Haissam Jijakli (plant pathology), Amit Gross (aquaculture and recycling), Dieter

Anseeuw (hydroponics), and Charlie Shultz (aquaponics). We would also like to

thank all peer reviewers of the 24 chapters who improved the content of the chapters.

Finally, yet importantly, the editors would also like to thank their families and

partners who hav e been patient in the editing a large book such as this.

Wageningen, The Netherlands Simon Goddek

Gothenburg, Sweden Alyssa Joyce

London, UK Benz Kotzen

Cork, Ireland Gavin M. Burnell

February 2019

Fig. 1 Group picture of the COST group in Murcia, Spain, 2017

Preface vii

Acknowledgements

The editors, authors, and publishers would like to acknowledge the COST (European

Cooperation in Science and Technology) organisation (https://www.cost.eu) initially

for funding and supporting the 4-year COST Action 1305, ‘The EU Aquaponics Hub

– Realising Sustainable Integrated Fish and Vegetable Production for the EU’,which

was conceived and chaired by Benz Kotzen, University of Greenwich, and then ﬁnally

for contributing funds to this publication, making it open-source and available to all to

read. Without COST, who brought almost all of the authors together, in an amazing

project, this book would not have been written, and without their ﬁnal dissemination

contribution, this book would not be available to everyone. We also acknowledge and

greatly appreciate the support of Desertfoods International GmbH (www.desertfoods-

international.com) and Developonics asbl (www.developonics.com) for the additional

ﬁnancial support required to enable the publication to be open-source. Additionally we

applaud the efforts and great skill of Aquaponik Manufaktur GmbH (www.aquaponik-

manufaktur.de) for producing a cohesive and attractive set of illustrations for the book,

the Netherlands Organisation for Scientiﬁc Research (NWO; project number 438-17-

402) for supporting Simon Goddek in his editorial work and writing, and the Swedish

Research Council FORMAS grant 2017-00242 for similarly supporting Alyssa Joyce

whilst she undertook editorial work and writing on this book. Finally, the editors are

indebted to the enthusiasm and diligence of its authors, especially of the 22 lead

authors of the 24 chapters in their sterling efforts to get this remarkable book delivered

on time. A heartfelt well-done one and all!

Wageningen University, Wageningen,

The Netherlands

Simon Goddek

University of Gothenburg, Gothenburg,

Sweden

Alyssa Joyce

University of Greenwich, London, UK Benz Kotzen

University College Cork, Cork, Ireland Gavin M. Burnell

Contents

Part I Framework Conditions in a Resource Limited World

1 Aquaponics and Global Food Chal lenges .................... 3

Simon Goddek, Alyssa Joyce, Benz Kotzen, and Maria Dos-Santos

2 Aquaponics: Closing the Cycle on Limited Water, Land

and Nutrient Res ources .................................. 19

Alyssa Joyce, Simon Goddek, Benz Kotzen, and Sven Wuertz

3 Recirculating Aquaculture Technologies ..................... 35

Carlos A. Espinal and Daniel Matulić

4 Hydroponic Technologies ................................ 77

Carmelo Maucieri, Carlo Nicoletto, Erik van Os, Di eter Anseeuw,

Robin Van Havermaet, and Ranka Junge

Part II Speciﬁc Aquaponics Technology

5 Aquaponics: The Basics ................................. 113

Wilson Lennard and Simon Goddek

6 Bacterial Relationships in Aquaponics:

New Research Directions ................................. 145

Alyssa Joyce, Mike Timmons, Simon Goddek, and Timea Pentz

7 Coupled Aquaponics Systems ............................. 163

Harry W. Palm, Ulrich Knaus, Samuel Appelbaum,

Sebastian M. Strauch, and Benz Kotzen

8 Decoupled Aquaponics Systems ............................ 201

Simon Goddek, Alyssa Joyce, Sven Wuertz, Oliver Körner,

Ingo Bläser, Mich ael Reuter, and Karel J. Keesman

9 Nutrient Cycling in Aquaponics Systems ..................... 231

Mathilde Eck, Oliver Körner, and M. Haïssam Jijakli

10 Aerobic and Anaerobic Treatments for Aquaponic

Sludge Reduction and Mineralisation ....................... 247

Boris Delaide, Hendrik Monsees, Amit Gross, and Simon Goddek

11 Aquaponics Systems Modelling ............................ 267

Karel J. Keesman, Oliver Körner, Kai Wagner, Jan Urban,

Divas Karimanzir a, Thomas Rauschenba ch, and Simon Goddek

12 Aquaponics: Alternative Types and Approaches ............... 301

Benz Kotzen, Maurício Gustavo Coelho Emerenciano,

Navid Moheimani, and Gavin M. Burnell

Part III Perspective for Sustainable Development

13 Fish Diets in Aquaponics ................................. 333

Lidia Robaina, Juhani Pirhonen, Elena Mente, Javier Sánchez,

and Neill Goosen

14 Plant Pathogens and Control Strategies in Aquaponics .......... 353

Gilles Stouvenakers, Peter Dapprich, Sebastien Massart,

and M. Haïssam Jijakli

15 Smarthoods: Aquaponics Integrated Microgrids ............... 379

Florijn de Graaf and Simon Goddek

16 Aquaponics for the Anthropocene: Towards

a ‘Sustainability First’ Agenda ............................ 393

James Gott, Rolf Morgenstern, and Maja Turnšek

Part IV Management and Marketing

17 Insight into Risks in Aquatic Animal Health in Aquaponics ...... 435

Hijran Yavuzcan Yildiz, Vladimir Radosavljevic, Giuliana Parisi,

and Aleksandar Cvetkovikj

18 Commercial Aquaponics: A Long Road Ahead ................ 453

Maja Turnšek, Rolf Morgenstern, Iris Schröter, Marcu s Mergenthaler,

Silke Hüttel, and Michael Leyer

19 Aquaponics: The Ugly Duckling in Organic Regulation ......... 487

Paul Rye Kledal, Bettina König, and Daniel Matulić

20 Regulatory Frameworks for Aquaponics

in the European Union .................................. 501

Tilman Reinhardt, Kyra Hoevenaars, and Alyssa Joyce

21 Aquaponics in the Built Environment ....................... 523

Gundula Proksch, Alex Ianchenko, and Benz Kotzen

xii Contents

Part V Aquaponics and Education

22 Aquaponics as an Educational Tool ......................... 561

Ranka Junge, Tjasa Griessler Bulc, Dieter Anseeuw,

Hijran Yavuzcan Yildiz, and Sarah Milliken

23 Food, Sustainability, and Science Literacy in One Package?

Opportunities and Challenges in Using Aquaponics

Among Young People at School, a Danish Perspective .......... 597

Bent Egberg Mikk elsen and Collins Momanyi Bosire

24 Aquaponics and Social Enterprise .......................... 607

Sarah Milliken and Henk Stander

Contents xiii

About the Editors

Simon Goddek Simon is an expert in the ﬁeld of

multi-loop aquaponics systems and an ecopreneur. In

2014, Simon started his PhD in the faculty of environ-

mental engineering at the University of Iceland,

completing i t in the group Biobased Chemistry and

Technology at Wageningen University & Research

(the Netherlands). At the time of publication, he

is a postdoc in the Mathematical and Statistical

Methods group (Biometris), where he is involved in

several projects in Europe (i.e. CITYFOOD) and

Africa (e.g. desertfoods Namibia). His research focus

in aquaponics includes numerical system simulation

and modelling, decoupled multi-loop aquaponics sys-

tems, and anaerobic mineralization solutions.

Alyssa Joyce Alyssa is an assistant professor in the

Department of Marine Sciences (aquaculture) at the

University of Gothenburg, Sweden. In her group, sev-

eral researchers are focused on the role of bacterial

relationships in nutrient bioavailability and pathogen

control in aquaponics systems. She was one of the

Swedish representatives to the EU COST Network on

aquaponics and is a partner in the CITYFOOD project

developing aquaponics technology in urban

environments.

Benz Kotzen Benz is an associate professor and head

of Research and Enterprise in the School of Design,

University of Greenwich, London, and a consultant

landscape architect. He runs the rooftop Aquaponics

Lab at the University. He developed and was chair of

the EU Aquaponics Hub, whose remit was to raise the

state of the art of aquaponics in the EU and facilitate

collaborative aquaponics research. Urban agriculture

including vertical aquaponic systems and growing

exotic vegetables aquaponically and drylands restora-

tion are key ﬁelds of research.

