GreenTech 2019: General Observations and an Aquaponics Presentation

It’s already a month ago I was at GreenTech 2019.

In the meantime, I’ve been busy working in a group of students on a consultancy project for a company. I signed a non-disclosure agreement, so I can’t say too much, but it involves mussels. Great filter feeders, welcome in any aquatic ecosystem.

Getting back on topic: a month ago I was at GreenTech for the first time since 2016.

GreenTech 2016 was the first time I met people from the Association for Vertical Farming in person – people like Zjef Van Acker. There I saw the AMI concept for the first time: banners explaining aquaculture, plant production, fungiculture, and insect rearing. Back then I was far more focused on the plant-production part of indoor agriculture, and vertical farming in particular. Seeing the AMI concept changed this – and now I’m almost more interested in the ecosystems aspect than the indoor aspect of agriculture.

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GreenTech 2019 was also interesting in that I met Nijat from Azerbaijan, a reader of this blog. Nijat has been travelling around the world looking for new technologies to apply in Azerbaijan, on behalf of the conglomerate Azersun Holding.

Nijat and me in Utrecht after GreenTech 2019.

There have definitely been some changes over these three years. Compared to 2016, there was a lot more related to vertical farming. Cannabis was also huge, with its own dedicated pavilion with plenty of talks. And although it’s not on the same level as AquaFarm/NovelFarm for this, I noticed there to be (a little) more about circularity and ecosystems.

Now for some proper substance – one of my favourite presentations at GreenTech 2019.


The Potential Opportunities of Aquaponics – Sara Crappé

Sara works for PCG (a provincial pilot farm in East Flanders).

The aquaponics project she shared started in 2009. Back then, their idea was to put the fish tanks under the plants. This would provide shading for the fish, and cooling and carbon dioxide for the plants – pretty clever. In practice, however, this led to fungal disease and tricky climate control.

Because of this, in 2015 they decided to separate the two systems more, with 9 fish tanks, and 9 rows of crops.

The fish they have been using is Omegabaars, producing about 150 tonnes per year. Omegabaars – a special kind of perch – has been in the media a lot in Belgium recently. What makes it so special?

– Omegabaars are efficient. They have a small head, which leads to better feed conversion – more energy going to the protein we eat (though bone broth is great stuff, but that’s another story).
– They are also herbivores. This means fishmeal isn’t required to feed them (they eat a secret mix of corn, algae, seeds, and minerals). It also means the fish excrete less sodium into the system, meaning less leaching is required and more nutrients can be conserved.


In 2017, PCG started a trial with tomatoes. Their goal was to compare hydroponics to high-density and low-density aquaponics.

The result was that aquaponics gave a similar yield to hydroponics!

But it’s not all sunshine and roses. The aquaponics plants suffered from blossom-end rot. This was due to there being more potassium (K) in the aquaponics system. This was easy to fix though, by replacing potassium-based fertilisers and buffers with calcium-based ones. They still have to add a bit of potassium in the beginning of the plant’s growth cycle, but afterwards, no more is required.

Then, a year later, they tried the same experiment with cucumbers. Their main finding there was that there was hardly any difference between the sodium content in the aquaponics system compared to the hydroponics system.

Currently, they are doing similar experiments with bell peppers.

Sara identified a few direct benefits of aquaponics, beyond the circularity and sustainability benefits known to most aquaponics enthusiasts:

– For the fish farmer, the benefits are being able to get rid of unwanted nutrient-rich water. It has also been useful to have access to greenhouse infrastructure, like the combined heat-power (CHP) installations most greenhouses have.
– For the vegetable grower, there aren’t that many benefits. Nutrients are currently not that expensive. However, the extra marketing from using aquaponics is a big plus. For the crops PCG looked at, there was no difference in taste or BRIX – sugar content – compared to hydroponics.

I must say, though, that their aquaponics system is decoupled. Decoupling has the benefit of providing more control. However, having an ecosystem of microbes in the root environment is extremely beneficial as well.

Sara and PCG haven’t looked at the effect of root-zone microbes yet – but insurance companies are interested in finding out how aquaponics systems stack up when it comes to robustness. Aquaponics systems are less predictable short-term, compared to hydroponics systems – but microbes’ ability to fend off pathogens may come in handy. They just need the research to back this up.

Despite this, there were two other people at GreenTech who had looked into this: Sabrina Carvalho, and Ian Kanski (who was also at NovelFarm 2019). The results looked promising. More on that in my next post.

Thanks to Sara for a very informative presentation. Hope to hear more about PCG in the future.

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