Tuesday, April 3, 2012
Aquaponics: The Key to a More Sustainable Future?
It’s becoming increasingly evident that we’re going to run out of sustainable fish stocks in the years ahead—is aquaponics really a viable solution?
The world is always changing around us and the face of agriculture and food production is changing as well. A constantly increasing world population means more urban sprawl is taking over what was once fertile farm land—how are we going to manage to grow enough food to keep up with our ever-growing numbers, especially the millions who live in drought-stricken, arid climates? Fish numbers are also dropping throughout the world’s oceans, leading experts to predict increasingly severe global shortages.
How about aquaponics? Aquaponics is an ingenious growing system that merges edible fish production with hydroponics. In aquaponics an artificial ecosystem is created in which fish are fed, their waste is broken down into more absorbable forms by beneficial bacteria and the converted waste is then pumped through the system, where it feeds the plants. The plants act as a natural filter, cleaning the water—which is then recirculated through the system. Aquaponics is looking more and more like it’s going to be one of the best solutions for future generations seeking sustainable ways to produce healthy organic food.
Making aquaponics work
Aquaponics is a blending of two important ideas, combining fish farming with hydroponics (soilless gardening). Edible fish that do well in closed environments are required—tilapia, white bass, crappie and barramundi are species that are used in many commercial and home aquaponic systems. These fish will feed and their urine and feces will be a waste product. In normal fish tanks or fish farming systems the waste builds up and makes the water toxic to the fish—the waste-filled water then needs to be purified and would normally be either filtered or disposed of.
In aquaponic systems this is not the case, however—the fish waste actually makes great plant food. The waste-filled water is recirculated throughout the system instead of being flushed away. One very important aspect of aquaponics that needs to be understood is that it is not just a symbiotic relationship between fish and plants—there is another system of organisms operating within every aquaponic system that is crucial to success. This is the network of beneficial bacteria that needs to exist in every aquaponic set-up. The beneficial bacteria nitrosamonas spconverts ammonia from fish urine and feces into nitrite and the beneficial bacteria nitrobacter sp then converts the nitrite into nitrate—a form of nitrogen that plants can absorb and fish can tolerate in their water at low levels. Without the action of this network of beneficial bacteria the water would develop toxic levels of nitrite (even small amounts are toxic) and both the fish and plants would eventually die.
This network of beneficial bacteria is fragile and must be cared for as carefully as your fish or plants. This means that you can’t use any chemicals—including hydrogen peroxide or pesticides (chemical or organic)—that could harm the beneficial bacteria. If you stick to these rules you can create a healthy system of ‘good’ bacteria in your aquaponic system. Bacteria need a lot of surface area to thrive—raft and deepwater culture systems have enough surface area for the beneficial bacteria to grow but systems such as NFT (nutrient film technique) do not. In NFT systems you have to help the bacteria by creating a biofilter, which can be accomplished by adding a separate chamber to the system that the waste-filled water will have to pass through. In this chamber a piece of mesh should be strung from side to side, providing adequate surface area for the bacteria culture. You could buy bacteria and add them to your system but this is not really necessary as they will develop and grow naturally if allowed to.
For beneficial bacteria to thrive a neutral pH balance of seven should be maintained, unlike hydroponic systems where the pH should be kept slightly acidic at a level of 5.8 to 6.8.
There are many reasons to choose commercial and small-scale home aquaponic systems over traditional methods of farming fish and vegetables separately. Environmental concerns are one big reason that aquaponic systems are being looked at seriously as an important future source of food—aquaponics will eliminate the need for the costly synthetic nutrients that are often used in hydroponic systems. These synthetic nutrients are made using fossil fuels and many experts believe that we have reached the peak level of oil production. This is a controversial topic and is very debatable, but either way these fossil fuels could be better used in other ways, such as heating and powering homes.
Another environmental benefit aquaponic systems have over other farming options is that you don’t use pesticides when farming with aquaponics. Pesticides that are normally used to control and eliminate insects are harmful to the fish in aquaponic systems. Although most pesticides in use today are considered relatively safe, there are many that are not—and not all countries enforce the same strict pesticide laws that protect us in North America.
Aquaponics is also advantageous in that it conserves water. Fish farms must either use expensive filters to purify water before it is recirculated, or—more likely—dirty water is just flushed and fresh water is then used to replace it. Water used in hydroponic systems must be replaced often as well—salts and minerals that are not absorbed by the plants can build up, reaching toxic levels quickly. In aquaponic systems plants absorb the fish waste, acting as a natural filter. In this way water can be continuously recirculated, only occasionally needing a top-up to make up for evaporation and plant transpiration.
The capability of aquaponic systems to recirculate water efficiently could be very beneficial in arid regions of the world where so many countries are now facing drought and food shortages. Aquaponics looks like it could be a great solution to those problems—by recirculating water, aquaponics systems should allow people to grow more food with less water. Since aquaponics doesn’t require synthetic nutrients or pesticides either, it can be a very cost-effective means of feeding many people. Aquaponics could also be established on a large scale outdoors in warmer climates to utilize the sunlight.
People love fish—it is highly nutritious and at one time the supply of most species was so plentiful as to appear inexhaustible. Now, due to overfishing, climate change and lax regulations the world’s stocks are rapidly dwindling and it seems more and more likely that fish farming will have to become the way of the future. If we are serious about finding a sustainable way for future generations to acquire the nutrition that fish can provide, we must take a long look at aquaponics.
The world continues to change and the population is going to keep growing. Climate change and ever-expanding urban sprawl are taking away fertile land that was once used for agriculture. Fish stocks are plummeting, while large-scale farming on land reduces the natural habitats of animal species. We are at a vital crossroads and the well-being of future generations depends on which road we take—it’s beginning to seem more obvious every day that aquaponics could be a very important part of the solution to our planet’s impending food shortages.