Source material

Overview

1. 1.1 Definition

   Original publication 2021 · First published on FarmHub Learn 2021-04-22 · Kentucky State University

   Aquaponics (AP) is a self-supporting food production system that combines recirculating aquaculture with plant culture in the absence of soil (hydroponics). High-volume fish production results in nutrient- rich water that can be used to provide nutrients for plant cultivation.

   Source: Janelle Hager, Leigh Ann Bright, Josh Dusci, James Tidwell. 2021. Kentucky State University. Aquaponics Production Manual: A Practical Handbook for Growers.

2. 1.2 Context

   Original publication 2021 · First published on FarmHub Learn 2021-04-22 · Kentucky State University

   Development of aquaponic systems resulted from the need to reduce costs associated with high-nutrient effluent discharged from recirculating aquaculture systems (RAS). Known for intensive aquaculture, RAS can produce large quantities of fish in a small volume of water. Some water is discharged and replaced in the system over time, as solid waste and toxic nitrogen by-products (ammonia (NH3-N), nitrite (NO2-N), and nitrate (NO3-N)) build up. Concentrated discharge from intensive aquaculture is a barrier to positive consumer perception of aquaculture. However, these accumulated nutrients can be similar in composition and concentration to hydroponic nutrient solutions and often exist in the form preferred by plants (Rackocy et al. 2006). Combining these two production technologies provides an efficient and sustainable method of growing fish and produce.

   Source: Janelle Hager, Leigh Ann Bright, Josh Dusci, James Tidwell. 2021. Kentucky State University. Aquaponics Production Manual: A Practical Handbook for Growers.

3. 1.3 Importance

   Original publication 2021 · First published on FarmHub Learn 2021-04-22 · Kentucky State University

   Hydroponics and intensive RAS each have ecological and economical drawbacks when considered individually. Hydroponic crops rely on chemical fertilizers that are expensive, hard to source, and in some cases are derived from rapidly disappearing natural resources. In intensive fish production, concentrated wastes are generated (i.e. effluent) that require expensive treatment methods, leading to poor consumer perception regarding environmental impacts. The high initial investment may be prohibitive to potential producers, as well. Aquaponics provides the opportunity to utilize aquaculture effluent while growing plants with a sustainable, cost-effective, and non-chemical nutrient source.

   The integration of fish culture and plant production can provide several opportunities for farmers or producers, including sustainable agriculture, marketing versatility, and generation of multiple income streams. Environmentally, plant growth and yield in aquaponics can meet, or in some cases surpass, output values of either hydroponics or soil-based agriculture (Pantanella et al. 2011, Savidov et al. 2005). The shared core concepts of efficient water and land use, the ability to intensify crop production year round, and use in geographic areas not suitable for traditional agriculture has driven a recent increase in the popularity of aquaponics (Somerville et al. 2014).

   While production values have been shown to be similar to both hydroponics and RAS (Pantanella 2013, Savidov et al. 2005), the integration of these systems can make it more difficult to manage. Many groups interested in aquaponic production are deterred by the high start-up cost and lack of proven models for success. Understanding that aquaponics is a complete ecosystem is essential to provide correct conditions for fish, plants, and bacteria, which are the three major groups of organisms that drive AP systems.

   Source: Janelle Hager, Leigh Ann Bright, Josh Dusci, James Tidwell. 2021. Kentucky State University. Aquaponics Production Manual: A Practical Handbook for Growers.

4. 1.4 System Types

   Original publication 2021 · First published on FarmHub Learn 2021-04-22 · Kentucky State University

   There are two main types of AP systems, coupled and decoupled. The coupled approach is widely used and is based on feeding the system known nutrient-input amounts/values. The support for plant growth and bacterial consumption (in the biofilter) typically come from commercial fish food and must be factored into system input requirements. These ratios are used to ensure that toxic waste products from fish effluent do not build up (due to an insufficient biofilter), excess nitrates do not occur (from not enough plants), and nitrate deficiencies do not develop (from an excess of plants). Recommended operating ratios for aquaponic systems will be covered in the Structure and Design section.

   Given the wide range of growing conditions among fish, plants, and bacteria, coupled systems do not operate at the optimum values for either fish or plants. The ideal nutrient environment for fish would usually be nutritionally inadequate for most plants, and an ideal nutrient level for plants would be toxic to most fish. For this reason, decoupled systems are being explored, though their use is not widespread. In a decoupled aquaponic system, the RAS and hydroponic components are joined but operate as separate systems that can be controlled independently (Goddek et al. 2016, Pantanella 2013). Typically, water that feeds the hydroponic system does not enter back into the fish culture tanks after being filtered by the plants. Instead, water lost though transpiration and evaporation in the hydroponic unit is replaced with water from the RAS, which in turn is replaced with new water (Kloas et al. 2015). This setup offers greater control over the individual system and allows each to be operated at their optimal range. Disease treatment and nutrient deficiencies (or toxicities) are more easily managed, as well. Decoupled systems are not as well researched as coupled systems and require producers to have a higher level of expertise in hydroponics, plant nutrient management, and aquaculture system design.

   Source: Janelle Hager, Leigh Ann Bright, Josh Dusci, James Tidwell. 2021. Kentucky State University. Aquaponics Production Manual: A Practical Handbook for Growers.

5. The Big Picture

   Original publication 2021 · First published on FarmHub Learn 2021-04-22 · Kentucky State University

   The world population is an estimated 7.7 billion and is expected to reach 10 billion by 2050. To feed this expanding global populace, food production must increase by 30-50%. This increase would require that land used to raise crops expand by almost 1.5 billion acres; that is about ¾ the size of the continental United States.

   In 2020, agriculture utilized almost 50% of the world's vegetated land. The ongoing increase in atmospheric CO2 levels, leading to increased global warming, would be exacerbated by the large-scale conversion of forested lands to crop land necessary for food production. In addition, current agriculture production accounts for 90% of all water used by humankind. This growth and consumption of resources is not sustainable. Alternative ways to increase food production are required; we simply cannot just do more of what we are doing now.

   The World Resources Institute (WRI) recently published a report titled "Creating a Sustainable Food Future" (Searchinger et al. 2014). The authors propose five "courses" or ways to produce more food without increasing environmental impacts. Aquaponics is a concept that addresses several of these initiatives.

   One of the WRI courses is to increase food production without expanding agricultural land. To accomplish this, they state that "increased efficiency of natural resource use is the single most important step toward meeting both food production and environmental goals." As opposed to most recommendations, they propose increasing production intensity as a pathway to sustainability. Aquaponics is one of the more efficient and intensive food producing systems available. It is efficient in terms of the amount of food produced per unit area, unit of water, and unit of nutrients added to the system, especially in tropical or sub-tropical climates where heating costs are minimized.

   Another solution proposed in the report is to increase fish supply. There is an indication that fish consumption is predicted to rise 58% by 2050 (Searchinger et al. 2014). However, the WRI study assumes that production from capture fisheries will actually decrease 10% during the same period. To meet consumption demand, aquaculture will need to at least double output. However, that would add to land use issues through the construction of 50 million acres of new production ponds. The authors pose that aquaculture must also become more land-efficient and that water recirculation technologies could help intensify production, reduce land use, and provide better pollution control.

   Aquaponic production is a promising model for resource reuse and efficiency; this along with other regenerative agricultural techniques can have local impacts on many of these pressing problems and serve as a model for future technologies and developments.

   Source: Janelle Hager, Leigh Ann Bright, Josh Dusci, James Tidwell. 2021. Kentucky State University. Aquaponics Production Manual: A Practical Handbook for Growers.