Posts Tagged ‘ Bleiswijk ’

Issue 101: Aquaponics Revisited

July/August – 2008
Author: Mike Nichols

The author at the Bleiswijk project.

Aquaponic systems are being increasingly recognised as having potential for solving some of the many problems facing modern agriculture and aquaculture. MIKE NICHOLS profiles two very different commercial aquaponic systems that embrace new ideas and innovations.

Nick Savidov with basil crop and fish tanks in background.

I recently stopped off for a few days in Alberta, Canada, to meet up with Dr Nick Savidov, the Greenhouse Team Leader of the Crops Diversification Research Centre, Brooks, where I was briefed about their $15 million investment in state-of-the-art research greenhouses to be built in the next 12 months. I also learnt that he has greatly improved his aquaponic project with a few minor ‘tweaks’, which now make it significantly more productive and sustainable than the model developed by Jim Rekocy (US Virgin Islands) on which the original Brooks project was based.

Deep flow system showing aeration.

Nick has made more efficient use of expensive greenhouse floor space by joining all the beds into a single ‘pond’ by doing away with all the paths and discarding the aquarium stone bubblers and replacing them with air lines of PVC tubing with small holes.

View of root system of basil plants.

In the new facility, he has improved water, space, and labour efficiency and eliminated chemicals including pesticides, fertilisers and pH adjustments. A new component has been incorporated into the system called Biofloc based on Geotube® technology, which allows him to physically separate solid waste from water. The water is then returned back to the system instead of being pumped out with solids as in the previous model. Solids are allowed to stay in the system gradually releasing nutrients due to a bio-fermentation process and thus serving as a slow-release fertiliser. He has found that the solids removed from the water using GeoTube® technology and stored in the Geotube® tank have been degrading with increasing rate releasing additional nutrients to the system. The result is nutrient use efficiency close to 100%. In other words, for the first time, he has created a recirculating self-sustainable system, which allows the conversion of practically all the organic material (fish feed) input into food (fish and plant biomass).

Basil plants and fish tanks.

Bacteria are the key to the whole system, and it is interesting to note that according to Dr Savidov in year one the aquaponics system produces only 70% of the yield of a conventional hydroponic system, but in year two yields may be as much as 30-40% higher than those obtained using conventional hydroponics. He attributes the difference to micro-organisms in the system that take a year to develop the right balance.

Aquaponics in the Netherlands
In the Netherlands I visited the Greenhouse Improvement Centre at Bleiswijk primarily to meet with Willem Kemmers (of Priva), the Project Leader of EcoFutura (Fish and Tomato Project, another name for aquaponics) and with Pim Wilhelm, the fish biologist.

Fish and tomatoes – Bleiswijk, Netherlands.

The Fish and Tomato project is most impressive, and so it should be as it is supported by some major industry players. The fish tanks are held inside the greenhouse, below the hanging troughs in which the tomatoes are grown in Grodan rockwool. I have personal difficulties with the project, however, in terms that it is not a fully re-circulating system, and also the nutrient stream from the fish is sterilised with ultraviolet light before it is used on the tomatoes, and at the same time the solution is analysed, and the pH adjusted, and other nutrients added to suit the tomatoes. Similarly, many of the organic solids are removed and dumped. The drainage is then returned to the fish tanks, but is again modified (by increasing the pH) to suit the fish.

Thus, this is not the same as the fully re-circulating and sustainable system as has been developed in Alberta.

One of the difficulties of aquaponics is providing crops such as tomatoes with the optimum conductivity (about 3.5mS) necessary to ensure a high quality tomato in the middle of the winter. The conductivity of a solution coming directly from the fish phase is normally very low, but in a deep flow system this is not important as the nutrients flow past the roots, and the leafy crops are able to absorb adequate nutrients, however with tomatoes the objective is to use conductivity to control growth and fruit quality, and this is difficult (impossible) with a deep flow system using aquaponics.

However, when using a media-based hydroponic system such as rockwool or coir, it should be possible to control the conductivity of the solution by using reverse flow osmosis, and directing the water phase back to the fish, and the high conductivity stream to the plants.

Aquaponics is taking off in Canada as a teaching tool. A number of schools have now purchased Nick’s mini aquaponic set up, which he developed as a research tool. They are using this to demonstrate to school students some of the simple principles of ecology and biology.

Aquaponics vs organics
Sadly, the mainstream organic principals still do not like aquaponics. The argument is that it is unnatural, because the plants are not grown in the soil. A very strange decision when the system is certainly the most environmentally friendly and sustainable system that currently exists, as no nutrients are leached through the soil profile, and the system is particularly water efficient. Growing organically in soil is neither water nor nutrient efficient when compared to aquaponics!

In any case, how do you define soil? Basically it is:
• solid particles (e.g. sand, clay silt)
• organic matter
• micro-organisms
• water
• gases (oxygen, CO2 etc.).

An aquaponic system comprises all of these apart from solid particles, and these could be easily added to the system! The addition of a rock or two to the deep flow system should be more than adequate.

It is interesting to note that greenhouse soil-based organic systems usually produce only about 60% of the yield of a conventional hydroponic crop. In Canada, organic certification is available for crops grown using aquaponics, provided that they are grown in a cocopeat (coir) medium!

About the author
Dr Mike Nichols is a horticultural research scientist at the College of Sciences, Massey University, Palmerston North, New Zealand, and a regular contributor to PH&G.