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Abstract

Nowadays, agriculture must face a new challenge: produce more food with fewer natural resources. To achieve this goal, scientists are testing a technique called aquaponics. Aquaponics was introduced many years ago by ancient Chinese and Mexican populations. In aquaponics, fish and plants are farmed together. How is this possible? Bacteria change the fish poop into nutrients useful for the plants. The plants take up these nutrients and clean the water, which can then be reused to farm the fish, and the cycle restarts! Aquaponics allows farmers to obtain two products at once, and to recycle the same water many times. Almost no wastewater is released into the environment! Aquaponics systems can have different sizes and do not need soil. They can be installed in both outdoor and indoor environments. Big aquaponic systems are used for commercial purposes, while small aquaponic systems can be used for urban farming—growing food within cities.
EARTH AND ITS RESOURCES
Published: 06 April 2022
doi: 10.3389/frym.2022.707801
AQUAPONICS: A PROMISING TOOL FOR
ENVIRONMENTALLY FRIENDLY FARMING
Roberta Calone *and Francesco Orsini
DISTAL—Dipartimento di Scienze e Tecnologie Agro-Alimentari, University of Bologna, Bologna, Italy
YOUNG REVIEWERS:
CHERYL
AGE: 9
PRICE
AGE: 14
PROVIDENCE
AGE: 10
Nowadays, agriculture must face a new challenge: produce more
food with fewer natural resources. To achieve this goal, scientists are
testing a technique called aquaponics. Aquaponics was introduced
many years ago by ancient Chinese and Mexican populations. In
aquaponics, fish and plants are farmed together. How is this possible?
Bacteria change the fish poop into nutrients useful for the plants.
The plants take up these nutrients and clean the water, which can
then be reused to farm the fish, and the cycle restarts! Aquaponics
allows farmers to obtain two products at once, and to recycle the
same water many times. Almost no wastewater is released into the
environment! Aquaponics systems can have dierent sizes and do
not need soil. They can be installed in both outdoor and indoor
environments. Big aquaponic systems are used for commercial
purposes, while small aquaponic systems can be used for urban
farming—growing food within cities.
kids.frontiersin.org April 2022 | Volume 10 |Article 707801 |1
Calone and Orsini Aquaponics: A Promising Tool for Sustainable Farming
Figure 1
Figure 1
Water cycle within an
aquaponics system.
Bacteria convert the
fish poop into nutrients
that are good for the
plants. The plants’ roots
take up these nutrients,
and in doing so,
they clean the water.
The purified water is
reused for fish farming.
In this way, we obtain a
closed water cycle, in
which the same
amount of water
continuously flows.
Water flows from the
fish to the plants, and
then back to the fish,
and so on!
WHAT IS AQUAPONICS?
The population of the world is increasing rapidly, and there is not
enough food to feed this growing population! Scientists have an
important mission: they must find a method for producing more food
without stressing the environment. Traditional farming techniques
damage the environment in many ways. They harm natural resources
and pose health risks to humans and wildlife. A technique called
aquaponics could be a solution to this problem. The “aqua” part of
this word comes from aquaculture, which is the practice of raising
fish, shrimp, algae, and other seafood. The “ponics” part comes from
hydroponics, which is the cultivation of plants in water, without
soil. Aquaculture and hydroponics can exist separately, but when we
combine them, we obtain aquaponics!
Aquaponics is a miniature version of a natural ecosystem. It works the
way Mother Nature normally works in every aquatic environment! First,
in aquaponics, we put the fish to work. By working, we mean eating
and pooping. This results in water that is rich in nutrients—yes, the fish
poop! Then, bacteria come into play. Bacteria convert the fish poop
into a perfect fertilizer for plant growth. The plants take up this fertilizer
with their roots and, in doing so, also clean the water. The clean water
is reused for farming the fish (Figure 1). The cycle restarts!
In an aquaponics system, fish, plants, and bacteria work together as a
team. This teamwork allows farmers to obtain two food products, fish
and vegetables, using the same amount of water that would normally
be used to obtain just one product. In this closed cycle, water is
not wasted—the wastewater released into the environment is almost
zero [1]!
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Calone and Orsini Aquaponics: A Promising Tool for Sustainable Farming
Figure 2
Figure 2
Aquaponics has been
used for about 1,500
years in China, where
rice was grown in
flooded paddy fields
(top). In Mexico, the
Aztecs produced
vegetable on floating
gardens called
chinampas (bottom).
