A Critical Evaluation Of Aquaponics

Aquaponics can be defined as a semi closed system in which requirements for the cultivation of fish and plants are continuously cycled. The process can best be described as a combination of hydroponics, and recycling aquaculture in that it’s a system that combines the growth of plants solely in nutrient rich water (removing the need for soils), with the cultivation of fish in a water cycle (Oxford Dictionaries, 2012). The concept behind the process is that a source of food is fed to the fish in the tank; effluents build up including ammonia which is pumped into a bed of stones containing bacterium which converts ammonia from the fish effluents into nitrates via nitrification, these nitrates aid plant growth on a medium such as gravel or clay pebbles, the water then filters back sans ammonia into the fish tank where the cycle begins again.

This effectively means that the only two continuous inputs are energy to power the pump, and food to feed the fish. It removes the need to use nutrients from soil, including the need to fertilise intensively farmed soils, and reduces water use in the long run. The idea is to cultivate plant produce such as lettuce and to (on larger scale aquaponic set ups) cultivate fish for consumption such as Tilapia. The theory behind aquaponics and its application are relatively new, although there is evidence behind ancient implementation of similar practices such as the cultivation of rice in South East Asia in addition to fish such as Oriental Loach (Kaori, et al, 2009). Therefore, the science behind aquaponics, including academic research into the topic is relatively thin on the ground, although with modern demand from an increasing global population, this is set to increase exponentially.

There is substantial promise and benefits to be gained from the aquaponics theory. As mentioned, a rising population, particularly in urbanised areas with limited space means that the versatility of the process is extremely valuable. However the practise does have criticisms to do with the sustainability of raising fish on such an intensive scale, and the complexity of the process when compared to traditional farming and gardening. Aquaponics has a clear relationship with fisheries and agriculture, as can be seen by the aquaculture and crop yield components, however evidence also suggest that aquaponics also relates to conservation and restoration ecology, in that this form of agriculture and aquacultures are both less demanding in terms of space.

The aquaponics process relies on a series of initial investments to start it initially – a holding tank for the livestock, a pump, grow beds, and a growth medium. Alongside this, there needs to be a continuous input of water (on a small scale after the initial fill up), electricity, and fish food in whatever form such as traditional feed or black fly larvae. It is argued that this means aquaponics is a much more sustainable system than traditional agriculture. (Sikawa, 2010) It can also be argued that the system is more efficient than hydroponics (which also removes the need for soils – the most unsustainable part of intensive agriculture) since there’s no need to add nitrates into it. Therefore it can be argued that aquaponics is a vastly superior form of agriculture in terms of sustainability.

However, it can be argued that despite clear improvement on unsustainable practises in other forms of agriculture (soil use and fertilisers); aquaponics is not as sustainable as initially suggested. The main evidence to support this is the use of fish food to feed the fish livestock; in larger and commercial aquaponics set ups the feed (fish food pellets rather than flakes) is typically made up from smaller bait fish which have been grown especially to be ground up into fish food, or from by catch not fit for human consumption (IFFO, 2006) (although, it is possible to harvest black fly larvae or duckweed to support fish stocks). This practise means that fish food, more so on larger scales, is an unsustainable form of feed, thus making intensive aquaponics systems an unsustainable practise.

Despite this, in comparison to traditional cash crop agriculture, and greenhouse culture – it removes the intensive pressure upon soils, and removes the need for fertilisers. Compared to agriculture with rotational crops (e.g. one year wheat, one year potatoes, one year left to recover) it can still be argued to better reduce the unsustainable pressure on soils. Compared to hydroponics, it can be argued to be more sustainable since it doesn’t rely upon nutrients being added via fertilisers. Aquaculture too, can be argued to have the same unsustainable flaw as aquaponics, in that they both require fish food to be added to the cycle. Therefore, aquaponics can be argued to be more sustainable than many forms of agriculture and aquaculture, but it cannot (in its intensive form) be argued as entirely sustainable.

Evidence also shows water conservation, with one scientist (Lennard, 2005) suggesting that water use may be less than 10% of the water required for a standard yield via traditional intensive agriculture – being evidence to support the claims of improved sustainability versus other forms of agriculture. Alongside this, aquaponics is easily compatible with other sustainable practices. For example, vermiculture can be practised by using the organic waste from harvested yields to feed worm growth, which in turn can be used as fish feed. And the inclusion of a compost module inside a greenhouse containing an aquaponics set up (also by utilising organic waste such as the discarded fish parts) can be used as a free heat source; this will increase growth and the growing season thus increasing the yield.

