What are the differences between recirculating farms, hydroponics and aquaponics? And what are their environmental benefits?
Published: 10/08/18, Last updated: 2/28/24
Hydroponic and aquaponic farms are land-based systems that use recirculated, nutrient-rich water instead of soil to grow food, flowers and sometimes fish.1 Hydroponic systems grow vegetables, herbs, some fruits and flowers in growth mediums such as coconut fibers or perlite. Aquaponic systems incorporate fish, which provide natural fertilizer and can also be harvested as food.
Recirculating farms are closed-loop, land-based systems that use constantly-cleaned water to raise fish and grow food. There are three main categories of recirculating farms: land-based recirculating fish farms, crop-producing hydroponic and aeroponic systems, and aquaponic systems that support both fish and crops.
Recirculating fish farms raise fish in tanks that have a water filter system to clean the water for constant reuse, just like an aquarium at home. Recirculating systems can be very small, supporting just a few fish, or very large facilities that can support production of active species like salmon and trout. The environmental impacts of these operations vary based on their size, inputs and design, but can be an efficient way to raise fish with minimal outflow of pollutants to the environment.
Hydroponic systems grow plants in nutrient-rich liquid, without what is traditionally thought of as soil. Without soil and its mix of minerals and organic matter to supply vital plant nutrients, hydroponic systems rely on nutrients that are added directly to the water instead. These can come from organic sources, like compost-based liquid teas, or from fertilizers that rely on synthetic nitrogen and other inorganically derived nutrients. In a hydroponic farm, plants grow directly in the liquid, while in an aeroponic system, plant roots grow in humid air and are periodically sprayed with nutrients and liquid. Some hydroponic farms use sand or gravel beds to support the plants as they grow, while aeroponic setups often use perforated pipes to support growing crops.
Hydroponic and aeroponic farmers can grow many of the same things that are grown in traditional soil-based farms, including herbs, fruits and vegetables. Hydroponics are especially common for fresh produce like lettuce, tomatoes, strawberries and cucumbers, which adapt easily to soil-free conditions and thrive in greenhouse conditions.
Aquaponics farms are a combination of aquaculture and hydroponics — where fish are raised in tanks and the water from the fish tanks is recirculated into the plant beds, so the plants can absorb nutrients from fish waste in the water, cutting back on the need for added fertilizers. When the water is returned from the plant beds to the fish tanks, it is cleaned of waste.
Hydroponics and aquaponics are not new concepts. Evidence of such systems dates to early civilizations, such as the Maya and Aztecs.2 In those systems, fish were typically raised in outdoor ponds; but over the last four decades, these farming systems have been brought indoors, allowing for a more controlled environment. In the 1970s, researchers began adding plants to these systems as a means of cleaning the wastes produced by fish. A University of California Berkeley scientist brought hydroponics into the modern era with a commercial tomato system he established in California in the early 1900s.3
Hydroponic and aquaponic systems are incredibly versatile and can easily adapt to growing crops that might have a hard time growing together in a less controlled system. They are productive, produce little waste and require minimal inputs after the systems are established.
The systems don’t have to be complex; they can often be built with supplies from hardware stores and scaled up over time as space allows. Because they don’t follow a rigid design, they can be built inside or outside into odd-shaped or unusual spaces like backyards, basements or warehouses. The scale varies from small, personal use beds and tanks all the way through large, commercial-scale systems. They can be established in urban and rural spaces, where they can become a source of fresh, local food.
Hydroponic farming often outperforms soil-based farming in terms of the number of harvests of products per growing season because when environmental conditions are controlled, year-round growth is possible. Some hydroponic systems have as many as 12 crop rotations per year.4 5
This is also true for aquaponics in many cases. For example, some aquaponics systems can produce market-sized fish in just nine months. In addition, farmers can switch crops as necessary to meet demand — even out-of-season demand.
Hydroponic systems can be stacked and grown vertically which means they don’t require large tracts of land.6 Because they don’t require soil, they can be established in places where the soil is not suitable for farming.
Well-designed systems can also be very water efficient. Once the initial water needs (which are variable and depend on the size of the system) are met, the amount of make-up water required is minimal, because water is circulated throughout the system and is reused. Some systems use as little as 10 to 15 percent of the water required by land-based farming.7
The location and specific set up of a recirculating farm has a big impact on its energy needs; however, these systems can be efficient. Hydroponic systems established outdoors don’t require artificial lighting, and for those that are inside, energy needs can be minimized using efficient forms of lighting and solar energy. Aquaponics systems that match the type of fish to the region — for example, tropical fish in warmer regions — do not have the added expense of heating the water in cooler weather.8
Because the systems aim to be “closed loop” — reusing waste flows to minimize inputs and outflows — there is little to no waste and no run-off generated in well-designed hydroponic systems.9 Hydroponic systems require little to no pesticides or herbicides, and fertilizer use can be tailored to the system. Because the water is recirculated, there is no way for waste products to reach local waterways.
In aquaponics systems, no pesticides or herbicides are used because their use would kill the fish. Waste from the fish is used as a fertilizer for the plants. Solid waste that comes from the fish waste is often collected and used as compost.
