Farming in Space and Multicropping: an Unlikely Connection

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The systems approach is a powerful one. Different ideas from different disciplines can be plugged into a coherent structure, to test new combinations and look at how they can work. Professor Eldert van Henten highlighted this with examples of engineering solutions from aerospace being applied to agriculture.

The systems approach is universal, and a lot can be learned from stepping outside of one’s field. To improve conditions on Earth, we can look to the skies. Nevertheless, today’s article will be about something more explicitly linked to agriculture, albeit still in space.

The colonisation of Mars is a controversial project. People like Elon Musk say that it is the only way to save the human race from extinction. Others see it as a misprioritisation – a lofty goal not worth pursuing until conditions on Earth are satisfying for everyone.

This is a false dichotomy. Exploring space doesn’t bring development on Earth to a halt. On the contrary. By pursuing goals in space, we learn more about how to improve life on Earth.

A major challenge in colonising Mars is keeping the crew fed. This applies everywhere in space. On the ISS, the costs of delivering food from Earth range from $10 000 to $20 000 per kilo. And most of that ‘food’ is just packaging. There’s a huge need for developing life-support systems. In other words, we need to learn how to grow food in space.

This is one of the many reasons that the European Space Agency (ESA) started The Micro-Ecological Life Support System Alternative (MELiSSA) in 1989. MELiSSA aims to mimic ecosystems to feed the crew in a closed loop, which the crew is of course a part of. It’s a massive project involving 30 organisations across Europe, including one near me in Belgium.

Part of MELiSSA involves growing plants hydroponically. This was the topic of Professor Danny Geelen’s talk at the AVF’s Brussels Workshop.

Currently, the systems used are quite similar to an LED-lit grow container, albeit a hyper-insulated one. That said, these systems still have a 5-10% leakage. 93% of the water is recycled, but that’s still 7% which is lost in the process. There is a lot to be improved.

To grow plants in space, extremely sterile conditions are required. Hydroponics is seen as sterile, but it’s only in space where we start to see that it is nowhere near sterile. During a plant’s life, the roots constantly shed cells. Everything is food for some form of life, and dead root cells are no exception. There are microbes who are happy to make use of this, and so their numbers grow over time. But these microbes do much more. Their interaction with the roots changes how nutrients are taken up, influencing the plants’ health.

The kinds of microbes that populate hydroponic water depend on the kind of plant being grown, since this determines the type of cells that are shed. The microbial composition even depends on the plant’s age. If microbes play a role in nutrient uptake, then it is important to optimise their composition. As a consequence, multicropping could have a role in spacecraft hydroponics. That means it could be used to improve yields on Earth too.

I don’t know where these microbes come from in the first place, and how the people from MELiSSA are planning to use this knowledge. It would certainly be interesting to know, though.

The broader lesson is this. By looking at perhaps the most sterile way of growing plants, we have found a use for multicropping, something associated with permaculture, considered the opposite of sterile. Farming confronts us with biology, no matter where it’s done, and different settings teach us different things. Suddenly, a seemingly irrelevant idea like multicropping can show its relevance in a setting where it is unheard of.