Further evidence shows that the reduced need for land and water (Robertson, 2005) space compared to typical intensive agriculture (since yields are higher in smaller spaces) means that less erosion occurs, since if aquaponics reaches the popularity where it reduces the amount of intensive outdoor agriculture that occurs, less ploughing of fields will occur, and a reduced amount of land will lay bare over winter when the most weathering occurs. Evidence suggests that a reduction in land used for agriculture means that more land will/ can be used for other forms of land use. For example, if agricultural land is returned to a more natural state, this can mean greater biodiversity occurring – something that has a lot of resources contributed to.

Evidence suggests that aquaponics has the potential to be a large scale and viable food source in a vast range of environments. Since the system relies primarily on sunlight, shelter/ warmth, electricity and a variable amount of water, it can be implemented wherever these conditions are met, i.e. in buildings worldwide, and many outdoor tropical locations. This makes it an incredible versatile form of agriculture, for many variations are possible, e.g. a saltwater paradigm. One example of this is the implementation of urban agriculture and aquaculture in the form of aquaponics, this is especially important in modern agriculture since food and space demands are at their highest ever levels, and with urban populations now being higher than rural population, maximising productivity is becoming ever more essential. To add to this, creating artificial conditions for agriculture and urban populations being far from areas of typical agriculture means that food miles and carbon release can be reduced by growing crops locally, especially ones that won’t survive in that environment outdoors, e.g. chilli’s can be grown indoors in the UK.

To add to this, evidence shows that agriculture conducted indoors such as hydroponics, and of course aquaponics suffers significantly less yield loss when compared to outdoor ‘normal’ agriculture, especially pesticide free organic crop yields that are becoming increasingly popular. This is because of a combination of having a more controlled environment which minimises the risk from flooding and drought, as well as reducing pathogens and pests that feed upon the crop yield, as well as affect the fish stocks – with fish diseases being a significant problem that affects the high density aquaculture systems, compared to the very low density wild fish stocks which are effected much less (Tidwell, 2012).

There’s also evidence to suggest that the quality of produce grown in an aquaponic system is very high, for example there’s a lack of both artificial pesticides and fertilisers used in the entire system, since the system is heavily regulated, in an artificial environment, and apart from fish feed it’s a closed system. Further evidence to support this is the quality of the nutrients from the nutrient cycle, in that it’s clearly (as can be seen by the rates of growth) comparable to a good quality soil (Rakocy, et al., 2004). Speed of the growth of crop yield and fish stocks are variable, the variables being; pH levels, heat in terms of both the water and the air temperature, whether the set up is indoor (most common) or outdoor, the fish to plant ratio, the age of the set up, and the growth medium.

The fish stocks in an aquaponics system are vulnerable since they are high density to fish disease if an infected individual is added. The inclusion of an infected individual is very unlikely and much more manageable than infection control in an aquaculture system, due to the scale and often because they are in the ocean. The increase protection was having a more controlled environment also means that no pesticides have to be used (unless an infection is identified from an outside source), and the nutrient cycle system means that fertilisers also don’t need to be used. Therefore, evidence suggests that aquaculture has significantly higher yields due to a combination of an increased survival rate, and greater protection from the elements, as well as the protection of the nutrient sources.

However, there is evidence supporting criticism of the viability of aquaponics as a large scale food source. Primarily, there’s an issue regarding the acceptance of a food source that is considerably different from ‘traditional’ agriculture, especially given the modern day demand for ‘organic’ produce. Consumers may be put off by the thought of food grown without soils, or being fertilised by fish effluent, regardless of how organic or intensive agriculture have their nutrients provided. Another issue is related to this is acceptance of the fish crop, Tilapia can be argued as most suitable for aquaponics (since they are hardy, freshwater fish) – this is not a widely eaten fish in the UK, although other foreign populations may be more accepting, and the British may take to it soon (BBC, 2009), and there’s difficulty in the suitability of other fish that would be eaten by a British population, e.g. trout – their size and space demands being an issue.

