Aquaponics is an agricultural technology that combines aquaculture and hydroponics through a simple, symbiotic cycle. This method was used by ancient civilizations across the world but after being cast aside it is now gaining traction as an environmentally sustainable urban agricultural technology.
Hydroponic technology relies on growing plants in expensive, nutrient rich water. Hydroponic farms also face significant waste disposal challenges as this nutrient rich water needs be periodically flushed out of the system. And when released can upset the balance of the ecosystems in and around the farm, in bodies of water; such as lakes and rivers.
Aquaponics solves these shortcomings by rearing fish in conjunction with growing plants. The waste rich water from the fish tanks is used to feed the plants thanks to the help of naturally occurring bacteria. And the cleaned water is recycled back into the fish tanks. A very minimal amount nutrients need to be artificially introduced to the system, making it a highly sustainable closed loop system.
We spoke with Crop Circle Pvt Ltd, a Sri Lankan aquaponics company, to find out more about how this highly sustainable agri-technological system works and what challenges are faced in implementing it here in Sri Lanka.
Aquaponic systems mimic natural waterways (P2)
How an Aquaponics System works
Aquaponics mimic the inherent process of every natural waterway on earth. Allowing for highly dense farming, in urban areas, in a sustainable manner. The main input of an aquaponics system is fish food. The fish excrete waste in the form of urine and fecal matter. The fish urine contains ammonia and their fecal matter is also broken down by heterotrophic bacteria to ammonia. Although in excess concentrations, ammonia can be toxic to both the plants and the fish, nitrifying bacteria convert the ammonia to nitrite and then to nitrate, which is consumed by the plants. These heterotrophic and nitrifying bacteria are naturally occurring in environments where ammonia and nitrite are available and latch on to the tank walls, rafts, organic matter, growing medium, and water columns of the aquaponics system.
Therefore there are three species that you need to keep in balance to maintain an efficient aquaponics system: the fish, plants, and beneficial bacteria. These three species create a symbiotic process, relying on each other to survive. The bacteria consume the fish waste providing the plants with nutrients essential for their growth. While the plants also pull the nutrients from the water, maintaining a habitable environment for the fish.
Aquaponic produce from Sri Lankan Company Crop Circle Pvt Ltd (P3)
History / Origins of aquaponics
Aquaponics is not a modern invention. In fact, its origins can be traced back to ancient Asian, and Aztec civilizations. More than 600 years ago, the Aztecs who settled on the marshy shores of Lake Texococo, in Mexico, created floating platforms made from reeds and mud called “chinampas”. On these floating platforms they planted a variety of crops and created a farming practice that sustained their entire population. This method was so successful because the roots of the plants reached the lake water, which allowed them to absorb nutrients produced by the aquatic organisms in the lake. (1)
Even further back, 1,700 years ago, the Chinese implemented a rice-fish farming method that leveraged the benefits of aquaponics. This method went into decline in the 1960’s and 70’s due to the extensive use of pesticides as well as the unfavorable economic policies of the Chinese cultural revolution. But in recent times, it has seen a resurgence. China now has the largest functioning aquaponics system in the world; a four acre floating farm on Lake Taihu. This floating wetland was designed as a measure to remove nutrients that enter the lake when excess fertilizer is washed into it from surrounding farmlands, which creates unhealthy algal blooms. And unlike rooted wetlands, floating wetlands rise and fall with the water level. Which means that the plants don’t die, with fluctuations to the water level, and release nutrients back into the water.
The fish reared in an aquaponics set up is also a source of revenue that can be extremely lucrative if you the right breeds are selected (P4)
Benefits of Aquaponics Systems
There are a wide range of benefits to implementing aquaponics systems compared with traditional farming methods. For one aquaponics systems have a lower dependence on water, saving up to 90% of its water. While traditional methods lose large quantities of water over time due to wastages from evaporation and percolation, which is when the water seeps through the soil. (2) Also in aquaponics, there is no need for additional fertilizers since the nutrients for the plants come from the waste created by the fish. Aquaponics systems are also highly resistant to pests and disease as they are maintained within enclosed structures, like greenhouses, which protects the plants. This is combined with the fact that the plants are grown in moving water, and not soil, there is no medium through which disease can reach the plant. The entire setup can be automated, significantly reducing labour while improving the quality of the produce by providing an ideal environment, and an optimum delivery of nutrients for the plants to grow.
As a result it is possible to reduce to the cultivation periods of many types of vegetables. Leafy greens can be grown in 4 to 6 weeks, while vegetables and fruits take 8 to 10 weeks. Using conventional methods this cultivation period can take double the time. Varieties of produce that can be cultivated include; lettuce, carrot, basil, celery, tomato, pea, spinach, aubergines, chard, savoy, cabbage, hot pepper, cauliflower, beans, cucumber, saffron, strawberries, and several varieties of flowering plants.
The absence of harmful pesticides, in aquaponic systems, also means a natural organic produce which is increasingly in demand in developed economies. Furthermore, aquaponic systems require far less energy demanding than traditional methods. The main energy input of an aquaponics system is for the power supply that activates its pumps and aerators. The other main input, as mentioned before is fish feed. A wide range of freshwater fish such as tilapia, trout, catfish, eel, carp, crayfish, and ornamental species such as goldfish and koi carp can be reared as part of an aquaponic system.
There is unfortunately a lack of knowledge and talent needed to appropriate such systems for our climate on a larger scale (P5)
Challenges of Implementing an Aquaponics System
While there are many benefits of implementing aquaponic systems, they are not without their own challenges, especially in a country like Sri Lanka. Modern aquaponics systems in the market are not designed for tropical climates, making it impossible to implement off the shelf solutions successfully. Aquaponic systems are less labour intensive but require highly skilled persons with knowledge and experience in both aquaculture and agriculture, which is a challenge to find in the present job market.
In addition to this organic certifications are currently awarded based on soil testing. Therefore it is presently not possible for companies to receive organic certification for aquaponic produce, which would allow them price their produce at a better rate to recover the costs of setting up such a system. The lack of investment and knowledge in aquaponics systems make it challenging to introduce to the local agricultural sector in Sri Lanka, which is highly matured. This needs to be overcome if aquaponics is to grow. Crop Circle constructed their aquaponics system with 100% locally purchased equipment and material, so it goes to show that it is in fact possible to set up and execute aquaponics operations in Sri Lanka. However in order to develop this fledgling but potentially revolutionary technology, more organizations need to invest in R&D to optimize this solution to suit our tropical climate and identify the ideal produce to maximize the return on investment.
Aquaponics needs to come out of the experimental closet into the mainstream (P6)
It is quite clear that aquaponics presents a highly sustainable, low-energy, solution to growing agricultural crops. Its symbiotic nature yields greater harvests, presenting a viable and ecologically sound alternative to traditional cultivation methods. Although it is full of potential, greater focus should be given to develop this technology in Sri Lanka. An updated method of organic certification also needs be introduced to promote its adoption. To find out more about other agricultural technologies, please click here.