AQUAPONICS, PAST AND PRESENT
The idea of aquaponics is quite old. The first forms of aquaponics were
used about 1,500 years ago, in South China, Indonesia, and Thailand.
The farmers there grew rice in paddy fields that also had fish in them.
PADDY FIELDS
A flooded field used to
grow rice.
The fish poop served as fertilizer for the growth of the rice plants
(Figure 2).
Five hundred years later, a population in central Mexico invented
another form of aquaponics. This population, known as the Aztecs,
created a big empire. The capital of the empire, called Tenochtitlán,
was built on the shores of Lake Texcoco. In that wetland, the Aztecs did
not have fertile lands to cultivate their food. For this reason, they built
gardens floating in the lake, called chinampas. These floating islands
were made of mud and dried plant residue. On the chinampas, farmers
cultivated maize, squash, tomatoes, and other crops. The plants could
take up nutrients from the lake water, which was rich in fish poop.
Although the concept of aquaponics is ancient, it was not until the
1970’s that scientists rediscovered its potential. Nowadays, aquaponics
is becoming quite advanced, and it provides a sustainable solution for
agriculture, that will reduce the use of natural resources. Aquaponics
uses up to 90% less water than traditional agriculture [2] and the plants
grow much faster [3]! Aquaponics also reduces pollutants coming
from the use of tractors and field chemicals [4].
Aquaponics systems can be installed both outdoors and in indoor,
greenhouse-like environments. Indoors systems can allow food to be
produced throughout the year! This is a great advantage in areas where
the climate is not favorable for agriculture, for example, places with
low temperatures, short daylight, and an absence of rain or freshwater
for irrigation.
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Calone and Orsini Aquaponics: A Promising Tool for Sustainable Farming
Figure 3
Figure 3
The three main
aquaponic systems.
Substrate aquaponics
has a soil-like substrate
to help plant growth. In
channel aquaponics,
the plants are placed
within pipes that have
nutrient-rich water
running through them.
In raft aquaponics, the
plants are placed on
floating rafts with their
roots reaching down
into the water for
nutrients. TYPES OF AQUAPONICS
There are three main aquaponics systems in use today (Figure 3).
In raft aquaponics, the plants are grown on floating rafts. The rafts
RAFT AQUAPONICS
System in which plants
are placed in holes
drilled in rafts. The rafts
float within tanks filled
with fish wastewater.
Plant roots dip in the
water where they
absorb nutrients.
float in tanks filled with the wastewater from the fish culture. The
plant roots dip into the water where they can absorb the nutrients
from the fish poop. This method is most appropriate for small plants
like salad greens, basil, spinach, chard, and others. In substrate
aquaponics, the plants grow in a substrate that mimics the soil. This
SUBSTRATE
AQUAPONICS
System in which plants
are placed in holes
drilled within pipes
where continuously the
fish euent water
flows. The roots dip
into the water stream,
where they can uptake
the nutrients.
substrate sustains the plant roots and helps the bacteria to filter the
water. This kind of system is suitable for all types of plants, but it
is most often used for cabbage, broccoli, onions, fennel, carrots,
tomatoes, peppers, cucumbers, beans, peas, squash, and melons. Last,
in channel aquaponics, the wastewater from the fish flows through
CHANNEL
AQUAPONICS
System in which plants
are placed within a
substrate that mimics
the soil. This substrate
also contains bacteria
that help the plant to
uptake nutrients from
the fish wastewater.
narrow pipes with holes, into which the plants are placed. The roots
dip into the stream of water within the pipe, where they can uptake
the nutrients from the fish poop. This growing method works well for
plants that need little support, such as strawberries, leafy greens, and
herbs. The pipes can also be placed vertically to save space.
There are many fish species that can be used in aquaponics systems.
These systems can incorporate large, small, edible, or ornamental fish,
it depends on the ultimate purpose of the system. The most common
species of fish in aquaponics systems are tilapia, bluegill, catfish, carp
koi, fancy goldfish, shrimp, and pacu.