Although the requirements in terms of labour are relatively low, they do still have a significant financial cost, and a financial commitment for its maintenance, this may be an issue for many potential aquaponics farmers. To add to this, it is arguably much more complicated than normal small scale agriculture where planting your crops and occasional pruning is most of what’s necessary, whilst aquaponics requires a correct set up, monitoring and maintenance. In regards to the variables that affect the rate of growth; pH is important since it slows the nitrification capacity of the bacterium, which in turn slows down growth rates of the plants. Heat is explanatory, since lower temperatures mean less growth, this includes fish stocks, also to be noted is that many fish require certain and different temperatures to realise their growth potential. General build quality and design have large impacts too. (Storey, 2012)

The growth medium also affects the rate of nitrification since more bacterium means more nitrification, different types of growth mediums have different surface areas and suitability. The fish to plant ration also matters because if there’s an imbalance, there can be ammonia build up causing deaths amongst the fish (if there’s too many fish), and poor growth rates can occur if there’s too little fish, or too many plants (Rakocy, et al. 2006) As the evidence suggests, there’s many complications that affect productivity. Despite this, aquaponics can be argued to be far less complex and cheaper than hydroponics and aquaculture are, and require less initial investment. Because of these requirements, it can be argued that aquaponics would be unlikely to overtake modern agriculture as the main food source for a very long time.

As the above evidence suggests, aquaponics does have a large potential as a widespread and viable food source mostly due to its versatility and low resource requirements, however – it can be seen that there are several factors which set major limitations that affect this potential. Regardless, it can be concluded that there is a significant avenue for potential in food production and adoption via aquaponics, once the major limitations such as standardising the information (see later) have been overcome, as well as the need for adapting current systems to suit different markets, and addressing the lack of information altogether have been overcome.

What’s more though, aquaponics has the potential to be implemented alongside alternative sources of energy. For example, because of the energy requirements and the need for sunlight for the crop, solar energy is often a viable form of energy to supplement the pump – this will in turn drive forward investment in solar energy, which regardless of other factors, reduces energy reliance on fossil fuels. This means that hydroponics has a slight capacity to increase renewable energies although this is relatively unproven, the evidence to support this is that many participants goal in aquaponics is to create a renewable food source, or in commercial farms, the/ a goal is to maximise profit.

Aquaponics is a very new ‘science’, with its beginnings starting in the 1960s via the ‘New Alchemy Institute’s creation of an ‘ark’ – a bio shelter using sustainable cycles to support a family of four (Todd, Todd and MacLarney, 1969). Because of this, research conducted and information about the process is particularly scarce. Evidence suggests that the process has a huge potential, and potential for research. This is also backed up by commercial potential which can become a significant driver behind advancement as evidence shows such as the massive investment in organic farming occurred once it became apparent there was a market for it. To add to this, evidence suggests that educational and financial investment will occur, this means that aquaponics is a strong contender for scientific research, and to make money.

Despite the scientific and financial interest, there is the potential that the relative newness and how unknown the topic is currently has negative effects on its viability and potential. There is the possibility of market contenders hindering investment and progress of competitors in order to reduce competition as evidence suggests occur (as can be seen in ‘patent battles’ in research technology in general). The little research conducted may prove too daunting for amateurs and beginners to invest their time into if they are unsure of exact details and results. This hindrance of grassroots organisation and investments of time and energy can result in a slowdown of contributing to the science.

To continue this avenue of criticism, system failure and the massive variability of results can both be detrimental for the viability of aquaponics. For example, the system entwines electronics and water containing fish stocks – incidents can and does occur where system failure has resulted in the loss of an entire yield (e.g. from electrocution); another example is the inclusions of ammonia sometimes used to kick start the cultivation of the bacterium that converts ammonia into nitrates, too much of which can kill livestock. And, since aquaponics relies on a cycle, it can have detrimental effects on the other half of the yield grown – it can also mean the whole cycle will have to be reset and started again. Therefore, the evidence suggests that aquaponics has significant issues that are detrimental to the continuation and progress conducted in the field of aquaponics such as it being relatively unknown, and having little research conducted, as well as the variable and volatile results.

Evidence also shows the viability and usage of aquaponics for scientific research. Hydroponics has long been used to scientific research; this is because of several benefits over traditional soil based agriculture: namely the increased stability allowing more standardised results, e.g. reduced water, less disease potential, easier harvesting and yield stabilisation. Aquaponics, alongside hydroponics and other variation of ‘ponic’ agriculture (‘ponic’ meaning labour or grown in an artificial manner) such as aeroponics (an environment with a fine mist) and ‘bubbleponics’ (highly oxygenated and nutrient rich bubbles) has an established and establishing scientific use, as can be seen by NASA’s ‘Controlled Ecological Life Support System’ (CELSS) research and its funding of aquaponic research, this is to identify uses for terraforming and for long term (i.e. for several years long) space exploration – for use in the future. (AG Horticulture, n.d.)

