Multi-species Green RAS

Multi-Species Green Zero-water exchange Recirculating Aquaculture System (MSG-RAS)

Land scarcity in many parts of the world is a problem especially in places like Singapore. Singapore is situated near the equator and is a typical tropical climate where large temperature fluctuation is rare (Meteorological Service Singapore, 2020). In general, a recirculating aquaculture system (RAS) would mean that high infrastructure and production cost would be incurred compared to other traditional systems. Where different systems are often compared, increasing the biomass in RAS system is one of the ways to earn back and offset the higher capital investment costs. This refers to increasing carrying capacity. In a super intensive culture of whiteleg shrimp L. vannamei, providing an optimal culture environment by providing sufficient nutrients to ensure high growth rates can be achieved. The challenge to increasing carrying capacity are due to pressure of environmental dynamics like environmental and biological pressure upon the cultured environment.

Being one of the most popular cultured shrimp species, L. vannamei, has led India to become one of the biggest producers in the world (Suresh, 2020). Range of researches regarding stocking and performance indicators or even diseases in various system have been discussed amongst academics and researchers. To improve food security that are obtained from sustainable aquaculture, Blue Aqua Breeding Centre located in Singapore has developed this method of aquaculture that utilizes a circular economy concept where minimal waste is produced during the on-going duration of the cultured period.

Multi-species Green zero-waste Recirculating Aquaculture System (MSG-RAS) (Patent Pending)

A super-intensive method of aquaculture for the growth and harvesting of two or more farmed organisms. This method of aquaculture utilizes the principles of the MixotrophicTM method of aquaculture patented by inventor Shishehchian, F. (2012), where phytoplankton, zooplanktons and bacteria are manipulated to achieve a desirable condition suitable for aquaculture.

This method of aquaculture provides the cultivation of one or more farmed organisms, where feed is required only for the first farmed organism, and the other organisms farmed can utilize and benefit from the nutrients in the waste effluent discharged from the first farmed organism. The water effluent from the first farmed organism is periodically replaced from the one or more farming vessels which have been filter fed or utilized from the former, thus reducing the amount of waste present during circulation while making sure waste reduction is done at a lower cost compared to a traditional RAS system.

Lower capital investment

High capital cost of setting up a RAS system are usually expected for the benefits it brings over traditional outdoor farming. This method of aquaculture can be performed in a greenhouse rather than a building which significantly reduces capital investment cost. The greenhouse also traps temperature where it is a well-known water parameter to promote faster growth rate. In addition, the greenhouse also provides as a shelter from the external environmental and predation.

Shrimp Raceway within a Greenhouse (Photo: Blue Aqua International, 2020)

Reduction in variable costs

This method of aquaculture utilizes green water instead of clear water. Green water consists of phytoplankton, zooplankton and bacteria which brings multiple benefits compared to clear water. Being a zero-water exchange system, the water used in this system provides natural food for the cultured shrimps in all live stages of the shrimp where feed is often 50% of the overall production costs in many reported systems (Partos, L. 2010). This also decreases FCR where it is an important performance indication used in Aquaculture.

Waste generation reduced significantly

Due to the multiple species present in this method of aquaculture, waste generation are reduced as waste from the higher trophic species serves as food for the lower trophic organisms. After facilitating effluent flow into the bioremediation ponds which may contain a second farmed organisms, bivalves could be added to reduce the micro-suspended solids present in the system as well as seaweed to reduce the soluble waste like the dissolved nitrogenous and phosphorus waste present in the system.

Seagrapes tanks incorporated into the system (Photo: Blue Aqua International, 2020)

The use of heterotrophic bacteria similar in Biofloc Technologies (BFT) systems helps to break down organic matter produced from the shrimps fecal and uneaten feed. The energy source of these heterotrophic bacteria is organic carbon, which there is an abundance of organic matter present in the system due to super-intensification.

Lower amount of energy consumption

Due to work done by the heterotrophic bacteria and the multiple species present in the system, lesser reliance is placed on external filtration. In the early stages of culture where shrimp requires less feed and generates less waste, the overall waste generation is insignificant and does not require external mechanical and biological filtration. Heterotrophic bacteria can digest the organic matter produced where nitrogenous waste are directly taken up by phytoplankton as food. Also, effluent from shrimp raceways does not require external energy and can be operated by a valve to flush out leftover faecal and organic matter produced by the shrimps. Effluent flows into the bioremediation ponds from the raceways where this directly lowers the amount of energy consumed as effluent flow to these ponds does not require external inputs of energy. By separating the raceways and the ponds, this ensures shrimps in the raceways can reach a higher density compared to polyculture.

Multiple effluent pipes into the bioremediation ponds containing bioremediatory species. (Photo: Blue Aqua International, 2020)

Lowers carbon footprint

This method of aquaculture mimics the natural food pyramid whereby the synergistic interactions of each trophic levels helps to reduce carbon footprint and multiple costs associated during methods of production. In addition, in lowering the energy consumption and waste generation, carbon footprint would be reduced during method of aquaculture.

Species diversification

Lastly, the purpose of species diversification or the bioremediatory species in the bioremediation pond was to remove waste effectively. They act as a biological filter in place of actual biological filtration equipment’s. However, the bioremediatory species provides bioeconomic value and could be sold when they reach marketable sizes or ready for harvest. Some exemplary species include may include species like Tilapia, Jade Perch, bivalves like clams, mussels, some other Molluscs. For seaweed, seagrapes can be included into the system as shown above. By creating a circular economy and making use of all the available resources in this method, Blue Aqua International Pte Ltd is driven and strives continuously to achieve circular economy and the movement of sustainable production in aquaculture

Illustration of a circular economy (Photo: Blue Aqua International, 2020)

Meteorological Service Singapore (2020). Climate of Singapore. Retrieved from
http://www.weather.gov.sg/climate-climate-of-singapore/

Partos, L. (2010). FAO: Fish feed costs to remain high. Retrieved from
https://www.seafoodsource.com/news/aquaculture/fao-fish-feed-costs-to-remain-high

Shishehchian, F. (2012) WO2013191642A1. Mixotrophic method of aquaculture. WIPO PCT.
Suresh, A.V. (2020). How India became the world’s top shrimp producer. Retrieved from
https://www.aquaculturealliance.org/advocate/how-india-became-the-worlds-top-shrimp-producer/

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