Gavin M. Burnell Gavin is an emeritus professor at the

Aquaculture and Fisheries Development Centre, Uni-

versity College Cork, Ireland, and president of the

European Aquaculture Society (2018–2020). He has

been researching and promoting the concept of marine

aquaponics as a contribution to the circular economy

and sees an important role for this technology in out-

reach to urban communities. As a co-founder of

AquaTT and editor of Aquaculture International, he is

excited at the possibilities that aquaponics has in

research, education, and training across disciplines.

xvi About the Editors

Part I

Framework Conditions in a Resource

Limited World

Chapter 1

Aquaponics and Global Food Challenges

Simon Goddek, Alyssa Joyce, Benz Kotzen, and Maria Dos-Santos

Abstract As the world’s population grows, the demands for increased food pro-

duction expand, and as the stresses on resources such as land, water and nutrients

become ever greater, there is an urgent need to ﬁnd alternative, sustainable and

reliable methods to provide this food. The current strategies for supplying more

produce are neither ecologically sound nor address the issues of the circular econ-

omy of reducing waste whilst meeting the WHO’s Millennium Development Goals

of eradicating hunger and poverty by 2015. Aquaponics, a technology that integrates

aquaculture and hydroponics, provides part of the solution. Although aquaponics has

developed considerably over recent decades, there are a number of key issues that

still need to be fully addressed, including the development of energy-efﬁcient

systems with optimized nutrient recycling and suitable pathogen controls. There is

also a key issue of achieving proﬁtability, which includes effective value chains and

efﬁcient supply chain management. Legislation, licensing and policy are also keys to

the success of future aquaponics, as are the issues of education and research, which

are discussed across this book.

Keywords Aqua ponics · Agriculture · Planetary boundaries · Food supply chain ·

Phosphorus

S. Goddek (*)

Mathematical and Statistical Methods (Biometris), Wageningen University, Wageningen,

The Netherlands

e-mail: simon.goddek@wur.nl; simon@goddek.nl

A. Joyce

Department of Marine Science, University of Gothenburg, Gothenburg, Sweden

e-mail: alyssa.joyce@gu.se

B. Kotzen

School of Design, University of Greenwich, London, UK

e-mail: b.kotzen@greenwich.ac.uk

M. Dos-Santos

ESCS-IPL, DINÂMIA’CET, ISCTE-Institute University of Lisbon, Lisbon, Portugal

e-mail: mjpls@iscte-iul.pt

S. Goddek et al. (eds.), Aquaponics Food Production Systems,

https://doi.org/10.1007/978-3-030-15943-6_1

1.1 Introduction

Food production relies on the availability of resources, such as land, freshwater,

fossil energy and nutrients (Conijn et al. 2018), and current consumption or degra-

dation of these resources exceeds their global regeneration rate (Van Vuuren et al.

2010). The concept of planetary boundaries (Fig. 1.1) aims to deﬁne the environ-

mental limits within which humanity can safely operate with regard to scarce

resources (Rockström et al. 2009). Biochemical ﬂow boundaries that limit food

supply are more stringent than climate change (Steffen et al. 2015). In addition to

nutrient recycling, dietary changes and waste prevention are integrally necessary to

transform current production (Conijn et al. 2018; Kahiluoto et al. 2014). Thus, a

major global challenge is to shift the growth-based economic model towards a

Freshwater Use

Biosphere Integrity

Climate Change Novel Entities

Stratospheric

Ozone Depletion

Atmospheric

Aerosol Loading

Land-System

Change

Ocean AcidificationBiochemical Flows

Functional DiversityGenetic Diversity

Phosphorus Nitrogen

Safe Operating Space

Zone of Uncertainty High-Risk Zone

Not Yet Quantified

Possible Positive Impact of Aquaponics

Fig. 1.1 Current status of the control variables for seven of the planetary boundaries as described

by Steffen et al. (2015). The green zone is the safe operating space, the yellow represents the zone of

uncertainty (increasing risk), the red is a high-risk zone, and the grey zone boundaries are those that

have not yet been quantiﬁed. The variables outlined in blue (i.e. land-system change, freshwater use

and biochemical ﬂows) indicate the planetary boundaries that aquaponics can have a positive

impact on

4 S. Goddek et al.

balanced eco-economic paradigm that replaces inﬁnite growth with sustainable

development (Manelli 2016). In order to maintain a balanced paradigm, innovative

and more ecologically sound cropping systems are required, such that trade-offs

between immedi ate human needs can be balanced whilst maintaining the capacity of

the biosphere to provide the required goods and services (Ehrlich and Harte 2015).

In this context, aquaponics has been identiﬁed as a farming approach that,

through nutrient and waste recycl ing, can aid in addressing both planetary bound-

aries (Fig. 1.1) and sustainable development goals, particularly for arid regions or

areas with nonarable soils (Goddek and Körner 2019; Appelbaum and Kotzen 2016;

Kotzen and Appelbaum 2010). Aquaponics is also proposed as a solution for using

marginal lands in urban areas for food production closer to markets. At one time

largely a backyard technology (Bernstein 2011), aquaponics is now growing rapidly

into industrial-scale production as technical improvements in design and practice

allow for signiﬁcantly increased output capacities and production efﬁciencies. One

such area of evolution is in the ﬁeld of coupled vs. decoupled aquaponics systems.

Traditional designs for one-loop aquaponics systems comprise both aquaculture and

hydroponics units between which water recirculates. In such traditional syst ems, it is

necessary to make compromises to the conditions of both subsystems in terms of pH,

temperature and nutrient concentrations (Goddek et al. 2015; Kloas et al. 2015) (see

Chap. 7). A decoupled aquaponics system, however, can reduce the need for trade-

offs by separating the components , thus allo wing the conditions in each subsystem to

be optimized. Utilization of sludg e digesters is another key way of maximizing

efﬁciency through the reuse of solid wastes (Emerenciano et al. 2017; Goddek et al.

2018; Monsees et al. 2015). Although many of the largest facilities worldwide are

still in arid regio ns (i.e. Arabian Peninsula, Australia and sub-Saharan Africa) , this

technology is also being adopted elsewhere as design advances have increasingly

made aquaponics not just a water-saving enterprise but also an efﬁcient energy and

nutrient recycling system.

1.2 Supply and Demand

The 2030 Agenda for Sustainable Development emphasizes the need to tackle global

challenges, ranging from climate change to poverty, with sustainable food produc-

tion a high priority (Brandi 2017;UN2017). As reﬂected in the UN’s Sustainable

Development Goal 2 (UN 2017), one of the greatest challenges facing the world is

how to ensure that a growing global population, projected to rise to around 10 billion

by 2050, will be able to meet its nutritional needs. To feed an additional two billion

people by 2050, food product ion will need to increase by 50% globally (FAO 2017).

Whilst more food will need to be produced, there is a shrinking rural labour force

because of increasing urbanization (dos Santos 2016). The global rural population

has diminished from 66.4% to 46.1% in the period from 1960 to 2015 (FAO 2017).

Whilst, in 2017, urban population s represented more than 54% of the total world

population, nearly all future growth of the world’s population will occur in urban

1 Aquaponics and Global Food Challenges 5

areas, such that by 2050, 66% of the global population will live in cities (UN 2014).

This increasing urbanization of cities is accompanied by a simultaneously growing

network of infrastructure systems, including transportation networks.

To ensure global food security, total food production will need to increase by

more than 70% in the coming decades to meet the Millennium Development Goals

(FAO 2009), which include the ‘eradication of extreme poverty and hunger’ and also

‘ensuring environmental sustainability’. At the same time, food production will

inevitably face other challenges, such as climate change, pollution, loss of biodiver-

sity, loss of pollinators and degradation of arabl e lands. The se conditions require the

adoption of rapid technological adva nces, more efﬁcient and sustainable production

methods and also more efﬁcient and sustainable food supply chains, given that

approximately a billion people are already chronically malnourished, whilst agricul-

tural systems continue to degrade land, water and biodiversity at a global scale

(Foley et al. 2011; Godfray et al. 2010).

Recent studies show that current trends in agricultural yield improvements will

not be sufﬁcient to meet projected global food demand by 2050, and these further

suggest that an expansion of agricultural areas will be necessary (Bajželj et al. 2014).

However, the widespread degradation of land in conjunction with other environ-

mental problems appears to make this impossible. Agricultural land currently covers

more than one-third of the world’s land area, yet less than a third of it is arable

(approximately 10%) (World Bank 2018). Over the last three decades, the availabil-

ity of agricultural land has been slowly decreasing, as evidenced by more than 50%

decrease from 1970 to 2013. The effects of the loss of arable land cannot be

remedied by converting natural areas into farmland as this very often results in

erosion as well as habitat loss. Ploughing results in the loss of topsoil through wind

and water erosion, resulting in reduced soil fertility, increased fertilizer use and then

eventually to land degradation. Soil losses from land can then end up in ponds, dams,

lakes and rivers, causing damage to these habitats.

In short, the global population is rapidly growing, urbanizing and becoming

wealthier. Consequen tly, dietary patterns are also changing, thus creating greater

demands for greenhouse gas (GHG) intensive foods, such as meat and dairy prod-

ucts, with correspondingly greater land and resource requirements (Garnett 2011).

