Science Behind Aquaponics
History of Aquaponics
Aquaponics takes traditional aquaculture (the raising of fish) and crosses it with hydroponics (the raising of plants in water). It is a farming method originating from 6th Century Southeast Asia, when farmers introduced fish to eat pests in rice paddies. The fish fertilize plants via the nitrogen, phosphorus, and carbon cycles, and the plants take in various nutrients via their root systems. Aquaponic farming has been proven to use less water to grow the same amount of food. In a Saudi Arabian study, only 1.4% of the water had to be replaced daily because of evaporation and transpiration losses. (vi)
Why Choose Aquaponics?
According to the World Economic Forum, the water crisis is the number one global risk in measurable damage to modern society (i). Although the amount of water on earth has not changed, the distribution of water compared to major centers of population has changed. Some regions of the world have major stockpiles of water resources, while others have little fresh water or little clean water. Even though “nearly 70 percent of the world is covered by water, only 2.5 percent of it is fresh. The rest is saline and ocean-based. Even then, just 1 percent of our freshwater is easily accessible, with much of it trapped in glaciers and snowfields. In essence, only 0.007 percent of the planet's water is available to fuel and feed its 6.8 billion people (ii)”. With climate change and rising population levels, the United Nations estimates that by 2025, over 1.8 billion will be living in water stressed areas.
As of 2015, 864 million people (or approximately 1 in 8) live in areas without access to clean water (iii), and 805 million people (also approximately 1 in 8) live without access to food (iv). With these numbers so similar, one can only wonder if they are directly correlated. Since the agricultural sector relies heavily on the availability of water, and the global population rising towards an estimated 9.6 billion by 2050 (v), how will we feed all of these people?
Science & Benefits
“Because aquaponically grown plants have plenty of everything they need at the root zone – water, oxygen, and nutrients – each plant need grow only a minimal root system to supply its needs.” (vii) Thus, ten acres worth of traditionally farmed food can be produced in only one acre using aquaponic grow methods. The same Saudi Arabian study found that net fish production averaged 33.5 kg/m3 of water with the overall water consumption being 320 L/kg. Further, the production of leaf lettuce was 42 heads/m2 of hydroponic surface area. The researcher did note that the number of heads of lettuce should be reduced to under 30/m2 in order to produce higher quality lettuce. This is still over the 16-24 heads/m2 recommended by the BC Greenhouse Grower’s Association for traditional gardening methods (viii).
Furthermore, with a global increase in the demand for meat, aquaponics would be able to provide a more sustainable protein source. Cattle require 4.67 pounds of feed to produce one pound of meat (ix), while tilapia need only 1.6 pounds to produce one pound of meat (x) Compared to warm blooded cattle who need to use energy to keep themselves warm, cold blooded tilapia do not have this requirement, saving an estimated 80% of their energy (vii). This energy savings contributes to the three pound drop in required feed and greatly increases sustainability, as more food is available for human consumption and have reduced land requirements.
Aquaponics systems have additional benefits:
Ability to clean the water. By running water through a gravel grow medium with various plants, the water is cleaned of organic compounds (Nitrogen and Carbon compounds). This provides a healthier environment for locations with impure water. In colder climates, fish such as catfish and carp that are more tolerant to colder weather could be raised.
A source of protein in fish. Warmer regions of the planet would be able to raise tilapia for consumption without major energy use. In aquaculture, bottom-of-the-food-chain fish (vegetarian) are healthier to eat than top-of-the-food-chain fish (predators) (xi), and tilapia are the industry standard. They are a hearty fish, being from heavily polluted and oxygen-starved rivers and lakes in Africa, and thus dirty or impure water would not affect their growth, making an aquaponics system an ideal solution for areas without a large amount of clean fresh water.
If a source of protein isn’t a priority, aquaponics.com suggests raising fancy goldfish, Koi and smaller ornamental fish like guppies and mollies. They also recommend planting leafy lettuce, leafy greens such as pak choi, kale, swiss chard, and arugula and various herbs. In established systems, plants such as tomatoes, peppers, cucumbers, beans, cauliflower and cabbage can be grown as mature aquaponic systems can meet the higher nutritional demands required by these types of produce (xii).
Some companies have ready to go fish-tank-top systems that are smaller and good for demonstration purposes in classrooms and organizations. These tank-top systems limit the type of produce one can grow and the type of fish that can be raised. For instance, a 20 gallon fish-tank-top system will only be able to grow small herbs, lettuce, and other smaller, leafy greens and support guppies, mollies and other small fish.
A new, 21st century trend in urban environments is the grow wall. Normal grow walls are full of soil and use a water-wasting drip system. Aquaponic grow walls use either a series of vertical or horizontal pipes that recirculate water into a fish tank. One major advantage of this type of system is the saving of space, increasing practicality. However, it is important that larger (4” or greater in diameter) pipes are used to prevent roots from clogging the pipes.
If a large-scale system is desired, a media bed system can be built. This kind of system is very similar to a raised grow bed garden, except that it is soilless. A media bed system is the easiest to expand and allows for the most diversity in crops and fish. The only downside, however, is a larger space requirement as the media bed system occupies more horizontal area.
In addition to saving water, aquaponics also has multiple other benefits.
1. Aquaponics allows for food to be grown closer to the consumer, and thus food would be fresher at the time of consumption. Farming takes 10% of the total U.S. energy budget, 60% of U.S. land, and 50% of U.S. water supplies. Even though the U.S. produces more than enough food to feed all of its citizens, 40% of food is wasted due to spoilage during transport, purposely not harvesting and consumers not eating the produce in time. Aquaponics would eliminate the spoilage during transport, drastically reducing the percentage of wasted food. By utilizing vertical and tank-top style systems, people in cramped apartments could grow their vegetables and herbs, whilst larger media bed systems would be able to provide tomatoes, peppers, and in some cases: bananas (xiii) and other fruit trees.
2. Aquaponics also has the benefit of not containing heavy metals and pesticides. Unless using tainted water or purposely adding any other chemicals, aquaponically grown food will not contain lead, mercury, arsenic, or pesticide residue. In New York City, after a heavy metals test was requested, a lead sample of 1,251 ppm (triple the federal guideline of 400 ppm) along with an arsenic sample of 93.23 ppm was detected in the Sterling Place community garden. In an additional 38 of the city’s gardens, toxic soil was present (high concentrations of lead, arsenic, and pesticides). After multiple years of exposure to lead from various sources, the urban youth may begin to feel various health effects such as behavior issues, brain damage, cancer and seizures.
3. As consumers’ knowledge expands, their food preferences change. The buy local, buy sustainable movement is rapidly spreading in the U.S. In fact, the USDA found that direct-to-consumer food sales tripled from 1992-2007 ($404 million to $1.2 billion (vii)), a trend that is continues today. The National Restaurant Association found that the top two menu trends for 2014 were locally sourced meat and seafood and locally grown produce while the National Grocery Association found that 87.2% of consumers rank availability of locally grown produce and packaged foods as ‘very/somewhat important’. Aquaponics would be able to provide this food even more sustainably since aquaponics provides a natural fertilizer – fish waste, which cuts dependency on ammonium based fertilizer.