Systems established in community spaces offer workers an opportunity to provide job training to volunteers. The plants, fish and facilities must be maintained, offering volunteers the opportunity to learn job skills. In larger operations, there is enough labor required to create jobs. Because the systems can operate all year long, recirculating farms can create more permanent jobs than standard agricultural work, which is highly seasonal.10
Because hydroponic and aquaponics systems can be established anywhere — from tight urban spaces to remote rural places — once they are established, they can be a source of local produce and/or fish that can help reduce food insecurity.11
Systems that are established at a scale larger than personal use can provide local sources of fish and produce to the community. The goods can be sold directly to consumers on site or at farmers’ markets, or can be delivered through CSAs.12
Low resource requirements can make the systems easy to establish as a means of local food production that can help communities recover after disasters. In addition, their designs make them less vulnerable to extreme weather conditions like heat, droughts and floods. For example, systems established indoors are not vulnerable to weather changes.
While well-designed and appropriately scaled recirculating systems can be an efficient way to produce some food, they aren’t a perfect answer for all crops. Many systems have high energy use that limits their potential, and poor design can hamper efficiency and impede systems from achieving a tighter loop between inputs and waste.
Depending on how and where they are established, hydroponic and aquaponics systems can have high energy costs. This is because they incorporate lighting, pumping, air moderation and — where fish are included — possibly water heating and cooling.13
Energy costs associated with lighting used to be a significant part of hydroponic operating budgets but with advancements in efficient LED lighting, those costs have come down. The true costs of set up and operation will be determined by scale, location and whether the system is set up outdoors where it can take advantage of sunlight, or indoors where artificial lighting and air movement will be required.
For aquaponics systems established where the climate is not suited to the type of fish being grown — for example, growing tropical fish like tilapia in colder climates — water heating might be required, which could significantly increase energy costs.14 Additional energy requirements include water circulation via pumps.
Water requirements for hydroponics and aquaponics systems are generally low compared to land farming.15 Meeting the initial water requirements is generally not an issue, unless the system is located in a water-stressed environment or there is not a ready source of water; for example, a system located in an empty city lot where there is no plumbing infrastructure in place and water must be obtained from offsite sources like fire hydrants. Once the initial water supply is in place, make-up water needs are generally minimal.
Depending on the type of fish raised in aquaponics farms, feed can present a challenge. Fish that are carnivorous are often given feed made up in part by small, wild fish taken from the sea, like menhaden.16 These fish are a primary food source for marine wildlife — dolphins, birds and larger fish — and are also critical to the diets of many coastal communities worldwide.17 Many aquaponics farmers raise fish (like tilapia) that can be fed a vegetarian diet; however, this type of feed often includes grains like soy and wheat and other commodity crops that are dependent on industrial farming practices. Many farmers find other, more sustainable sources of feed for their fish, such as duckweed or black fly larvae.18
Compared to traditional farming, hydroponic and aquaponics systems can have low start-up costs, primarily because large amounts of land are not required. But depending on the scale, system design and location, the initial and operating costs can be significant.
Initial costs include the cost of acquiring land/buildings or rent on those spaces, equipment like tanks, pumps, tubing/hoses and plant rafts, energy for lighting and heating, water (if a ready source does not exist, as might be the case in a rural location or in an abandoned urban lot), materials, plant starters, fish frying and building supplies.
Ongoing costs include labor, energy usage and fish feed for aquaponics. When all costs are considered, the bulk of the costs come from energy use and labor, and (depending on the set up), potentially, rent.19
Some enterprising companies are preassembling hydroponic kits in cargo containers and selling everything required to start a hydroponic farm just about anywhere, for a set price.20 The setup could be more challenging with the jump to aquaponics, as the addition of fish brings additional requirements for heating, fish feed and additional space.
Hydroponic farms have capitalized on inexpensive labor, land and energy in regions like Appalachia, where their relative proximity to large cities makes shipping produce relatively easy. However, as these farms become more profitable, some community members have voiced concern that the increase of automation in large facilities could quickly make some of the jobs they create obsolete.21
Both hydroponic and aquaponics farms are receiving a lot of attention in the media which is helping to build their success. There is growing interest from venture capitalists to establish large-scale systems, primarily in hydroponics. Guides that explain typical start-up costs indicate that hydroponic farms can become profitable quickly depending on the set up.22 Aquaponics systems that have strong educational components and are run as nonprofits tend to do better than commercial aquaponics ventures.23 There are fewer commercially successful aquaponics farms than there are hydroponic farms around the country.
Some studies have compared the profitability of aquaponics farms to that of small land-based farms and found they tend to be similar in size and gross sales revenue. They also found, similarly, that aquaponics farmers often must take off-farm work to earn a viable income.24 This is true for many small farmers in that much of their household income stems from off-farm activities.25
Research suggests that, like other small farms, aquaponics farms tend to be more profitable if farms diversify their revenue stream, for example, by selling non-food products and aquaponics-related services, or conducting educational trainings.26 The EPA has produced a start-up guide to help potential aquaponics farmers create a viable business plan.27
While some hydroponic and aquaponics producers have received organic certification, there has been a debate over whether crops grown without soil can be included within the scope of organic production. Given the organic label’s focus on improving soil quality, some land-based farmers have argued soil-free methods don’t qualify. However, the National Organic Standards Board recently voted not to exclude hydroponic and aquaponics farms from organic certification.28
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