Plastics play a vital role in agriculture including aquaculture as it is ubiquitous, long lasting, easy to fabricate, easy to manufacture, user friendly, highly chemical resistant, UV resistant, corrosion-resistant, fatigue resistant, floatable, flexible and yields high strength. This paper reviews the use of different plastic materials in different components of aquaponics / hydroponics systems.
In aquaponics different grow beds/media are used for plantation. The grow beds are usually made up of HDPE (High density poly ethylene) and PP (Poly propylene) as they are inert, resistant to breakdown in water and most importantly food safe. One can prefer FRPs (Fibre reinforced plastics), where customizable media beds are required. In Nutrient Film Technique (NFT), circulation of water is from fish tanks to hydroponic tanks via. biofilter, sumps and pipes. The fish and hydroponic tanks are mostly made up of FRP. The fish tanks can be both circular and rectangular depending upon the capacity and type of fish to be reared. However, tanks made up of with HDPE and LLDPE (Linear low-density polyethylene) for mechanical strength, PP for impact resistance and performance in cold environment, PVC (Polyvinyl chloride) for rigidity are preferred. The hydroponics tanks are usually rectangular. Unlike concrete tanks these plastic tanks are easily customizable and portable, corrosion resistant and do not leach chemicals. The sump is made up of HDPE, because of its durability, food safe and UV resistant properties. FRP made up of epoxy/ polyester/ resin can be used where aquaponics is dealt upon a wider scale as it is lightweight, customizable, smooth, strong and has commendable durability. The biofilters are made up of HDPE for its highly UV resistant property, LLDPE for impact resistant and FRPs for customisability and durability. In case of small-scale production HDPE is preferred over other two and in case of large-scale production FRPs are preferred. Now a days the preferred biofilter media is also plastic-based, made either from PP, HDPE or PVC. In Moving Bed Biofilm Reactor (MBBR), PP is used, K1/K3 media, as it provides excellent surface area for biofilm. Sometimes PVC is used for moving bed biofilters. The bio-balls or plastic rings are made up of PP / HDPE / PVC. The pipes used in aquaponics must be of food safe, nontoxic, and durable as they carry nutrients and fertilizers. For the main supply of water, PVC pipes are used as they are strong, rigid and mostly inexpensive. HDPE pipes are used for underground lining. PEX (Cross-linked polyethylene) is used in smaller lines and drip irrigation systems as they are resistant to high temperatures. PP pipes are used where the pressure to be exerted is very high as they are durable. PVC pipes are preferred over HDPE pipes for cost effectiveness and easy usage. In Deep Water Culture / Raft aquaponics Expanded Polystyrene (EPS) and Polyeurethane (PU) providing buoyancy, inexpensiveness and lightweight are used for making rafts for holding net pots. The net pots are made up of PP, HDPE, PS or PVC. Net pots need to be lightweight, reusable, water safe and food safe, so PP and HDPE are mostly preferred over PS and PVC.
Overall we can say plastics not only serve as a solution to aquaponics/hydroponics, but also remain indispensable.
Keywords: Plastics, DWC, NFT, Biofilter, Food safe, Raft aquaponics.