Ideal form of circular agriculture? What are the challenges for the popularization of "Aquaponics" | Newswitch by Nikkan Kogyo Shimbun
A new farming method called "aquaponics" that combines agriculture and land-based aquaculture on the same land is gaining attention. In the agriculture and livestock industries, it is effectively used as a fertilizer for agricultural crops and as a soil conditioner after composting as a method of treating livestock excrement. Similarly, aquaponics is an attempt to turn farmed fish waste into fertilizer for crops.
Aquaponics benefits both agriculture and aquaculture. From the point of view of agricultural production, much of the fertilizer (liquid fertilizer, etc.) that is normally purchased becomes unnecessary. In addition, from the perspective of aquaculture, there are benefits such as reduced water treatment costs. When conducting closed-type land-based aquaculture, it is necessary to continuously remove from the tank the harmful ammonia excreted by the fish being raised. In a closed-cycle land-based aquaculture system, nitrifying bacteria first convert ammonia into nitrite and then nitrate to attenuate it, and then the nitrate is removed by a denitrification device. Aquaponics, on the other hand, circulates water containing nitric acid, which is decomposed by nitrifying bacteria in the biofilter, through the hydroponics equipment so that the plants absorb the nitric acid as nutrients, and the purified water is returned to the fish tank. It is a system that goes back (Fig.). Aquaponics is a production system that balances productivity and environmental friendliness, and some experts point out that it is an ideal form of recycling-oriented agriculture.
In addition, small-scale and simple aquaponics kits for home and school education with a planter installed on the aquarium are also available on the market, and can be purchased for several thousand to tens of thousands of yen on the Internet or at home centers. It is possible to. However, the current situation is that aquaponics has not yet reached the stage of full-scale popularization. Technological development has made great strides in research-scale systems, but full-scale business-scale systems are still in the process of development, and some issues remain. First of all, the water used is circulated between the equipment for hydroponic cultivation of vegetables and the breeding tank for cultivating fish, so in principle, the fish that can be cultivated is limited to freshwater fish. On the other hand, in Japan, freshwater fish generally do not sell at high wholesale prices, and are less profitable than conventional land-based aquaculture (mainly high-grade fish raised in salt water, such as pufferfish, flounder, and grouper). Also, for hydroponic vegetables, the use of fertilizers and pesticides other than fish excrement is restricted so as not to adversely affect aquaculture. In addition, the plant factory requires meticulous water quality management according to the type of vegetables and fish that are grown in any type of land-based aquaculture. It should also be noted that the combination of vegetables and fish species must be selected. In this way, it can be said that it is necessary to carefully consider the profitability when considering the introduction.
At a time when interest in the SDGs is increasing and the impact of agriculture, forestry and fisheries on the environment is being scrutinized just like other industries, the concept of aquaponics itself is a promising future. It can be said that there is In the future, we look forward to the expansion of research, such as the expansion of targets to high unit price fish species, the establishment of combinations and cultivation techniques that improve the growth conditions and quality of both fish and vegetables.
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