Conversely, evidence does suggest that for the scientific community, hydroponics may be the preferred and most suitable form of agriculture, and that aquaponics has factors that inhibit its usefulness and potential for scientific research; mainly that the inclusive of an aquaculture element is an unnecessary inclusion that complicates and increases any workload that only requires the crop yield rather than the fish stock element. For example, research in biology that requires a yield of quickly grown crops such as lettuce would not require a yield of Tilapia – which would be unnecessary, as well as an unneeded expense when research funds are often already limited. Therefore, evidence suggests that as a scientific tool, aquaponics is viable for some forms of research, and naturally can be the subject of massive amounts of research; however for a large part of the scientific community, hydroponics or aquaculture may prove to be far more suitable for meeting the requirements of the research.

Commercial viability is typically one of the main driving forces behind the advancements in scientific research. There are many, many examples of this ranging from the oil industries drilling technology being well advanced due to the massive market for fossil fuels (e.g. deepwater drilling in the Gulf of Mexico that became economically viable with rising oil prices, meaning that investment into the technology began) to the investment in the Panda breeding program, which was partly fuelled by the tourism money it brought into China (Chengdu Panda Base, 2007). Therefore, if aquaponics is commercially viable to be a competitor to aquaculture, and agriculture – it can be argued that financial investment in the system will increase, speeding up development.

Due to the versatility of the system, it can be adapted to grow a wide variety of crops such as herbs, spices, vegetables, and fruits, with root vegetables typically being the major group that is unable to be grown. On the livestock side, many types of fish can be grown (although typically freshwater) including trout, perch and catfish – the most common fish is Tilapia. Due to the vast variety of plants and fish that can be grown, and other factors such as climate, nutrient balance and construction quality, it is very difficult to determine is a profit can be made on that particular set up – and that aquaponics in general has the potential for economic investment and return.

Looking at prior evidence does suggest that yields from an aquaponics system are typically higher than those of a field based production in terms of agricultural yield. For example, research by Nick Savidov, 2002 in Alberta, Canada (a prime market location in that it’s too northerly to grow their own hot weather crops such as bell peppers, and with a large enough population so there is a demand) with technical assistance from Dr. James Rakocy showed that tomato crop yields in an aquaponics system were 10-15% higher than field yields, as well as 100 cucumbers per meter-2 a year – far exceeding organic greenhouse yields in the region, Savidov suggests.

Research conducted by Rakocy, et al (2004) the University of the Virgin Islands (one of the world leaders in aquaponic research, as well as where Rakocy is based) shows that basil production yields far exceeded those that could be grown in the field. His research showed that the aquaponic set up in the Virgin Islands produced 7.8 kg of basil m2 a year in field production using a ‘staggered’ technique where a yield of a certain size was planted in order to mature at different dates – ensuring a continuous harvest. This is compared to aquaponic production of 23.4 kg m2 of basil was produced in a staggered set up, whilst a ‘batch’ production (i.e. all crops were grown to capacity at the same time and repeated for the year) resulted in 25 kg m2 of basil in a single year, it should be noted however that Rakocys research concluded that the batch production was unsustainable because of the stresses it put upon the fish stock for nutrients.

Regardless, income provided by batch, staggered and field production were: $117700, $110210 and $36808 respectively across the 214m2 production area (USD in 2004 values). This is not including the Tilapia harvest, which was staggered to harvest every six weeks; Nile tilapia were stock at 77 fish m3 and Red tilapia were stocked at 154 fish m3 – with a total capacity of 31.2m3 divided into four 7.8m3 tanks. Projected annual production was 4.16 mt and 4.78 mt (metric tonnes) for Nile and Red tilapia respectively, the report didn’t value the Tilapia, although ‘Globefish, 2011’ (Food and Agriculture Organisation funded, represented by the UN) reported a 2011 USD price of 1.30-2 per kg of fresh tilapia with 0.95 USD being a good price for farmers, meaning that the University of the Virgin Islands has an annual yield potential value for the four year experiment of 8940 kg of $8493 to $17880 per year. Therefore, this evidence shows that under these conditions (water stressed Virgin Islands, US economy, local climate, professional guidance) that a substantial income can be made after initial investments in a large scale production facility; this means that evidence shows there is significant potential for economic return once initial investments has been made, which Rakocy(n.d.) agrees to.

In conclusion, evidence shows that aquaponics has significant value in terms of food production, commercial viability, scientific value for research, and sustainability for long term use, throughout the world. It also has massive potential for these factors, and evidence suggests that aquaponics will expand in terms of popularity, food production as well as commercial and scientific interest. As a result, it can be concluded that aquaponics has its faults, but in general it is a valuable and worthwhile system with great potential.