Friends, Not Food: The Role of Plants in Space
And fish, and birds, and resurrected woolly mammoths
Note: all illustrations in this piece were produced using DALL·E 2
A lot of people are trying to grow plants in regolith. Some of these studies are iffy in that they’re using orange-colored “analog” regolith sourced from outdoors, essentially demonstrating that plants grow in dirt. But others are pulling out all the stops and using the real stuff.
All this is predicated on the idea that when we expand to space, we’ll take with us the Neolithic-aged paradigm of growing our food in the ground. Apparently, this is too obvious to be questioned because almost everyone is going along with it unquestioningly. I see this played out quite often: we’ve done X on Earth for thousands of years, so of course we’ll keep doing X in space. I don’t think people making these assumptions are necessarily conscious of it, they just can’t or won’t expand their thinking beyond the current thing.
But plants simply aren’t efficient. Typical crop plants convert sunlight to biomass with only 1–2% efficiency. They also take a long time to grow: 55 days for soy, 80 days for corn, 120 days for wheat. And they’ve been co-evolving with soil for many millions of years in an intricate symbiosis that will be hard to reproduce in all its complexity. If it were straightforward, we would have factories churning out replicas of the black soils of Iowa to spread around parts of the world that could use it. True, we can use hydroponics to some extent, but notice vertical farms sprouting up in urban centers are limited nearly exclusively to lettuce and microgreens: not exactly dense in calories.
In “Feeding One Million People on Mars” published back in 2020, I was on the right track in ditching protein-from-slaughter in space for cellular meat from bioreactors and imagined a hypothetical diet which also included plants (consider this the mea culpa) and insect products.
Then a few things happened. In March 2021, Ashley Beckwith and colleagues demonstrated cellular agriculture with plant cells rather than animal cells. In other words, if you can grow a steak in a reactor then you can grow an apple too. Later that year, Cai et al. ditched cells entirely and synthesized starch from carbon dioxide with a total efficiency of something like 7%, way above even the more efficient C3/C4 plants. This advance is a big deal and has caught peoples’ attention (87 citations in less than a year so far).
So if I were to re-write the Mars paper today, I’d probably go with a breakdown more like this:
(1) Cellular meat (including insects & seafood)
(2) Cellular plants
(3) Starches and other simple molecules produced through electrochemistry
Three categories of building blocks, all done in (bio)reactors, then endless combinations to build up palatable textures and flavor profiles. What about single cell proteins? Maybe a small role, but I’m not as bullish as Nord and Bryson even though they have the right ideas about ditching crop plants, and they cover much of the above in terms of plant efficiency. The issue with SCPs has always been palatability: I’d challenge anyone who thinks SCPs are the answer to eat more than a tablespoon of Spirulina in a sitting.
I don’t think plants are useless in space. I’m fully behind Elliot Herschberg’s interpretation of Viriditas, and terraforming in general. If nothing else, we need to do something with the biochar left behind after gasifying solid waste, and it makes for a pretty good fertilizer. Let’s just ditch the part where we eat the stuff that comes out of the ground: a spacefaring civilization can do better.