Aquaponics – Coupled cycles of fish and plants

It is well known by now that sus­taina­bi­li­ty in agri­cul­tu­re has not always been ide­al in recent deca­des. The­re are obvious pro­blems regar­ding water and land requi­re­ments, which are par­ti­cu­lar­ly evi­dent in coun­tries whe­re resour­ces are alrea­dy scar­ce. The­se pro­blems will pro­bab­ly inten­si­fy in the future facing the gre­at glo­bal chal­len­ges of our time, abo­ve all the cli­ma­te cri­sis and the extinc­tion of spe­ci­es. But how can we coun­ter­act this and enab­le sus­tainab­le agri­cul­tu­re? One inno­va­ti­ve approach is Aqua­po­nics. For some years now, it has been attrac­ting an incre­a­sing glo­bal inte­rest from pri­va­te indi­vi­du­als, sci­en­tists and entre­pre­neurs and is seen as one of the most attrac­ti­ve alter­na­ti­ves for rea­li­zing the agri­cul­tu­re of tomor­row. In the fol­lowing, we will exp­lain Aquq­po­nics in more detail and how such sys­tems are constructed.

What is Aquaponics?

Aqua­po­nics is a novel and sus­tainab­le method of food pro­duc­tion and is essen­ti­al­ly the com­bi­na­ti­on of two pro­ven agri­cul­tu­ral methods: aquacul­tu­re, the rai­sing of aqua­tic orga­nisms, and hydro­po­nics, the soil­less pro­duc­tion of plants using an aque­ous nut­ri­ent solu­ti­on. The term its­elf is a port­man­te­au, com­po­sed of the names of the two methods (aqua­po­nics = aquacul­tu­re + hydroponics).

Aqua­po­nics sol­ves exis­ting sus­taina­bi­li­ty pro­blems of the indi­vi­du­al sys­tems by com­bi­ning two food pro­duc­tion pro­ces­ses. In the case of fish far­ming, the excre­ta of the ani­mals, which are rich in plant nut­ri­ents, often enter the envi­ron­ment (e. g. in the case of net cages in the sea) and lead to over­fer­ti­liz­a­ti­on the­re. In the case of plant far­ming, the­re is a depen­dence on mine­ral fer­ti­li­zers, which the plants need for an opti­mal growth. Aqua­po­nics feeds the was­te­wa­ter from fish far­ming to the plants for irri­ga­ti­on, so that the plants can use the excre­ta of the ani­mals as fer­ti­li­zer and no super­fluous or unused nut­ri­ents are released into the envi­ron­ment. The plants can absorb the nut­ri­ents very effi­ci­ent­ly and without much ener­gy input, as they are alrea­dy dissolved.

The structure of an Aquaponics system

Aqua­po­nics sys­tems can be imple­men­ted qui­te easi­ly in princip­le, as both methods use water as the cen­tral medi­um. Exis­ting com­pon­ents and parts of aquacul­tu­re tech­no­lo­gy can be used to a lar­ge extent.

At the begin­ning of an aqua­po­nics sys­tem is a fish tank. This is aera­ted so that the ani­mals have oxy­gen to brea­the. The ani­mals eat fish food and excre­te it. The fish’s excre­ment, along with other was­te mate­ri­als such as uri­ne and food resi­du­es, enters the water and is direc­ted into the bio­fil­ter. This con­verts the uri­ne of the ani­mals (ammonium/ammonia) into nitra­te. Sub­se­quent­ly, part of the water is pas­sed through the skim­mer, which remo­ves bac­te­ria and par­ti­cles from the water. Ano­t­her por­ti­on flows into a plant tank whe­re it reaches the roots. In some sys­tems the plants sit in a non-floa­ting sub­stra­te (e. g. expan­ded clay or gra­vel) and are wate­red via drip val­ves, in other sys­tems the plants sit in per­fo­ra­ted tubes and the roots are con­ti­nuous­ly flus­hed with the water.

Struc­tu­re of the SEAWATER aqua­po­nics com­pact system

The assem­bly of an Aqua­po­nics sys­tem can be mas­te­red by prac­ti­cal­ly incli­ned hob­by gar­de­ners or ang­lers them­sel­ves, if necessa­ry. When it comes to ope­ra­ti­on, howe­ver, a deeper under­stan­ding of the bio­lo­gi­cal pro­ces­ses is necessa­ry. For examp­le, the nut­ri­ent flows that take place in such a sys­tem must be cal­cu­la­ted very pre­cise­ly to pro­vi­de opti­mal growth con­di­ti­ons for the plants and the fish. Here, depen­ding on the fish spe­ci­es, appro­pria­te exper­ti­se should be cal­led upon.