But whilst global consumption is growing, the world’s available resources, i.e. land,

water and minerals, remain ﬁnite (Garnett 2011). When looking at the full life-cycle

analysis of different food products, however, both Weber and Matthews (2008) and

Engelhaupt (2008) suggest that dietary shifts can be a more effective means of

lowering an average household’s food-related climate footprint than ‘buying

local’. Therefore, instead of looking at the reduction of suppl y chains, it has been

argued that a dietary shift away from meat and dairy products towards nutrition-

oriented agriculture can be more effective in reducing energy and footprints

(Engelhaupt 2008; Garnett 2011).

The complexity of demand-supply imbalances is compounded by deteriorating

environmental conditions, which makes food production increasingly difﬁcult

and/or unpredictable in many regions of the world. Agricultural practices cannot

only undermine planetary boundaries (Fig. 1.1) but also aggravate the persistence

6 S. Goddek et al.

and propagation of zoonotic diseases and other health risks (Garnett 2011). All these

factors resul t in the global food system losing its resilience and becoming increas-

ingly unstable (Suweis et al. 2015).

The ambitious 2015 deadline of the WHO’s Millennium Development Goals

(MDGs) to eradicate hunger and poverty, to improve health and to ensure environ-

mental sustainability has now passed, and it has become clear that providing

nutritious food for the underno urished as well as for afﬂuent populations is not a

simple task. In summary, changes in climate, loss of land and diminution in land

quality, incre asingly complex food chains, urban growth, pollution and other

adverse environmental conditions dictate that there is an urgent need to not only

ﬁnd new ways of growing nutritious food economically but also locate food pro-

duction facilities closer to consumers. Delivering on the MDGs will require changes

in practice, such as reducing waste, carbon and ecological footprints, and aquaponics

is one of the solutions that has the potential to deliver on these goals.

1.3 Scientiﬁc and Technological Challenges in Aquaponics

Whilst aquaponics is seen to be one of the key food production technologies which

‘could change our lives’ (van Woensel et al. 2015), in terms of sustainable and

efﬁcient food production, aquaponics can be streamlined and become even more

efﬁcient. One of the key problems in conventional aquaponics systems is that the

nutrients in the efﬂuent produced by ﬁsh are different than the optimal nutrient

solution for plants. Decoupled aquaponics systems (DAPS), which use water from

the ﬁsh but do not retur n the water to the ﬁsh after the plants, can improve on

traditional designs by introducing mineralization components and sludge bioreactors

containing microbes that convert organic matter into bioavailable forms of key

minerals, especially phosphorus, magnesium, iron, manganese and sulphur that are

deﬁcient in typical ﬁsh efﬂuent. Contrary to mineralization components in one-loop

systems, the bioreactor efﬂuent in DAPS is only fed to the plant component instead

of being diluted in the whole system. Thus, decoupled systems that utilize sludge

digesters make it possible to optimize the recycling of organic wastes from ﬁsh as

nutrients for plant growth (Goddek 2017; Goddek et al. 2018). The wastes in such

systems mainly comprise ﬁsh sludge (i.e. faeces and uneaten feed that is not in

solution) and thus cannot be delivered directly in a hydroponics system. Bioreactors

(see Chap. 10) are therefore an important component that can turn otherwise

unusable sludge into hydroponic fertilizers or reuse organic wastes such as stems

and roots from the plant production component into biogas for heat and electricity

generation or DAPS designs that also provide independently controlled water

cycling for each unit, thus allowing separation of the systems (RAS, hydroponic

and digesters) as required for the control of nutrient ﬂows. Water moves between

components in an energy and nutrient conserving loop, so that nutrient loads and

ﬂows in each subsystem can be monitored and regulated to better match downstream

requirements. For instance, phosphorous (P) is an essential but exhaustible fossil

1 Aquaponics and Global Food Challenges 7

resource that is mined for fertilizer, but world supplies are currently being depleted at

an alarming rate. Using digesters in decoupled aquaponics systems allows microbes

to convert the phosphorus in ﬁsh waste into orthophosphates that can be utilized by

plants, with high recovery rates (Go ddek et al. 2016, 2018).

Although decoupled systems are very effective at reclaiming nutrients, with near-

zero nutrient loss, the scale of production in each of the units is important given that

nutrient ﬂows from one part of the system need to be matched with the downstream

production potential of other compo nents. Modelling software and Supervisory

Control and Data Acquisition (SCADAS) data acquisition systems therefore become

important to analyse and report the ﬂow, dimensions, mass balances and tolerances

of each unit, making it possible to predict physical and economic parameters

(e.g. nutrient loads, optimal ﬁsh-plant pairings, ﬂow rates and costs to maintain

speciﬁc environmental parameters). In Chap. 11, we will look in more detail at

systems theory as applied to aquaponics systems and demonstrate how modelling

can resolve some of the issues of scale, whilst innovative technological solutions can

increase efﬁciency and hence proﬁtability of such systems. Scaling is important not

only to predict the economic viability but also to predict production outputs based on

available nutrient ratios.

Another important issue, which requires further development, is the use and reuse

of energy. Aquaponics systems are energy and infrastructure intensive. Depending

on received solar radiation, the use of solar PV, solar thermal heat sources and (solar)

desalination may still not be economically feasible but could all be potentially

integrated into aquaponics systems. In Chap. 12, we presen t information about

innovative technical and operational possibilities that have the capacity to overcome

the inherent lim itations of such systems, including exciting new opportunities for

implementing aquaponics systems in arid areas.

In Chap. 2, we also discuss in more detail the range of environmental challenges

that aquaponics can help address. Pathogen control, for instance, is very important,

and contained RAS systems have a number of environmental advantages for ﬁsh

production, and one of the advantages of decoupled aquaponics systems is the ability

to circulate water between the components and to utilize independent controls

wherein it is easier to detect, isolate and decontaminate individual units when

there are pathog en threa ts. Probiotics that are beneﬁcial in ﬁsh culture also appear

beneﬁcial for plant production and can increase production efﬁciency when circu-

lated within a closed system (Sirakov et al. 2016). Such challenges are further

explored in Chap. 5, where we discuss in more detail how innovation in aquaponics

can result in (a) increased space utilization efﬁciency (less cost and materials,

maximizing land use); (b) reduced input resources, e.g. ﬁshmeal, and reduced

negative outputs, e.g. was te discharge; and (c) reduced use of antibiotics and

pesticides in self-contained systems.

There are still several aquaponic topic areas that require more research in order to

exploit the full potential of these systems. From a scientiﬁc perspective, topics such

as nitrogen cycling (Chap. 9), aerobic and anaerobic remineralization (Chap. 10),

water and nutrient efﬁciency (Chap. 8), optimized aquaponic ﬁsh diets (Chap. 13)

and plant pathogens and control strategies (Chap. 14) are all high priorities.

8 S. Goddek et al.

In summary, the following scientiﬁc and technological challenges need to be

addressed:

1. Nutrients: As we have discussed, systems utilizing sludge digesters make it

possible to optimize the recycling of organic waste from ﬁsh into nutrients for

plant growth, such designs allow for optimized reclamation and recycling of

nutrients to create a near-zero nutrient loss from the system.

2. Water: The reuse of nutrient-depleted water from greenhouses can also be

optimized for reuse back in the ﬁ sh component utilizing condensers.

3. Energy: Solar-powered designs also improve energy savings, particularly if

preheated water from solar heaters in the greenhouses can be recirculated back

to ﬁsh tanks for reuse.

The ability to recycle water, nutrients and energy makes aquaponics a potentially

unique solution to a number of environmental issues facing conventional agriculture.

This is discussed in Chap. 2.

1.4 Economic and Social Challenges

From an economic perspective, there are a number of limitations inherent in

aquaponics systems that make speciﬁc commercial designs more or less viable

(Goddek et al. 2015; Vermeulen and Kam stra 2013). One of the key issues is that

stand-alone, independent hydroponics and aquaculture systems are more productive

than traditional one-loop aquaponics systems (Graber and Junge 2009), as they do

not require trade-offs between the ﬁsh and plant components. Traditional, classic

single-loop aquaponics requires a compromise between the ﬁsh and plant compo-

nents when attempting to optimize water quality and nutrient levels that inherently

differ for the two parts (e.g. desired pH ranges and nutrient requirements and

concentrations). In traditional aquaponics systems, savings in fertilizer requirements

for plants do not make up for the harvest shortfalls caused by suboptimal conditions

in the respective subsystems (Delaide et al. 2016).

