Bacteria and Biofilters Are Underrated


Could it be that the logical conclusion of controlled-environment agriculture is natural ecosystems?

If controlled-environment agriculture is to become sustainable, it must be able to use waste as an input for nutrients. In 2016, the AVFami project group* realised that the best way to do this was through mimicking ecosystems. Toyoki Kozai also mentions this at the beginning of his book, which is otherwise about plant factories. In this way, waste can become an input, and internal waste streams can be inputs for other processes.

Aquaponics is not a closed system – obviously. There are inputs such as fish feed, and outputs such as fish and vegetables. There are unwanted outputs as well. One of these is solid waste. In most aquaponics systems, this gets filtered out and removed, to avoid the system going anoxic. Needless to say, this is a waste of nutrients (and energy too, even if it is only a bit). What can be done with this solid waste?

It might be possible to feed this to shrimp, something I know Seppe Salari is enthusiastic about. That’s a good idea, but for many farmers, why bother? Just another complex organism to get worried about, and I suspect the yield isn’t going to be that high anyway. Recovering that energy isn’t worth it.

In all ecosystems, plants are the primary producers. They are the only organisms capable of adding new chemical energy to the system, rather than concentrating it or recovering it; as shrimp, mushrooms, or insects do. To do this, plants need nutrients: waste where there is virtually no energy left, or completely mineralised. This is the endpoint obtained through downcycling. And it looks like even for downcycling, biology is the best way to go.

How so?

Last week, I was at NovelFarm 2019. One of the most remarkable companies there was INTAG (short for ‘integrated agriculture’). They use biological solutions to improve aquaponics, amongst other things. I moderated a panel including INTAG’s president, Ian Kanski, who made some great contributions to the discussion. His presentation was equally fascinating.

The panel discussion on indoor ecosystems at NovelFarm 2019. Left to right: Ian, Radu Giurgiu (PlantGeek), Mark Horler (UKUAT), myself, Vasileios Vallas (PlantHive), and Richard Blakey (Würth Elektronik).

INTAG are using an approach different to the upcycling ideas behind AMI (aquaponics, mushrooms, insects), and different to chemical/physical-based solutions. They have built an aerobic bioreactor (patented**) that mineralises the nutrients in solid waste so they can be taken up by plants. Deliberate downcycling, but still using biology. How does it work?

Aquaponics is often presented as the combination of fish and plants. This is true, but one group of organisms – arguably the most important – is often left out: the bacteria in the biofilter, which turn ammonia into nitrate. INTAG’s aerobic bioreactor is a supercharged version of that. In fact, the water in INTAG’s bioreactor is so oxygenated, that worms can live in it too. These bacteria and worms do things that give this bioreactor some unique features:

  • The bacteria chelate the nutrients, making them easier to take up for plants.
  • The bacteria act as a buffer for the system. Ian highlighted that the goal should not be to make a system sterile. That is impossible anyway. The goal should be to get the system as contaminated as possible, but with the right forms of life. Life will always invade, so it’s best we choose what gets there first.
  • And of course, the complete mineralisation of solid waste.

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Throughout his presentation, Ian highlighted some impressive claims about their systems: higher yield, far more flowering in banana and cocoa plants, and better predictability. They also managed to decrease the E.coli content of chicken manure by 99.9%.

The most impressive one, though was this: an aquaponics system that has been running for 3 years, with no discharge***!

That could be a gamechanger.

I’m not saying these systems are perfect yet. On fish waste, iron does need to be supplemented, for example. But this is a big improvement. Ian Kanski and INTAG aren’t the only ones who mentioned that adding more life to these systems was the way forward. Ulrich Knaus, from the University of Rostock in Germany, mentioned the concept of ‘polyponics’: using multiple species of fish and plants in aquaponics, for a more consistent nutrient profile in the system. This raises a lot of questions: is it worth it? How should such a system be managed? Should it be coupled or decoupled?

Anyhow, INTAG is another sign that the magic of biology should be embraced, and that biofilters are a useful way to do this.

* Now informally AMI’s Farm Lab. The original white paper is here.
** That said, I believe they have an arrangement where smaller companies are allowed to use it, as long as they send their data to INTAG.
*** I hate to put asterisks behind such an amazing claim, but for those wondering about sodium-based emissions: he said they just used high-quality input water. Fair enough, but it does beg the question of what to do in systems with high-sodium input water. Algae, perhaps?

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