Advantages of closed circuits

Aqua­po­nics com­bi­nes many advan­ta­ges and thus can shape future agri­cul­tu­re in a sus­tainab­le way. Such sys­tems are:

✓  Zero­was­te: They help peop­le think in terms of clo­sed cycles and encou­ra­ge them to find solu­ti­ons for resi­du­al mate­ri­als from food production.

✓  Resour­ce-effi­ci­ent: Water is also used very spa­rin­gly; apart from eva­po­ra­ti­on or plant upt­a­ke, no water is lost in clo­sed sys­tems. On the con­tra­ry, it is always puri­fied and circulated.

✓  Envi­ron­ment­al­ly friend­ly: Eutro­phi­ca­ti­on of the soil (= over­fer­ti­liz­a­ti­on) is also avoided, as the plants uti­li­ze nitra­te and phos­pho­rus, and this does not enter the ground­wa­ter via the wastewater.

✓  Emis­si­on-free: The CO2 exha­led by the fish is con­ver­ted to oxy­gen by the plants.

✓  Anti­bio­tic-free: In princip­le, fish farms should always be desi­gned and ope­ra­ted so that the fish grow up in opti­mal con­di­ti­ons and do not beco­me sick. Howe­ver, by inte­gra­ting bio­fil­ters and plants, the use of anti­bio­tics is avoided altog­e­ther, as the­se would other­wi­se harm the bac­te­ria or vege­ta­bles and inhi­bit their growth.

What are the types of Aquaponics?

The type of aqua­po­nics known so far is alrea­dy being imple­men­ted in iso­la­ted lar­ge-sca­le pro­jects and takes place in freshwa­ter. Popu­lar fish spe­ci­es for this are zan­der, cat­fi­sh and tila­pia. The vege­ta­bles often grown in this type of aqua­po­nics are let­tuce, tomatoes or herbs. Howe­ver, the­re are also exci­ting new types of aqua­po­nics alrea­dy in deve­lo­p­ment. The­se inclu­de sys­tems that use sal­ty water (salt­wa­ter aqua­po­nics – mara­po­nics, bra­ckish water aqua­po­nics – halo­po­nics) or sys­tems that invol­ve worms (ver­mi­po­nics) or algae (alge­apo­nics).

We have also been invol­ved in rese­arch into the cou­pling of fish and plant far­ming for a num­ber of years. Howe­ver, we are one of the first groups in Ger­ma­ny to work in salt­wa­ter. We see enor­mous poten­ti­al in this area: on the one hand by pro­du­cing attrac­ti­ve vege­ta­ble plants (such as sea aspa­ra­gus) or algae, and on the other hand by impro­ving the eco­lo­gi­cal foot­print of fish far­ming in land-based facilities.

As part of the IBA Future Lab at htw saar, we have alrea­dy set up a first demons­tra­tor of our aqua­po­nics tech­no­lo­gy. The sys­tem was pre­sen­ted in sum­mer 2021 wit­hin a par­ti­ci­pa­to­ry future lab (FUTURE LAB) at the World Cul­tu­ral Heri­ta­ge Site Völk­lin­ger Hüt­te. and shows what modern food sup­ply can look like.

 

​„The IBA32 pro­ject shows pos­si­bi­li­ties for future sup­ply in urban are­as. The SEAWATER cycle, a modern tech­no­lo­gy for the regio­nal pro­duc­tion of fresh fish, is a per­fect fit for the­se visi­ons. SEAWATER Cubes shows in the World Heri­ta­ge Site Völk­lin­gen with its com­pact aqua­po­nics plant how the inte­gra­ted pro­duc­tion of the future can look like: Nut­ri­ents from the fish pro­duc­tion pro­cess flow into the pro­duc­tion of vege­ta­bles, salads, fruits, simi­lar to natu­ral eco­sys­tems. Aqua­po­nics is THE con­cept for sus­tainab­le nut­ri­ti­on and effi­ci­ent use of valu­able resources.“

 (Prof. Dr. Uwe Wal­ler, men­tor und mari­ne biologist)

How does the future of coupled systems look like?

