Macau Matters | Aquaponics

Richard Whitfield

Aquaponics is the combination of aquaculture for growing fish and hydroponics for growing plants that is often used in old factory buildings in cities. It is something to consider for Macau to use up old factory spaces and help to diversify the economy.
When I was a postgraduate student in the 1980s I spent many hours in the library poring through printed indices of journal articles, then completing inter-library loan forms to get copies of the articles I was interested in, and waiting weeks for the copies to arrive. It was a very long winded process that is now totally obsolete. Just do a simple google.com or youtube.com search for aquaponics and you can find out more than you ever want to know about this interesting technology in just a few hours. The growth and evolution of the Internet in the last 40 years has totally changed learning.
I really like highly efficient sophisticated systems where the waste output from one process is transformed into the input for another, and aquaculture is a very good example of this in practice. It is a cycle which can start anywhere, but let us start with the fish for convenience.
They are fed with meal made from ground up vegetable and protein and once grown can be harvested for human consumption. The waste from the fish tanks consists of particulates and ammonia (in the water). The particulates (uneaten fish meal and faeces) is eliminated from the system, to be used as a good traditional garden fertiliser. By contrast, the ammoniated water is pumped to a bio-filter where common bacteria and algae convert the ammonia to nitrites and nitrates, which are excellent plant foods. This nitrogen rich water is then used to grow plants without soil – most plants can be grown in inert pebble beds filled with flowing nitrogen rich water. After being used by the plants, the water can be returned to the fish tank for re-use. The fully grown plants can be harvested for human consumption. Finally, leftover vegetables can be composted with worms to be made into fish meal, thus starting the cycle again.
If this kind of system is well designed and tuned very few (if any) additional chemicals are needed so that aquaculture can be considered a form of organic farming. Even the water is used in a closed loop!
In Macau we have a lot of leftover food that can be readily processed to make fish food (or conventional garden fertilizer). When used with an aquaponics “factory”, the fish meal can be utilized to grow high quality fish and plants for human consumption. These aquaponics factories can be set up in obsolete factory buildings in Macau.
Natural sunlight is also not an issue because artificial lighting is often used in this kind of system. In this way the plants can be exposed to 20+ hours of “daylight” each day to speed up their growing cycle. Moreover, photovoltaic panels combined with batteries can be used to renewably generate the electrical power needed for the artificial lighting (and to run the water pumping subsystems).
Thus, the main inputs to the system are low quality disused factory space, low value leftover waste food and free sunlight and the outputs are high quality “organic” fish and plants ready for eating and traditional garden fertilizer. Don’t you love this kind of efficiency?
And I am sure it would work in Macau, like it does in many cities in the developed world and in developing countries like Thailand, the Philippines and China.