BENEFITS OF AQUAPONICS IN CITIES
Nowadays, there is a growing interest in small-scale aquaponics
systems. These systems can be located within cities; for example,
they can be located in parks, urban gardens, buildings, houses,
courtyards, and on rooftops. Introducing small aquaponics systems
into cities can bring many benefits. Aquaponics can provide
a large variety of organic and seasonal fresh produce. These
vegetables are environmentally friendly because they have a reduced
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Calone and Orsini Aquaponics: A Promising Tool for Sustainable Farming
transport footprint—they do not need to be transported far before
TRANSPORT
FOOTPRINT
Greenhouse gas
emissions from
transportation (trucks,
airplanes,
railways, etc.).
reaching our tables. Urban aquaponics systems can also encourage
social initiatives. For example, they can promote cohousing and
COHOUSING
Communities in which
people have their own
residences but share
common spaces such
as rooftops, courtyards,
and balconies.
educational workshops, both of which provide people with a greater
chance of meeting their neighbors. Aquaponics can also provide a
shelter for birds and beneficial insects, which increases the city’s
biodiversity [5]. Last, urban aquaponics can help to create jobs for
BIODIVERSITY
Set of all living forms
that are on
Earth—plants, animals,
insects, fungi and
micro-organisms, and
their habitats.
people in cities.
In summary, aquaponics is a circular soilless production system. It
allows producing fish and vegetables together with the same amount
of water, helping to save water. By participating in aquaponics, people
can learn more about the lives of plants and fish. They can become
more aware of how the foods they buy in grocery stores have been
produced. This is especially important for younger people in cities and
suburban areas, who are at risk of losing touch with the farming world.
And one more important thing—participating in aquaponics is also a lot
of fun!
ACKNOWLEDGMENTS
The research leading to this publication has received funding from the
European Union’s Horizon 2020 research and innovation programme
under grant agreement No. 862663.
REFERENCES
1. Calone, R., Pennisi, G., Morgenstern, R., Sanyé-Mengual, E., Lorleberg, W.,
Dapprich, P., et al. 2019. Improving water management in European catfish
recirculating aquaculture systems through catfish-lettuce aquaponics. Sci. Tot.
Environ. 687:759–67. doi: 10.1016/j.scitotenv.2019.06.167
2. Graber, A., and Junge, R. 2009. Aquaponic systems: nutrient recycling from fish
wastewater by vegetable production. Desalination 246:147–56. doi: 10.1016/
j.desal.2008.03.048
3. Salam, A., and Prodhan, Y. 2014. Comparative growth performances of taro plant
in aquaponics vs. other systems. Int. J. Innov. Appl. Stud. 7:941–6.
4. Monsees, H., Suhl, J., Paul, M., Kloas, W., Dannehl, D., and Würtz, S. 2019. Lettuce
(Lactuca sativa, variety Salanova) production in decoupled aquaponic systems:
same yield and similar quality as in conventional hydroponic systems but
drastically reduced greenhouse gas emissions by saving inorganic fertilizer. PLoS
ONE 14:e0218368. doi: 10.1371/journal.pone.0218368
5. Orsini, F., Pennisi, G., Michelon, N., Minelli, A., Bazzocchi, G., Sanyé-Mengual, E.,
et al. 2020. Features and functions of multifunctional urban agriculture in the
global north: a review. Front. Sustain. Food Syst. 4:562513. doi: 10.3389/fsufs.
2020.562513
SUBMITTED: 10 May 2021; ACCEPTED: 10 March 2022;
PUBLISHED ONLINE: 06 April 2022.
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Calone and Orsini Aquaponics: A Promising Tool for Sustainable Farming
EDITOR: Suhas Kumar, Hewlett-Packard, United States
SCIENCE MENTOR: Florence Barbara Awino
CITATION: Calone R and Orsini F (2022) Aquaponics: A Promising Tool for
Environmentally Friendly Farming. Front. Young Minds 10:707801. doi: 10.3389/
frym.2022.707801
CONFLICT OF INTEREST: The authors declare that the research was conducted in
the absence of any commercial or financial relationships that could be construed
as a potential conflict of interest.
COPYRIGHT © 2022 Calone and Orsini. This is an open-access article distributed
under the terms of the Creative Commons Attribution License (CC BY). The use,
distribution or reproduction in other forums is permitted, provided the original
author(s) and the copyright owner(s) are credited and that the original publication
in this journal is cited, in accordance with accepted academic practice. No use,
distribution or reproduction is permitted which does not comply with these terms.
YOUNG REVIEWERS
CHERYL, AGE: 9
Hi, I am Cheryl. I have a cat named Delilah and two little sisters called Tanya and Alice.
I live in a small city of Canberra. I am sometimes pretty shy and sometimes pretty
cheeky. I absolutely love icecream especially “Cookies ‘n’ cream.” Love you all.
