Designing aquaponic production systems

Abstract

Samrækt er sjálfbær ræktunaraðferð þar sem fiskur og grænmeti er ræktað saman í lokaðri hringrás næringarefna. Samræktarkerfi samanstendur af fiskitönkum, fastefnasíu, lífhreinsi og vatnsræktarkerfi. Úrgangur fisksins losar næringarefni sem plönturnar nýta sér til vaxtar, við það lækkar styrkur næringarefnanna og kerfið verður vistlegra fyrir fiskinn. Tilgangur rannsóknarinnar var að bera saman ræktun á mismunandi tegundum grænmetis, meta hentugleika íslensks fiskeldisfóðurs til ræktunar á beitarfiski og meta hvaða plöntur henta best í framleiðslu með samrækt. Sex mismunandi kerfi voru byggð í rannsókninni og mælingar framkvæmdar á þeim til að meta samspil þátta innan kerfisins og áhrif þeirra á stöðu kerfisins. Eitt kerfið var NFT kerfi, fjögur voru svokölluð DWC kerfi og eitt var flood and drain kerfi. Eitt DWC kerfið var byggt í iðnaðarhúsnæði, þar sem notast var við raflýsingu. Tilapia eða beitarfiskur er einn vinsælasti eldisfiskur í heimi og var ræktaður í öllum kerfum á meðan plöntuval var misjafnt milli kerfa og samanstóð bæði af blaðgrænmeti sem og ávaxtaplöntum. Fiskarnir voru fóðraðir á eldisfóðri fyrir sjófisk og bleikju og fóðurstuðull þeirra reiknaður. Fóðurstuðull er mælikvarði á hversu vel fiskurinn vex og er jafnan á bilinu 1,0 og 1,8 fyrir beitarfisk. Í þessari rannsókn var fóðurstuðullinn á bilinu 0,9 til 1.5. Blaðgrænmeti, sérstaklega pak-choi skilaði góðum niðurstöðum í kerfunum, sambærilegum við aðrar rannsóknir. Ávaxtaplöntur skiluðu ekki eins góðum árangri.

Aquaponics is a method of producing food in a sustainable manner where fish and plants are grown together in a closed loop of nutrients. An aquaponics system is comprised of fish rearing tanks, mechanical- and biological filtration and hydroponics units in a closed loop of nutrients. Fish waste produces nutrients for the plants in the hydroponic unit consequently removing nutrients from the water column to make the culture water more suitable for fish. The purpose of this research was to evaluate and calculate the production of tilapia and different aquaponic vegetables through a study period of two years. The suitability of locally available feed and the selection of plant species were assessed. Effects of water flow on plant growth and nutrient utilization were measured. In this study, six aquaponics systems were built in four different places. One of the systems was a nutrient film technology system whereas four were deep water cultures. Moreover, a flood and drain system was built and tested. One system was built within an industrial building and received artificial lighting while the others were all located inside greenhouses. Tilapia, which is one of the most popular fish in aquaculture, was reared in all systems while different leafy green and fruiting plants were grown. The fish were fed commercial aquaculture feed for cod and charr. The feed conversion ratio is used to assess how effective the fish’s growth is, typical FCR for tilapia is between 1.0 and 1.8 depending on the feed quality and environment. The FCR observed in this research was between 0.9 and 1.5. Leafy green plants especially pak-choi showed similar yield to other research, expected approximately four times the production of fish in mature systems. Fruiting plants did not do as well as leafy greens in this experiment.