Optimizing growth conditions for both plants (Delaide et al. 2016; Godd ek and

Vermeulen 2018) and ﬁsh is the biggest challenge to proﬁtability, and current results

indicate that this can be better achieved in multi-loop decoupled aquaponics systems

because they are based on independent recirculating loops that involve (1) ﬁsh,

(2) plants and (3) bioreactors (anaerobic or aerobic) for sludge digestion and a

unidirectional water (nutrient) ﬂow, which can improve macro- and micro-nutrient

recovery and bioavailability, as well as optimization of water consumption (Goddek

and Keesman 2018). Current studies show that this type of system allows for the

maintenance of speciﬁc microorganism populations within each compartment for

better disease management, and they are more economically efﬁcient in so much as

the systems not only reduce waste outﬂow but also reutilize otherwise unusable

sludge, converting it to valuable outputs (e.g. biogas and fertilizer).

1 Aquaponics and Global Food Challenges 9

Independent, RAS systems and hydroponics units also have a wide range of

operational challenges that are discussed in detail in Chaps. 3 and 4. Increasingly,

technological advances have allowed for higher productivity rati os (Fig. 1.2), which

can be deﬁned as a fraction of the system’s outputs (i.e. ﬁsh and plants) over the

system’s input (i.e. ﬁsh feed and/or additional fertilization, energy input for lighting,

heating and pumpi ng CO

dosing and biocontrols).

When considering the many challenges that aquaponics encounters, production

problems can be broadly broken down into three speciﬁc themes: (1) system pro-

ductivity, (2) effective value chains and (3) ef ﬁcient supply chain management.

System Productivity Agricultural productivity is measured as the ratio of agricul-

tural outputs to agricultural inputs. Traditional small-scale aquaponics systems were

designed primarily to address environmental considerations such as water discharge,

water inputs and nutrient recycling, but the focus in recent years has increasingly

shifted towards economic feasibility in order to increase productivity for large-scale

farming applications. However, this will require the productivity of aquaponics

systems to be able to compete economically with independent, state-of-the-art

hydroponics and aquaculture systems. If the concept of aquaponics is to be success-

fully appli ed at a large scale, the reuse of nutrients and energy must be optimized, but

end markets must also be considered.

Effective Value Chains The value chains (added value) of agricultural products

mainly arise from the processing of the produce such as the harvested vegetables,

fruits and ﬁsh. For example, the selling price for pesto (i.e. red and green) can be

more than ten times higher than that of the tomatoes, basil, olive oil and pine nuts. In

addition, most processed food product s have a longer shelf life, thus reducing

spoilage. Evidently, fresh produce is important because nutritional values are mostly

higher than those in the processed foods. However, producing fresh and high-quality

produce is a real challenge and therefore a luxury in many regions of the world.

Losses of nutrients during stor age of fruit and vegetables are substantial if they are

not canned or frozen quickly (Barrett 2007; Rickman et al. 2007). Therefore, for

large-scale systems , food processing should at least be considered to balance out any

ﬂuctuations between supply and demand and reduce food waste. With respect to

food waste reduction, vegetables that do not meet fresh produce standards, but are

still of marketable quality, should be processed in order to reduce postharvest losses.

Input Products

Resource

Utilization

Waste

Fig. 1.2 An aquaponics

system seen as a black box

scheme. We do not get to

see inside the box, but we

know the inputs, the outputs

(i.e. ﬁsh and plants) and the

waste

10 S. Goddek et al.

Although such criteria apply to all agricultural and ﬁsheries products, value adding

can substantially increase the proﬁtability of the aquaponi cs farm, especially if

products can reach niche markets.

Efﬁcient Supply Chain Management In countries with well-developed transpor-

tation and refrigeration networks, fruit and vegetables can be imported from all

around the world to meet consumer demands for fresh produce. But as mentioned

previously, high-quality and fresh produce is a scarce commodity in many parts of

the world, and the long-distance movement of goods – i.e. supply chain management

– to meet high-end consumer deman d is often criticized and justiﬁably so. Most

urban dwellers around the world rely on the transport of foods over long distances to

meet daily needs (Grewal and Grewal 2012). One of the major criticisms is thus the

reliance on fossil fuels requi red to transport products over large distances (Barrett

2007). The issue of food miles directs focus on the distance that food is transported

from the time of production to purchas e by the end consumer (Mundler and Criner

2016). However, in terms of CO

emissions per tonne/km (tkm), one food mile for

rail transportation (13.9 g CO

/tkm) is not equal to one food mile of truck/road

transportation, as truck transportation has more than 15 times greater environmental

impact (McKinnon 2007). Therefore, transport ation distance is not necessarily the

only consideration, as the ecological footprint of vegetables grown on farms in rural

areas is potentially less than the inputs required to grow food in greenhouses closer

to urban centres.

Food miles are thus only a part of the picture. Food is transported long distances,

but the greenhouse gas emissions associated with food production are dominated by

the production phase (i.e. the impact of energy for heating, cooling and lighting)

(Engelhaupt 2008; Weber and Matthews 2008). For example, Carlsson (1997)

showed that tomatoes imported from Spain to Sweden in winter have a much

lower carbon footprint than those locally grown in Sweden, since energy inputs to

greenhouses in Sweden far outweigh the carbon footprint of transportation from

Spain. When sourcing food, the transport of goods is not the only factor to take into

consideration, as the freshness of products determines their nutritive value, taste and

general appeal to consumers. By growing fresh food locally, many scholars agree

that urban farming could help secure the supply of high-quality produce for urban

populations of the future whilst also reducing food miles (Bon et al. 2010; dos Santos

2016; Hui 2011). Both areas will be discussed in more detail in Sect. 1.5.

From a consumer’s perspective, urban aquaponics thus has advantages because of

its environmental beneﬁts due to short supply chains and since it meets consum er

preferences for high-quality locally produced fresh food (Miličić et al. 2017).

However, despite these advantages, there are a number of socio-economic concerns:

The major issue involves urban property prices, as land is expensive and often

considered too valuable for food production. Thus, purchasing urban land most

likely makes it impossible to achieve a feasible expected return of investment.

However, in shrinking cities, where populations are decreasing, unused space

could be used for agricultural purpose (Bontje and Latten 2005; Schilling and

Logan 2008) as is the case in Detroit in the United States (Mogk et al. 2010).

1 Aquaponics and Global Food Challenges 11

Additionally, there is a major issue of urban planning controls, where in many cities

urban land is not designated for agricultural food production and aquaponics is seen

to be a part of agriculture. Thus, in some cities aquaponic farming is not allowed.

The time is ripe to engage with urban planners who need to be convinced of the

beneﬁts of urban farms, which are highly productive and produce fresh, healthy,

local food in the midst of urban and suburban development.

1.5 The Future of Aquaponics

Technology h as enabled agricultural productivity to grow exponentially in the last

century, thus also supporting signiﬁcant population growth. However, these changes

also potentially undermine the capacity of ecosystems to sustain food production, to

maintain freshwater and forest resources and to help regulate climate and air quality

(Foley et al. 2005).

One of the most pressing challenges in innovative food production, and thus in

aquaponics, is to address regulatory issues constraining the expansion of integrated

technologies. A wide range of different agencies have jurisdiction over water, animal

health, environmental protection and food safety, and their regulations are in some

cases contradictory or are ill-suited for complex integrated systems (Joly et al. 2015).

Regulations and legislation are currently one of the most confus ing areas for pro-

ducers and would-be entrepreneurs. Growers and investors need standards and

guidelines for obtaining permits, loans and tax exemptions, yet the confusing

overlap of responsibilities among regulatory agencies highlights the urgent need

for better harmonization and consistent deﬁnitions. Regulatory frameworks are

frequently confusing, and farm licensing as well as consumer certiﬁcation remains

problematic in many countries. The FAO (in 2015), the WHO (in 2017) and the EU

(in 2016) all recent ly began harmonizing provisions for animal health/well-being

and food safety withi n aquaponics systems and for export-import trade of aquaponic

products. For instance, several countries involved in aquaponics are lobbying for

explicit wording within the Codex Alimentarius, and a key focus within the EU,

determined by the EU sponsored COST Action FA1305, the ‘EU Aquaponics Hub’,

is currently on deﬁning aquaponics as a clear and distinct entity. At present,

regulations deﬁne production for both aquaculture and hydroponics, but have no

provisions for merging of the two. This situation often creates excessive bureaucracy

for producers who are required to license two separate operations or whose national

legislation does not allow for co-culturing (Joly et al. 2015). The EU Aquaponics

Hub, which has supported this publication (COST FA1305), deﬁnes aquaponics as

‘a production system of aquatic organisms and plants where the majority (> 50%) of

nutrients sustaining the optimal plant growth derives from waste originating from

feeding the aquatic organisms’ (see Chap. 7).

Consumer certiﬁcation schemes also remain a difﬁcult area for aquaponics pro-

ducers in many parts of the world. For instance, in the United States and Australia,

aquaponic products can be certiﬁed as organic, but not within the European Union.

12 S. Goddek et al.

From an economic perspective, aquaponics is in theory capable of increasing the

overall value of ﬁsh farming or conventional hydroponics whilst also closing the

food-water-energy cycle within a circular bio-based economy. In order to make

small-scale aquaponics systems economically viable, aquaponics farmers generally

have to operate in niche markets to obtain higher price s for products, so certi ﬁcation

thus becomes very important.