PRICE, AGE: 14
Price loves making up stories and has also written a book (Ms. Wasteson and the
waste empire). She enjoys gymnastics, athletics, volleyball, and basketball. She is
brave and bouncy. Price also enjoys quality time with family and is very creative.
At her school, she is part of a “green team” that works to protect the environment.
She likes debating and has a passion to study and become an activist against
social injustices.
PROVIDENCE, AGE: 10
Providence is the youngest amongst her three sisters. She is playful and bouncy.
Providence is curious, talkative, and likes asking many funny questions, that leaves
others laughing. She loves making new friends and traveling. Providence loves
science experiments. During this process, she may destroy, repair or recycle some
household items. As part of this adventure, Providence repaired a spoilt speaker. But
after weeks of action, she modeled the speaker wires into skipping ropes. She is
passionate about music and sports including volleyball.
kids.frontiersin.org April 2022 | Volume 10 |Article 707801 |6
Calone and Orsini Aquaponics: A Promising Tool for Sustainable Farming
AUTHORS
ROBERTA CALONE
I believe that we can take inspiration from nature to change the way we produce
food. Most current farming techniques are strongly dependent on natural resources.
Current agriculture needs a lot of land, water, and energy. This is seriously
threatening the environment. Agriculture also produces a lot of pollutants that
pose health risks for humans and animals. My research in aquaponics arises from
the urgent need to improve food-production systems. Aquaponics is an ancient
food-production system, forgotten for many centuries. Aquaponics allows us to
increase agricultural productivity while reducing the use of natural resources. It
is a circular system with almost zero waste. I started my research in Germany,
as a university student and I am now continuing to study this topic for my Ph.D.
at Bologna University. I am also in collaboration with some aquaponic farms in
northern Italy. *roberta.calone3@unibo.it
FRANCESCO ORSINI
I was always intrigued by how a traditional sector like agriculture could accept and
integrate innovation. We always think of farming as a rural activity, even though
most of the world’s population lives in cities, and innovative technologies for
plant cultivation in highly urbanized environments are available. After taking part in
community farming projects in African, South-East Asian and Latin American cities,
I started to perform research on urban agriculture in Italy and Europe. Today I teach
urban agriculture at Bologna University and coordinate research in an EU project
called Food Systems in European Cities (FoodE).
kids.frontiersin.org April 2022 | Volume 10 |Article 707801 |7
Chapter
Full-text available
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Article
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In recent years, urban agriculture (UA) projects have bloomed throughout the world, finding large applications also in the developed economies of the so-called Global North. As compared to projects in developing countries, where research has mainly targeted the contribution to food security, UA in the Global North has a stronger multifunctional connotation, and results in multiple combinations of farming purposes and business models pursued. The present review paper explores the contribution and role that UA plays in cities from the Global North, defining its functionalities toward ecosystem services (ES) provisioning and analyzing the factors that hinders and promote its regional diffusion and uptake. The manuscript integrates a description of UA growing systems, as well opportunities for crop diversification in the urban environment, and a comprehensive classification of UA business models. The distinctive features in terms of business models, farming purposes and farm size are then applied over an inventory of 470 UA projects in the Global North, allowing for a characterization and comparative analysis of distribution frequency of the different project typologies.
Article
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Decoupled aquaponic systems have the potential to become one of the most effective sustainable production systems for the combined production of animal protein and plant crops. Here, recirculating aquaculture systems for fish production are combined with hydroponics for soilless plant production thereby recycling dissolved nutrients derived from metabolism of the fish. The aim of the present study was to characterize hydroponic lettuce production using conventional nutrient solution in comparison with decoupled aquaponics using the nutrient rich fish water as basis for the nutrient solution being supplemented by missing nutrients. In addition, one aquaponic treatment became disinfected in order to assess any occurring advantage of the aquaponics derived fish water. For evaluation the temperature, electrical conductivity, pH, and the mineral composition of the nutrient solution, as well as colony forming units in the fish water were monitored. Additionally, plant growth (fresh and dry weight, number and area of leaves) and quality parameters of lettuce leaves (nitrate, mineral content, phenolic compounds) were examined. Carbon sources and microorganisms derived from fish water seem to have neither beneficial nor detrimental effects on plant growth in this study. Except for some differences in the mineral content of the lettuce leaves, all other quality parameters were not significantly different. The use of aquaponic fish water saved 62.8% mineral fertilizer and fully substituted the required water for the nutrient solution in comparison to the control. Additionally, the reduced fertilizer demand using decoupled aquaponics can contribute to reduce greenhouse gas emissions of an annual lettuce production site per ha by 72% due to saving the energy for fertilizer production. This study clearly demonstrates the huge potential of the innovative approach of decoupled aquaponics to foster the transformation of our conventional agriculture towards sustainable production systems saving resources and minimizing emissions.