With the gro­wing popu­la­ti­on and incre­a­sing urba­niz­a­ti­on, the chal­len­ges for a sus­tainab­le food sup­ply are get­ting big­ger. Aqua­po­nics sys­tems are well sui­ted to be set up on a small area, even in cities. The­re, they can sup­ply peop­le in a decen­tra­li­zed man­ner and redu­ce trans­port distan­ces to a mini­mum. Thanks to the low water con­sump­ti­on, the use of land for the instal­la­ti­on of aqua­po­nics is also con­ceiva­ble in rather dry regions.

To date, howe­ver, the­re are no tech­ni­cal­ly auto­ma­ted, pro­duc­tion-rea­dy sys­tems that do litt­le work and can repre­sent an eco­no­mic via­bi­li­ty of both pro­duc­tion units (fish & plant). In pilot pro­jects, it will be necessa­ry in the future to deter­mi­ne exact values for all rele­vant ope­ra­ting para­me­ters and mar­ket pri­ces, as well as to con­duct sales tests in the sales mar­ket with the pro­ducts from lar­ger demons­tra­tors. Con­tai­ners appe­ar to be an exci­ting solu­ti­on for a modern plant farm that ope­ra­tes ver­ti­cal­ly and can be pla­ced next to a con­tai­ne­ri­zed fish farm. Let us see when or with which part­ners we can tack­le this topic on a lar­ger scale.…

Refe­ren­ces:

  • God­dek, Simon, Alys­sa Joy­ce, Sven Wuer­tz, Oli­ver Kör­ner, Ingo Blä­ser, Micha­el Reu­ter, and Karel J. Kees­man. 2019. ‚Deco­u­pled Aqua­po­nics Sys­tems.‘ in Simon God­dek, Alys­sa Joy­ce, Benz Kot­zen and Gavin M. Bur­nell (eds.), Aqua­po­nics Food Pro­duc­tion Sys­tems: Com­bi­ned Aquacul­tu­re and Hydro­po­nic Pro­duc­tion Tech­no­lo­gies for the Future (Sprin­ger Inter­na­tio­nal Publi­shing: Cham).
  • Joy­ce, Alys­sa, Simon God­dek, Benz Kot­zen, and Sven Wuer­tz. 2019. ‚Aqua­po­nics: Clo­sing the Cycle on Limi­ted Water, Land and Nut­ri­ent Resour­ces.‘ in Simon God­dek, Alys­sa Joy­ce, Benz Kot­zen and Gavin M. Bur­nell (eds.), Aqua­po­nics Food Pro­duc­tion Sys­tems: Com­bi­ned Aquacul­tu­re and Hydro­po­nic Pro­duc­tion Tech­no­lo­gies for the Future (Sprin­ger Inter­na­tio­nal Publi­shing: Cham)
  • Len­nard, Wil­son, and Simon God­dek. 2019. ‚Aqua­po­nics: The Basics.‘ in Simon God­dek, Alys­sa Joy­ce, Benz Kot­zen and Gavin M. Bur­nell (eds.), Aqua­po­nics Food Pro­duc­tion Sys­tems: Com­bi­ned Aquacul­tu­re and Hydro­po­nic Pro­duc­tion Tech­no­lo­gies for the Future (Sprin­ger Inter­na­tio­nal Publi­shing: Cham).
  • Mau­cie­ri, Car­me­lo, Car­lo Nico­let­to, Erik van Os, Die­ter Ansee­uw, Robin Van Haver­ma­et, and Ran­ka Jun­ge. 2019. ‚Hydro­po­nic Tech­no­lo­gies.‘ in Simon God­dek, Alys­sa Joy­ce, Benz Kot­zen and Gavin M. Bur­nell (eds.), Aqua­po­nics Food Pro­duc­tion Sys­tems: Com­bi­ned Aquacul­tu­re and Hydro­po­nic Pro­duc­tion Tech­no­lo­gies for the Future (Sprin­ger Inter­na­tio­nal Publi­shing: Cham).
  • https://www.sueddeutsche.de/wirtschaft/bauern-landwirtschaft-nachhaltigkeit‑1.4520651, abge­ru­fen am 20.05.21
  • Pic­tu­re source: SEAWATER Cubes