The most pressing issues are whether aquaponics can become acceptable at the

policy level. Food safety is a high priority for gaining public support, and although

there is a much lowered pathogen risk in closed systems, thus implying less need for

antimicrobials and pesticides, managing potential risks – or moreover managing

perceptions of those risks, especially as they may affect food safety – is a high

priority for government authorities and investors alike (Miličić et al. 2017). One

concern that is often raised is the fear of pathogen transfer in sludge from ﬁsh to

plants, but this is not substantiated in the literature (Chap. 6). As such, there is a need

to allay any remaining food safety and biose curity concerns through careful research

and, where concerns may exist, to ascertain how it may be possible to manage these

problems through improved system designs and/or regulatory frameworks.

Aquaponics is an emerging food production technology which has the ability to

condense and compress production into spaces and places that would not normally

be used for growing food. This not only means that it is exceptionally relevant in

urban areas, where aquaponics can be placed on underutilized and unused places

such as ﬂat roofs, development sites, abandoned factories, housing estates and

schools, but it provides a means both in the developed and developing world for

people to take back part of the food production process by providing fresh local food

to the market (van Gorcum et al. 2019). The integration of aquaponics with vertical

farming and living wall technologies will, in time, most likely improve productivity

by reducing the overall farming footprint with reduced land take and intensiﬁcation.

The intense production methods in aquaponics rely on the knowledge of a

combination of key factors which are highly suitable for use in teaching STEM

(science, technology, enginee ring and maths) subjects in schools. Aquaponics pro-

vides the teacher and student with opportunities to explore the realm of complex

systems, their design and management and a host of other subject areas, including

environmental sciences, water chemistry, biology and animal welfare. Aquapon ics is

also being used in prisons/correctional facilities, such as at the San Francisco County

Jail, to help inmates gain skills and experience in aquaculture and horticulture that

they can use on their release. In the domestic context, there is a growing trend to

design countertop systems that can grow herbs as well as small systems that can be

located in ofﬁces, where exotic ﬁsh provide a calming effect, whilst plant s, as part of

living walls, similarly provid e an aesthetic backdrop and clean the air.

Aquaponics is a farming technology advancing rapidly from its ﬁrst exploits in

the last years of the twentieth century and the ﬁrst decades of the twenty-ﬁrst

century. But it still is an ‘emerging technology and science topic’ (Junge et al.

2017) which is subject to a considerable amount of ‘hype’. When comparing the

number of aquaculture, hydroponic and aquaponic peer-reviewed papers, aquaponic

1 Aquaponics and Global Food Challenges 13

papers are considerably lower (Fig. 1.3), but the numbers are rising and will continue

to rise as aquaponics education, especially at university level, and general interest

increases. A ‘hype ratio’ can be described as an indicator of the popularity of a

subject in the public media relative to what is published in the academic press. This

can, for example, be calculated by taking the search results in Google divided by the

search results in Google Scholar. In the case of aquaponics, the hype ratio on

16 August 2016 was 1349, which is considerable when compared to the hype ratios

of hydroponics (131) and recirculating aquacul ture (17) (Junge et al. 2017). The

sense one gets from this is that, indeed, aquaponics is an emerging technology but

that there is enormous interest in the ﬁeld which is likely to continue and increase

over the next decades. The hype ratio, however, is likely to decline as more research

is undertaken and scientiﬁc papers are published.

This book is aimed at the aquaponics researcher and practitioner, and it ha s been

designed to discuss, explore and reveal the issues that aquaponics is addressing now

and that will no doubt arise in the future. With such a broad spectrum of topics, it

aims to provide a comprehensive but easily accessible overview of the rather novel

scientiﬁc and commercial ﬁeld of aquaponics. Apart from the production and

technical side, this book has been designed to address trends in food supply and

demand, as well as the various economic, environmental and social implications of

this emerging technology. The book has been co-authored by numerous experts from

around the world, but mostly from within the EU. Its 24 chapters cov er the whole

gamut of aquaponics areas and will provide a necessary textbook for all those

interested in aquaponics and moving aquaponics forwards into the next decade.

Numbers of Publications

(Hydroponics & Aquaponics)

RAS

Hydroponics

Aquaponics

1980 20181990 2000 2010

Numbers of Publications

(RAS)

9000

8000

7000

6000

5000

4000

3000

2000

1000

900

800

700

600

500

400

300

200

100

Fig. 1.3 The number of papers published on ‘hydroponics’, ‘RAS ’ and ‘aquaponics’ from 1980 to

2018 (data were collected from the Scopus database on 30 January 2019). Please note that the scale

for ‘RAS’ is one order of magnitude higher than that for ‘hydroponics’ and ‘aquaponics’

14 S. Goddek et al.

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1 Aquaponics and Global Food Challenges 17

Chapter 2

Aquaponics: Closing the Cycle on Limited

Water, Land and Nutrient Resources

Alyssa Joyce, Simon Goddek, Benz Kotzen, and Sven Wuertz

Abstract Hydroponics initially developed in arid regions in response to freshwater

shortages, while in areas with poor soil, it was viewed as an opportunity to increase

productivity with fewer fertilizer inputs. In the 1950s, recirculating aquaculture also

emerged in response to similar water limitations in arid regions in order to make

better use of available water resources and better contain wastes. However, disposal

of sludge from such systems remained problematic, thus leading to the advent of

aquaponics, wherein the recycling of nutrients produced by ﬁsh as fertilizer for

plants proved to be an innovative solution to waste discharge that also had economic

advantages by producing a second marketable product. Aquaponics was also shown

to be an adapta ble and cost-effective technology given that farms could be situated in

areas that are otherwise unsuitable for agriculture, for instance, on rooftops and on

unused, derelict factory sites. A wide range of cost savings could be achieved

through strategic placement of aquaponics sites to reduce land acquisition costs,

and by also allowing farming closer to suburban and urban areas, thus reducing

transportation costs to markets and hence also the fossil fuel and CO

footprints of

production.

Keywords Aqua ponics · Sustainable agriculture · Eutrophication · Soil

degradation · Nutrient cycling

A. Joyce (*)

Department of Marine Science, University of Gothenburg, Gothenburg, Sweden

e-mail: alyssa.joyce@gu.se

S. Goddek

Mathematical and Statistical Methods (Biometris), Wageningen University, Wageningen,

The Netherlands

e-mail: simon.goddek@wur.nl; simon@goddek.nl

B. Kotzen

School of Design, University of Greenwich, London, UK

e-mail: b.kotzen@greenwich.ac.uk

S. Wuertz

Department Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Biology and

Inland Fisheries, Berlin, Germany

e-mail: wuertz@igb-berlin.de

S. Goddek et al. (eds.), Aquaponics Food Production Systems,

https://doi.org/10.1007/978-3-030-15943-6_2

2.1 Introduction

The term ‘tipping point’ is currently being used to describe natural systems that are

on the brink of signiﬁcant and potentially catastrophic change (Barnosky et al.

2012). Agricultural food production systems are consi dered one of the key ecolog-

ical services that are approaching a tipping point, as climate change increasingly

generates new pest and disease risks, extreme weather phenomena and higher global

temperatures. Poor land management and soil conservation practices, depletion of

soil nutrients and risk of pandemics also threaten world food supplies.

Available arable land for agricultural expansion is limited, and increased agricul-

tural productivity in the past few decades has primarily resul ted from increased

cropping intensity and better crop yiel ds as opposed to expansion of the agricultural

landmass (e.g. 90% of gains in crop production have been a result of increased

productivity, but only 10% due to land expansion) (Alexandratos and Bruinsma

2012; Schmidhuber 2010). Global population is estimated to reach 8.3–10.9 billion

people by 2050 (Bringezu et al. 2014), and this growing world population, with a

corresponding increase in total as well as per capita consumption, poses a wide range

of new societal challenges. The United Nations Convention to Combat Desertiﬁca-

tion (UNCCD) Global Land Outlook Working Paper 2017 report notes worrying

trends affecting food production (Thoma s et al. 2017) including land degradation,

loss of biodiversity and ecosystems, and decreased resilience in response to envi-

ronmental stresses, as well as a widening gulf between food production and demand.

The uneven distribution of food supplies results in inadequate quantities of food, or

lack of food of sufﬁcient nutritional quality for part of the global population, while in

other parts of the world overconsumption and diseases related to obesity have

become increasingly common. This unbalanced juxtaposition of hunger and malnu-

trition in some parts of the world, with food waste and overconsumption in others,

reﬂects complex interrel ated factors that include political will, resource scarcity, land

affordability, costs of energy and fertilizer, transportation infrastructure and a host of

other socioeconomic factors affecting food production and distribution.