Article
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Population pressure and land scarcity hindered the development and food security in Bangladesh. To feed the enormous population, farmers increased crop production using chemical fertilizers, pesticides, herbicides which created environmental pollution and health hazards. Therefore, an experiment was carried out as organic farming to investigate the growth performances of Taro plant (Colocasia esculenta) in aquaponics system (T1), hydroponics with tap water (T2) and in soil (T3). The healthy and equal sized Taro seedlings were used in each method and tilapia was used as experimental fish. Water quality parameters were recorded weekly, fish and vegetable growth was monitored fortnightly and soil quality was measured monthly. Two sample t-test was conducted for morphological parameters and coefficient of variation (CV) was measured for biochemical elements to find out the best performed method. The growth of Taro plant was significantly different in various systems. The highest growth was found in T1 followed by T3 and T2. The mineral contents in the soil were significantly higher than the other systems. Taro plant growth was significantly higher in T1 as waste water continuously supplied nutrients to the plants, hence, the system can be replicated anywhere in the country irrespective of geographic location and weather to overcome the environmental pollution.
Article
In the context of climate change and population growth, aquaculture plays an important role for food security, employment and economic development. Intensive recirculating aquaculture systems (RAS) allow to treat and recycle fish effluents to reduce waste concentration in outflow water thereby reducing environmental contamination. RAS sustainability may be further improved using aquaponics, a circular productive system in which RAS wastewater is recovered for crop cultivation and recycled back to the fish tanks. In this study, water metabolism of a catfish RAS was assessed and the opportunity to produce lettuce with the RAS effluent was tested. Crop growth and water consumption in aquaponics were compared to those experienced in hydroponics at three nutrient solution concentration (EC of 1.6, 2.0 and 3.0 dS∙m−1), also considering water- (WUE) and nitrogen- use efficiency (NUE). A scenario for converting the RAS in a catfish-lettuce aquaponic system was, then, proposed. The RAS water balance included an input of 555 L∙day−1, out of which 32 L∙day−1 were lost by evaporation from the tubs whereas 460 L∙day−1 were discarded. The lettuce yield, NUE and WUE in aquaponics were respectively 20.3%, 22.3% and 20.6% lower than those obtained in hydroponics. Best performances in hydroponics were achieved with EC of 2.0 dS m−1. No difference in term of water consumption arose between the treatments, with average water use of 46 mL∙plant−1∙day−1. Considering the current RAS productivity of 329 kg year−1, a 10 m2 raft system hosting 160 lettuces would satisfy the nitrogen filtration demand. Once closed the water loop between the two productive sub-units, the current water input of 532 L∙day−1 could be reduced to the amount needed to replace the water lost by evaporation (50 L∙day−1) and the RAS water output would decrease from 555 to 103 L∙day−1.
Article
This chapter describes the possibility to combine wastewater treatment in recirculating aquaculture systems (RAS) with the production of crop plants biomass. In an aquaponic RAS established in Waedenswil, Zurich, the potential of three crop plants was assessed to recycle nutrients from fish wastewater. A special design of trickling filters was used to provide nitrification of fish wastewater: Light-expanded clay aggregate (LECA) was filled in a layer of 30 cm in vegetable boxes, providing both surface for biofilm growth and cultivation area for crop plants. Aubergine, tomato and cucumber cultures were established in the LECA filter and nutrient removal rates calculated during 42–105 days. The highest nutrient removal rates by fruit harvest were achieved during tomato culture: over a period of >3 months, fruit production removed 0.52, 0.11 and 0.8 gm−2d−1 for N, P and K in hydroponic and 0.43, 0.07 and 0.4 gm−2d−1 for N, P and K in aquaponic. In aquaponic, 69% of nitrogen removal by the overall system could thus be converted into edible fruits. Plant yield in aquaponic was similar to conventional hydroponic production systems. The experiments showed that nutrient recycling is not a luxury reserved for rural areas with litlle space limitation; instead, the additionally occupied surface generates income by producing marketable goods. By converting nutrients into biomass, treating wastewater could become a profitable business.