I had no idea what to expect when I first came across an aquaponics system. In fact, I didn’t expect it at all, because I was on a tour of private gardens of several houses in downtown Ithaca, and there was no mention of fish in the advertising for the event.
This particular garden looked like many of the others, in that there were lush plants at every turn, carefully arranged behind stone paths. But once we stepped into a small greenhouse near the garage, it became clear that there was something else going on. Plants were growing in flat trays of moving water, which was coming from a giant tank full of fish all swimming in a circle. The man responsible for this explained that the nutrient-rich wastewater from the fish tank went to feed the plants, which in turn purified the water before it was recirculated throughout his garden and eventually back into the fish tank. In addition to harvesting vegetables and cut flowers from his tiny 0.1 acre lot, he and his family were also eating fresh tilapia several times a week…all for almost no cost! I was amazed that such an innovative system used inexpensive materials and took minimal time to maintain.
Agriculture Got 99 Problems…
More and more aquaculture systems are starting to pop up around the world, and people are beginning to realize the practical sense in creating more sustainable and locally-based food systems. Traditional agriculture, which for the purposes of this discussion I’ll define as growing plants outside, in soil, and in the ground, is running into a multitude of problems – and they’re only growing. And since as a society we are dependent on agriculture for our survival, problems for agriculture means problems for all of us. For starters, there’s the issue of population. There are currently around seven and a half billion people on the planet, and by 2050 the human population is projected to increase to almost 10 billion. Considering the fact that humans have been around for over 100 thousand years yet only reached a population of 1 billion just two hundred years ago, this accelerated population growth has led to an increased strain on natural resources such as water, soil, and nutrients, not to mention significant decreases in biodiversity due to habitat loss.
Looking forward to 2050, food supply demands are projected to increase by nearly 50%. According to some estimates, more than two-thirds of people will live in urban areas by 2050, which makes for the additional complication of having to preserve, transport, and distribute food. Water resources are becoming increasingly scarce, and rainfall is both less frequent and less predictable with climate change. Modern agricultural techniques are steadily degrading soils while also causing nutrient runoff issues in water bodies. At the same time, the essential plant nutrient of phosphorus is being added to these degraded soils in chemical fertilizer mixes, but is also a limited resource that could run out in as little as 35 years. To top it all off, monoculture crops experience high pest pressure, and widespread pesticide use is not only damaging to human and environmental health, but also is increasingly ineffective as pests evolve to withstand pesticide pressure.
The bottom line:
While traditional agriculture faces plenty of problems, it’s still by and large a cheap way to produce food for the world and is the reason we’re all eating today. That said, alternative methods of agriculture are growing in popularity, especially where traditional agriculture is limited because of water or space shortages. Aquaponics has been touted as the future of agriculture because it closes the loop between animal and vegetable agriculture by mimicking the natural world.
Aquaculture + Hydroponics = Aquaponics
So how does aquaponics really work? Aquaponics combines the two different systems of aquaculture and hydroponics into one so that the problems of each disappear. Aquaculture is the practice of raising fish for food production, either in a tank or in a cage within the open ocean. In either scenario, the amount of fish being raised in one place is so numerous that ammonia and other fish wastes quickly build to toxic levels if the water isn’t replaced, as much as 20% of the tank volume a day. Because aquaculture systems focus solely on fish, this nutrient-rich water is simply disposed of. In some cases, this water is simply dumped into creeks or rivers. Hydroponics can have some challenges as well. The idea of growing plants without soil has been around since ancient times, and when this came back onto our civilization’s radar one-hundred years ago, it was widely regarded as an ideal way to grow plants. However, hydroponics requires a continuous addition of nutrients to the water, which typically is purchased as a chemical mix. There are also issues of water waste, and disease issues like root rot and mildew.
Enter aquaponics, where the nutrient-rich water from raising fish goes into a soilless plant system in which nitrifying bacteria convert the nutrients from fish manure, leftover fish food, and algae, to a form that is more easily taken up by plants. The plants take up the nutrients and are able to grow better. The water is then recirculated back into the fish tank by means of a pump. In this system, the main inputs are fish food, electricity for the recirculating pump, and a little bit of water to make up for evaporation and transpiration. The outputs are fish and fresh vegetables for human consumption. Plants such as lettuce, spinach, herbs, can be easily grown, and in really nutrient rich systems with lots of fish, fruiting vegetables like tomatoes and cucumbers can also have success. Depending on the system, plants grow in trays that are flooded with the nutrient-rich water, or they’ll actually grow in a little floating “boat”!
In comparison to aquaculture and hydroponics, aquaponics uses far less water, and nutrients that are wasted in aquaculture are reclaimed by plants, by way of beneficial bacteria. Rather than feed both fish and plants separately, only fish food is added to the system but the plants still get the nutrients they need. The major issue of root rot that is seen in hydroponics is not an issue in aquaponics, most likely because of the symbiosis between plants and beneficial bacteria outcompeting fungal and bacterial pests. Compared to traditional agriculture, crops grow quickly and in smaller spaces, with overall fewer pest and weed issues from eliminating soil and having a closed environment.
Aquaponics Around the World
Places with limited water especially have been exploring the advantages of aquaponics in order to maintain a local supply of fresh fish and produce while using 80 to 90% less water. Aquaponics is already being used around the world, from Australia to Saudi Arabia to the United States. It’s already popular in Australia, where water scarcity has been an increasing problem and will only worsen with time. In Saudi Arabia, water is already an expensive commodity and the demand for fresh fish is growing. This combination is leading the way to an aquaponics industry. A group of researchers were able to build a system that recycled 98% of the water and produced more fish than traditional aquaculture, while getting the added benefit of growing lettuce, an attractive model in an arid country. In the United States, aquaponics is appearing in backyards and basements, with university research helping to develop systems and troubleshoot problems.
Aquaponics is one way to help feed the world, especially in climates where water is limited. Because the system is relatively compact and can be carefully optimized for production efficiency, it does well close to urban centers regardless of what the external environment may be like. Of course, managing an aquaponics system can take some work. Nutrient levels and the pH and temperature of the water need to be monitored for optimal fish and plant health. Figuring out how many fish and plants are exactly needed in the system can take time, and variables such as fish feed, species of fish and plants, and harvest schedule all play into the balance. But by integrating plants and fish into a single system, water is conserved, nutrients are recycled, two different food products are produced, and total operating costs are lower than if the two systems were separated.
The pressure to use more efficient and sustainable food systems will only increase, and so will using self-contained and weather-independent growing environments such as aquaponics. In addition to being practical, it’s fun! Aquaponics is a tiny microcosm of nature that can be small enough to fit inside any apartment or office window. In the near term, having a floating tray of fresh lettuce growing in symbiosis with a pet fish seems pretty ideal to me, and down the road, it’d be great to see every community maintaining aquaponics systems alongside gardens to meet some of their own food needs.