Recent re-examinations of approaches to food security have determined that a

‘water-energy-food nexus’ approach is required to effectively understand, analyse

and manage interactions among global resource systems (Scott et al. 2015). The

nexus approach acknowledges the interrelatedness of the resource base – land, water,

energy, capital and labour – with its drivers, and encourages inter-sectoral consul-

tations and collaborations in order to balance different resource user goals and

interests. It aims to maximize overall beneﬁts while maintaining ecosystem integrity

in order to achieve food security. Sustainable food production thus requires reduced

utilization of resources, in particular, water, land and fossil fuels that are limited,

costly and often poorly distributed in relation to population growth, as well as

recycling of existing resources such as water and nutrients wi thin production

systems to minimize waste.

20 A. Joyce et al.

In this chapter, we discuss a range of current challeng es in relation to food

security, focusing on resource limitations and ways that new technologies and

interdisciplinary approaches such as aquaponics can help address the water-food-

energy nexus in relation to the UN’s goals for sustainable development. We con-

centrate on the need for increased nutrient recycling, reductions in water consump-

tion and non-renewable energy, as well as increased food production on land that is

marginal or unsuitable for agriculture.

2.2 Food Supply and Demand

2.2.1 Predictions

Over the last 50 years, total food supply has increased almost threefold, whereas the

world’s population has only increased twofold, a shift that has been accompanied by

signiﬁcant changes in diet related to economic prosperity (Keatin g et al. 2014). Over

the last 25 years, the world’s population increased by 90% and is expected to reach

the 7.6 billion mark in the ﬁrst half of 2018 (Worldometers). Estimates of increased

world food demand in 2050 relative to 2010 vary between 45% and 71% depending

on assumptions around biofuels and waste, but clearly there is a production gap that

needs to be ﬁlled. In order to avoid a reversal in recent downward trends under-

nourishment, there must be reductions in food demand and/or fewer losses in food

production capacity (Keating et al. 2014). An increasingly important reason for

rising food demand is per capita consumption, as a result of rising per capita income,

which is marked by shifts towards high protein foods, particularly meat (Ehrlich and

Harte 2015b). This trend creates further pressures on the food supply chain, since

animal-based production systems generally require disproportionately more

resources, both in water consumption and feed inputs (Rask and Rask 2011; Ridoutt

et al. 2012; Xue and Lan dis 2010). Even though the rate of increasing food demand

has declined in recent decades, if current trajectories in population growth and

dietary shifts are realistic, global demand for agricultural products will grow at

1.1–1.5% per year until 2050 (Alexandratos and Bruinsma 2012).

Population growth in urban areas has put pressure on land that has been tradi-

tionally used for soil-based crops: demands for housing and amenities continue to

encroach on prime agricultural land and raise its value well beyond what farmers

could make from cultivation. Close to 54% of the world’s population now lives in

urban areas (Esch et al. 2017), and the trend towards urbanization show s no signs of

abating. Production systems that can reliably supply fresh foods close to urban

centres are in demand and will increase as urbanization increases. For instance, the

rise of vertical farming in urban centres such as Singapore, where land is at a

premium, provides a strong hint that concent rated, highly productive farming sys-

tems will be an integral part of urban development in the future. Technological

advances are increasingly making indoor farming systems economical, for instance

the development of LED horticultural lights that are extremely long lasting and

2 Aquaponics: Closing the Cycle on Limited Water, Land and Nutrient Resources 21

energy efﬁcient has increased competitiveness of indoor farming as well as produc-

tion in high latitudes.

Analysis of agrobiodiversity consistently shows that high- and middle-income

countries obtain diverse foods through national or internati onal trade, but this also

implies that production and food diversity are uncoupled and thus more vulnerable to

interruptions in supply lines than in low-income countries where the majority of food

is produced nationally or regionally (Herrero et al. 2017). Also, as farm sizes

increase, crop diversity, especially for crops belonging to highly nutritious food

groups (vegetables, fruits, meat), tends to decrease in favour of cereals and legumes,

which again risks limiting local and regional availability of a range of different food

groups (Herrero et al. 2017).

2.3 Arable Land and Nutrients

2.3.1 Predictions

Even as more food needs to be produced, usable land for agricultural practices is

inherently limited to roughly 20–30% of the world ’s land surface. The availability of

agricultural land is decreasing, and there is a shortage of suitable land where it is

most needed, i.e. particularly near population centres. Soil degradation is a major

contributor to this decline and can generally be categorized in two ways: displace-

ment (wind and water erosion) and internal soil chemical and physical deterioration

(loss of nutrients and/or organic matter, salinization, acidi ﬁcation, pollution, com-

paction and waterlo gging). Estimating total natural and human-induced soil degra-

dation worldwide is fraught with difﬁculty given the variability in deﬁnitions,

severity, timing, soil categorization, etc. However, it is generally agreed that its

consequences have resulted in the loss of net primary production over large areas

(Esch et al. 2017), thus restricting increases in arable and permanently cropped land

to 13% in the four decades from the early 1960s to late 1990s (Bruinsma 2003).

More importantly in relation to population growth during that time period, arable

land per capita declined by about 40% (Conforti 2011). The term ‘arable land’

implies availability of adequate nutrients to support crop production. To counteract

nutrient depletion, worldwide fertilizer consumption has risen from 90 kg/ha in 2002

to 135 kg in 2013 (Pocketbook 2015). Yet the increased use of fertilizers often

results in excesses of nitrate and phosphates ending up in aquatic ecosystems

(Bennett et al. 2001), causing algal blooms and eutrophication when decaying

algal biomass consumes oxygen and limits the biodiversity of aquatic life. Large-

scale nitrate and phosphate-induced environmental changes are particularly evident

in watersheds and coastal zones.

Nitrogen, potassium and phosphorus are the three major nutrients essential for

plant growth. Even though demand for phosphorus fertilizers continues to grow

22 A. Joyce et al.

exponentially, rock phosphate reserves are limited and estimates suggest they will be

depleted within 50–100 years (Cordell et al. 2011; Steen 1998; Van Vuuren et al.

2010). Additionally, anthropogenic nitrogen input is expected to drive terrestrial

ecosystems towards greater phospho rous limitations, although a better understand-

ing of the processes is critical (Deng et al. 2017; Goll et al. 2012; Zhu et al. 2016).

Currently, there are no substitutes for phosphorus in agriculture, thus putting con-

straints on future agricultural productivity that relies on key fertilizer input of mined

phosphate (Sverdrup and Ragnarsdottir 2011). The ‘P-paradox’, in other words, an

excess of P impairing water quality, alongside its shortage as a depleting

non-renewable resource, means that there must be substantial increases in recycling

and efﬁciency of its use (Leinweber et al. 2018).

Modern intensive agricultural practices, such as the frequency and timing of

tillage or no-till, application of herbicides and pesticides, and infrequent addition

of organic matter containing micronutrients can alter soil structure and its microbial

biodiversity such that the addition of fertilizers no longer increases productivity per

hectare. Given that changes in land usage have resulted in losses of soil organic

carbon estimated to be around 8%, and projected losses between 2010 and 2050 are

3.5 times that ﬁgure, it is assumed that soil water-holding capacity and nutrient

losses will continue, especially in view of global war ming (Esch et al. 2017).

Obviously there are trade-offs between satisfying human needs and not compromis-

ing the ability of the biosph ere to support life (Foley et al. 2005). However, it is

clear when modelling planetary boundaries in relation to current land use prac-

tices that it is necessary to improve N and P cycling, principally by reducing both

nitrogen and phosphorus emissions and runoff from agricultural land, but also by

better capture and reuse (Conijn et al. 2018).

2.3.2 Aquaponics and Nutrients

One of the principal beneﬁts of aquaponics is that it allows for the recycling of

nutrient resources. Nutrient input into the ﬁsh component derives from feed, the

composition of which depends on the target species, but feed in aquaculture typically

constitutes a signiﬁcant portion of input costs and can be more than half the total

annual cost of production. In certain aquaponi cs designs, bacterial biomass can also

be harnessed as feed, for instan ce, where bioﬂoc production makes aquaponic

systems increasingly self-contained (Pinho et al. 2017).

Wastewater from open-cage pens or raceways is often discharged into

waterbodies, where it results in nutrient pollution and subsequent eutrophication.

By contrast, aquaponic systems take the dissolved nutrients from uneaten ﬁsh feed

and faeces, and utilizing microbes that can break down organic matter, convert the

nitrogen and phosphorous into bioavailable forms for use by plants in the hydro-

ponics unit. In order to achieve economically acceptable plant production levels, the

2 Aquaponics: Closing the Cycle on Limited Water, Land and Nutrient Resources 23

presence of appropriate microbial assemblages reduces the need to add much of the

supplemental nutrients that are routinely used in stand-alone hydroponic units. Thus

aquaponics is a near-zero discharge system that offers not only economic beneﬁt

from both ﬁsh and plant production streams, but also signiﬁcant reductions in both

environmentally noxious discharges from aquaculture sites. It also eliminates the

problem of N- and P-rich runoff from fertilizers used in soil-based agriculture. In

decoupled aquaponic systems, aerobic or anaerobic bioreactors can also used to treat

sludge and recover signiﬁcant macro- and micronutrients in bioavailable forms for

subsequent use in hydroponic production (Goddek et al. 2018) (see Chap. 8).

