We often seen the word sustainability used in conjunction with aquaponics but just how sustainable is it?
Water use efficiency and the absence of herbicides and pesticides are powerful arguments in support of sustainability…..and so is the conversion of fish wastes into plant food.
But these are only part of the picture.
Any notion of sustainability has to acknowledge the following:
The use of wild catch fishmeal in the manufacture of fish rations.
The cost of the energy required to run the pumps and environmental control systems.
The amount of energy embodied in the components used to build any aquaponics system
Most aquaponics systems rely on pelleted rations largely made from fishmeal. It can hardly be claimed that aquaponics is sustainable as long as it depends on rapidly declining fish stocks for its core ration ingredient.
While there has beeen some work done on alternative feedstuff for freshwater fish, there’s much more to be done before aquaculture (and aquaponics) can cut the fishmeal umbilical.
The operators of most small aquaponics systems would struggle to quantify their energy costs. If the cost of the energy that it takes to grow fish and plants exceeds the value of the fish and plants, then it could hardly be described as sustainable…….financially or environmentally.
Currently, many aquaponics systems are made from plastic or fibreglass components. These components are relatively expensive which raises the question of return on investment. How much clean fresh food does one need to produce to cover the cost of the production system? How long does it take to recover the cost of your investment?
The other issue is that the plastics and fibreglass industries are largely reliant on the oil industry for their feedstocks. How can something be sustainable as long as it depends so heavily on declining oil stocks?
OK……so while aquaponics is more efficient in its use of water compared to soil-based gardening systems, it certainly doesn’t stack up so well in other areas of sustainability.
So, what’s the answer?
Aquaponics (like all intensive farming systems) is largely dependent upon the energy provided by fossil fuel so designing systems to minimise energy use is a logical place to start.
Minimising how far and how high you pump water is one way of reducing energy costs. Selecting system components for their energy efficiency is another way.
Most aquaculture species require supplementary heat for year round production. The use of passive solar heating and insulation to reduce heat loss are central to reduced energy consumption.
While plastics and fibreglass lend themselves very well to aquaponics, perhaps their application should be limited to those system components which demand their use. The biggest user of plastics and fibreglass is growing systems.
Using a broader range of growing systems – including some which are soil-based – is one way of reducing the use of composites. Building growing structures out of plantation timber (lined with plastic) is another way.
Finding alternative feedstuffs for fish is essential if aquaponics is going to have a long term future. The answer to this problem is the inclusion of more organisms into the integration.
Don’t get me wrong. I think aquaponics is great.
Its water use efficiency and the symbiotic relationship between fish and plants entitles it to kudos from the outset.
Its current dependence on fossil fuel energy and fish-based diets, however, makes aquaponics (in a sustainability context) a work in progress.