Exciting new developments such as these, many of which are now being realized for

commercial prodution, continue to reﬁne the circular economy concept by increas-

ingly allowing for nutrient recovery.

2.4 Pest, Weed and Disease Control

2.4.1 Predictions

It is generally recognized that control of diseases, pests and weed s is a critical

component of curbing production losses that threaten food security (Keating et al.

2014). In fact, increasing the use of antibiotics, insecticides, herbicides and fungi-

cides to cut losses and enhance productivity has allowed dramatic increases in

agricultural output in the latter half of the twentieth century. However, these

practices are also linked to a host of problems: pollution from persistent organic

compounds in soils and irrigation water, changes in rhizobacterial and mycorrhizal

activity in soil s, contamination of crops and livestock, development of resistant

strains, detrimental effects on pollinators and a wide range of human health risks

(Bringezu et al. 2014; Ehrlich and Harte 2015a; Esch et al. 2017; FAO 2015b).

Tackling pest, weed and disease control in ways that reduce the use of these

substances is mentioned in virtually every call to provide food security for a growing

world population.

2.4.2 Control of Pests, Weeds and Diseases

As a closed system with biosecurity measures, aquaponic systems require far fewer

chemical pesticide applications in the plant component. If seed and transplant stocks

are carefully handled and monitored, weed, fungal and bacterial/algal contaminants

can be controlled in hydroponic units with targeted measures rather than the wide-

spread preventive application of herbicides and fungicides prevalent in soil-based

agriculture. As technology continues to advance, developments such as positive

pressure greenhouses can further reduce pest problems (Mears and Both 2001).

Design features to reduce pest risks can cut costs in terms of chemicals, labour,

24 A. Joyce et al.

application time and equipment, especially since the land footprint of industrial-scale

aquaponics systems is small, and systems are compact and tightly contained, as

compared to the equivalent open production area of vegetable and fruit crops of

conventional soil-based farms.

The use of RAS in aquaponic systems also prevents disease transmissions

between farmed stocks and wi ld populations, which is a press ing concern in ﬂow-

through and open-net pen aquaculture (Read et al. 2001; Samuel-Fitwi et al. 2012).

Routine antibiotic use is generally not requi red in the RAS component, since it is a

closed system with few avail able vectors for disease introduction. Furthermore, the

use of antimicrobials and antiparasitics is generally discouraged, as it can be

detrimental to the microbiota that are crucial for converting organic and inorganic

wastes into usable compounds for plant growth in the hydroponic unit (Junge et al.

2017). If disease does emerge, containment of both ﬁsh and plants from the

surrounding environment makes decontamination and eradication more manageable.

Although closed systems clearly do not completely alleviate all disease and pest

problems (Goddek et al. 2015), proper biocontrol measures that are already practised

in stand-alone RAS and hydroponics result in signiﬁcant reductions of risk. These

issues are discussed in further detail in subsequent chapters (for ﬁsh, see Chap. 6; for

plants, further details in Chap. 14).

2.5 Water Resources

2.5.1 Predictions

In addition to requiring fertilizer applications, modern inte nsive agricultural prac-

tices also place high demands on water resources. Among bioche mical ﬂows

(Fig. 2.1), water scarcity is now beli eved to be one of the most important factors

constraining food product ion (Hoekstra et al. 2012; Porkka et al. 2016). Projected

global population increases and shifts in terrestrial water availability due to climate

change, demand more efﬁcient use of water in agriculture. As noted previously, by

2050, aggregate agriculture production will need to produce 60% more food globally

(Alexandratos and Bruinsma 2012), with an estimated 100% more in developing

countries, based on population growth and rising expectations for standards of living

(Alexandratos and Bruinsma 2012;WHO2015). Famine in some regio ns of the

world, as well as malnutrition and hidden hunger, indicates that the balance between

food demand and availability has already reached critical levels, and that food and

water security are directly linked (McNeill et al. 2017). Clim ate change predictions

suggest reduced freshwater availability, and a corresponding decrease in agricultural

yields by the end of the twenty-ﬁrst century (Misra 2014).

The agriculture sector currently accounts for roughly 70% of the freshwater use

worldwide, and the withdrawal rate even exceeds 90% in most of the world’s least-

developed countries. Water scarcity will increase in the next 25 years due to

expected population growth (Connor et al. 2017; Esch et al. 2017), with the latest

2 Aquaponics: Closing the Cycle on Limited Water, Land and Nutrient Resources 25

modelling forecasting declining water availability in the near future for nearly all

countries (Distefano and Kelly 2017). The UN predicts that the pursuit of business-

as-usual practices will result in a global water deﬁcit of 40% by 2030 (Water 2015).

In this respect, as groundwater supplies for irrigation are depleted or contaminated,

and arid regions experience more drought and water shortages due to climate change,

water for agricultural production will become increasingly valuable (Ehrlich and

Harte 2015a). Increasing scarcity of water resources compromises not only water

security for human consumption but also global food production (McNeill et al.

2017). Given that wat er scarcity is expected even in areas that currently have

relatively sufﬁcient water resources, it is important to develop agricultural tech-

niques with low water input requirements, and to improve ecological management of

wastewater through better reuse (FAO 2015a).

The UN World Water Development Report for 2017 (Connor et al. 2017) focuses

on wastewater as an untapped source of energy, nutrients and other useful

by-products, with implications not only for human and environmental health but

also for food and energy security as well as climate change mitigation. This report

calls for appropriate and affordable technologies, along with legal and regulatory

frameworks, ﬁnancing mechanisms and increased social acceptability of wastewater

treatment, with the goal of achieving water reuse within a circular economy. The

report also points to a 2016 World Economic Forum report that lists the water crisis

as the global risk of highest concern in the next 10 years.

Water Foodprint (litres of water per 1 kg)

Beef15.500

Pork4.800

Chicken 3.900 Fish (RAS)400

Cricket 4.300

One Drop (shown in the illustration)

is equivalent to 500 litres of water.

Fig. 2.1 Water footprint

(L per kg). Fish in RAS

systems use the least water

of any food production

system

26 A. Joyce et al.

The concept of a water footprint as a measure of humans’ use of freshwater

resources has been put forwards in order to inform policy development on water use.

A water footprint has three components: (1) blue water, which comprises the surface

and groundwater consumed while making products or lost through evaporation,

(2) green water that is rainwater used especially in crop production and (3) grey

water, which is water that is polluted but still wi thin existing water quality standards

(Hoekstra and Mekonnen 2012). These authors mapped water footprints of countries

worldwide and found that agricultural production accounts for 92% of global

freshwater use, and industrial production uses 4.4% of the total, while domestic

water only 3.6%. This raises concerns about water availability and has resulted in

public education efforts aimed at raising awareness about the amounts of water

required to produce various types of food, as well as national vulnerabilities,

especially in water-scarce countries in North Africa and the Middle East.

2.5.2 Aquaponics and Water Conservation

The economic concept of comparative productivity measures the relative amount of

a resource needed to produce a unit of goods or services. Efﬁciency is generally

construed to be higher when the requirement for resource input is lower per unit of

goods and services. However, when water-use ef ﬁciency is exami ned in an envi-

ronmental context, water quality also needs to be taken into account, because

maintaining or enhancing water quality also enhances productivity (Hamdy 2007).

The growing problem of water scarcity demands improvements in water-use

efﬁciencies especially in arid and semiarid regions, where availability of water for

agriculture, and water quality of discharge, are critical factors in food production. In

these regions, recirculation of water in aquaponic units can achieve remarkable

water re-use efﬁciency of 95–99% (Dalsgaard et al. 2013). Water demand is also less

than 100 L/kg of ﬁsh harvested, and water quality is maintained within the system

for production of crops (Goddek et al. 2015). Obviousl y, such systems must be

constructed and operated to min imize water losses; they must also optimize their

ratios of ﬁsh water to plants, as this ratio is very important in maximizing water re-

use efﬁciency and ensuring maximal nutrient recycling. Modelling algorithms and

technical solutions are being developed to integrate improvements in individual

units, and to better understand how to effectively and efﬁciently manag e water

(Vilbergsson et al. 2016). Further information is provided in Chaps. 9 and 11.

In light of soil, water and nutrient requirements, the water footprint of aquaponic

systems is considerably better than traditional agriculture, where water quality and

demand, along with availability of arable land, costs of fertilizers and irrigation are

all constraints to expansion (Fig. 2.1).

2 Aquaponics: Closing the Cycle on Limited Water, Land and Nutrient Resources 27

2.6 Land Utilization

2.6.1 Predictions

Globally, land-based crops and pasture occupy approximately 33% of total available

land, and expansion for agricultural uses between 2000 and 2050 is estimated to

increase by 7–31% (350–1500 Mha, depending on source and underlying assump-

tions), most often at the expense of forests and wetlands (B ringezu et al. 2014 ).

While there is currently still land classed as ‘good’ or ‘marginal’ that is available for

rain-fed agriculture, signiﬁcant portions of it are far from markets, lack infrastructure

or have endem ic diseases, unsuitable terrain or other conditions that limit develop-

ment potential. In other cases, remaining lands are already protected, forested or

developed for other uses (Alexandratos and Bruinsma 2012). By contrast, dryland

ecosystems, deﬁned in the UN’ s Commission on Sustainable Development as arid,

semiarid and dry subhumid areas that typically have low productivity, are threatened

by desertiﬁcation and are therefore unsuitable for agricultural expansion but never-

theless have many millions of people living in close proximity (Economic 2007).

These facts point to the need for more sustainable intensiﬁcation of food production

kg feed / kg edible weightkg feed / kg liveweight

Percentage of

animal edible

Efficiencies of Production

of Conventional Meat, Fish and Crickets

Beef

Pork

ChickenFish

(Cat fish)

Cricket

4055555580

Fig. 2.2 Feed conversion ratios (FCRs) based as kg of feed per live weight and kg of feed for edible

portion. Only insects, which are eaten whole in som e parts of the world, have a better FCR than ﬁsh

28 A. Joyce et al.

closer to markets, preferably on largely unproductive lands that may never become

suitable for soil-based farming.

The two most important factors contributing to agricultural input efﬁciencies are

considered by some experts to be (i) the location of food production in areas where

climatic (and soil) conditions naturally increase efﬁciencies and (ii) reductions in

environmental impacts of agricultural production (Michael and David 2017). There

must be increases in the supply of cultivated biomass achieved through the intensi-

ﬁcation of production per hectare, accompanied by a diminished environmental

burden (e.g. degradation of soil structure, nutrient losses, toxic pollution). In other

words, the footprint of efﬁcient food production must shrink while minimizing

negative environmental impacts.

2.6.2 Aquaponics and Land Utilization

Aquaponic production systems are soilless and attempt to recycle essential nutrients

for cultivation of both ﬁsh and plants, thereby using nutrients in organic matter from

ﬁsh feed and wastes to minimize or eliminate the need for plant fertilizers. For

instance, in such systems, using land to mine, process, stockpile and transport

phosphate or potash-rich fertilizers becomes unnecessary, thus aso eliminating the

inherent cost, and cost of application, for these fertilizers.

Aquaponics production contributes not only to water usage efﬁciency (Sect.

2.5.2) but also to agricultural input ef ﬁciency by reducing the land footprint needed

for production. Facilities for instance, can be situated on nonarable land and in

suburban or urban areas closer to markets, thus reducing the carbon footprint

associated with rural farms and transportation of products to city markets. With a

smaller footprint, production capacity can be located in other wise unproductive

areas such as on rooft ops or old factory sites, which can also reduce land acquisition

costs if those areas are deemed unsuitable for housing or retail businesses. A smaller

footprint for production of high-quality protein and vegetables in aquaponics can

also take pressure away from clearing ecologically valuable natural and semi-natural

areas for conventional agriculture.

2.7 Energy Resources

2.7.1 Predictions

As mechanization spreads globally, open-ﬁeld intensive agriculture increasingly

relies heavily on fossil fuels to power farm machinery and for transportation of

fertilizers as well as farm products, as well as to run the equipment for processing,

packaging and storage. In 2010, the OECD International Energy Agency predicted

that global energy consumption would grow by up to 50% by 2035; the FAO has

2 Aquaponics: Closing the Cycle on Limited Water, Land and Nutrient Resources 29

also estimated that 30% of global energy consumption is devoted to food production

and its supply chain (FAO 2011). Greenhouse gas (GHG) emissions associated with

fossil fuels (approximately 14% in lifecycle analysis) added to those from fertilizer

manufacturing (16%) and nitrous oxide from average soils (44%) (Camargo et al.

2013), all contribute substantially to the environmental impacts of farming. A trend

in the twenty-ﬁrst century to produce crop-based biofuels (e.g. corn for ethanol) to

replace fossil fuels has increased pressure on the clearing of rainforest s, peatlands,

savannas and grasslands for agricultural production. However, studies point to

creation of a ‘carbon debt’ from such practices, since the overall release of CO

exceeds the reductions in GHGs they provide by displ acing fossil fuels (Fargione

et al. 2008). Arguably a similar carbon debt exists when clearing land to raise food

crops via conventional agriculture that relies on fossil fuels.

In a comparative analysis of agricultural production systems, trawling ﬁsheries

and recirculating aquaculture systems (RAS) were found to emit GHGs 2–2.5 times

that of non-trawling ﬁsheries and non-RAS (pen, raceway) aquacul ture. In RAS,

these energy requirements relate primarily to the functioning of pumps and ﬁlters

(Michael and David 2017). Similarly, greenhouse production systems can emit up to

three times more GHGs than open-ﬁeld crop production if energy is required to

maintain heat and light within optimal ranges (ibid.). However, these GHG ﬁgures

do not take into account other environmental impacts of non-RAS systems, such as

eutrophication or potent ial pathogen transfers to wild stocks. Nor do they consider

GHG from the production, transportation and application of herbicides and pesti-

cides used in open-ﬁeld cultivation, nor methane and nitrous oxide from associated

livestock production, both of which have a 100-year greenhouse warming potential

(GWP) 25 and 298 times that of CO

, respectively (Camargo et al. 2013; Eggleston

et al. 2006).

These sobering estimates of present and future energy consumption and GHG

emissions associated with food production have prompted new modelling and

approaches, for example, the UN’s water-food-energy nexus approach mentioned

in Sect. 2.1. The UN’s Sustainable Development Goals have pinpointed the vulner-

ability of food product ion to ﬂuctuations in energy prices as a key driver of food

insecurity. This has prompted effor ts to make agrifood systems ‘energy smart’ with

an emphasis on improving energy efﬁciencies, increasing use of renewable energy

sources and encouraging integration of food and energy production (FAO 2011).

2.7.2 Aquaponics and Energy Conservation

Technological advances in aquaponi c system operations are moving towards being

increasingly ‘energy smart’ and reducing the carbon debt from pumps, ﬁlters and

heating/cooling devices by using electricity generated from renewable sources. Even

in temperate latitudes, many new designs allow the energy involved in heating and

cooling of ﬁsh tanks and greenhouses to be fully reintegrated, such that these

systems do not require inputs beyond solar arrays or the electricity/heat generated

30 A. Joyce et al.

from bacterial biogas production of aquaculture-derived sludge (Ezebuiro and

Körner 2017; Goddek and Keesman 2018; Kloas et al. 2015; Yogev et al. 2016).

In addition, aquaponi c systems can use microbial denitriﬁcation to convert nitrous

oxide to nitrogen gas if enough carbon sources from wastes are available, such that

heterotrophic and facultative anaerobic bacteria can convert excess nitrates to

nitrogen gas (Van Rijn et al. 2006). As noted in Sect. 2.7.1, nitrous oxide is a potent

GHG and microbes already present in closed aquaponics systems can facilitate its

conversion into nitrogen gas.

2.8 Summary

As the human population continues to increase, there is increasing demand for high-

quality protein worldwide. Compared to meat sources, ﬁsh are widely recognized as

being a particularly healthy source of protein. In relation to the world food supply,

aquaculture now provides more ﬁsh protein than capture ﬁsheries (FAO 2016).

Globally, human per capita ﬁsh consumption continues to rise at an annual average

rate of 3.2% (1961–2013), which is double the rate of population growth. In the

period from 1974 to 2013, biologically unsustainable ‘overﬁshing’ has increased by

22%. During the same period, the catch from what are deemed to be ‘fully exploited’

ﬁsheries has decreased by 26%. Aquaculture therefore provides the only possible

solution for meeting incre ased market demand. It is now the fastest growing food

sector and therefore an important component of food security (ibid.)

With the global population estimated to reach 8.3–10.9 billion people by 2050

(Bringezu et al. 2014), sustainable development of the aquaculture and agricultural

sectors requires optimization in terms of production efﬁciency, but also reductions in

utilization of limited resources, in particular, water, land and fertilizers. The beneﬁts

of aquaponics relate not just to the efﬁcient uses of land, water and nutrient resources

but also allow for increased integration of smart energy opportunities such as biogas

and solar power. In this regard, aquaponics is a promising technology for producing

both high-quality ﬁsh protein and vegetables in ways that can use substantially less

land, less energy and less water while also minimizing chemical and fertilizer inputs

that are used in conventional food production.

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