WPenner's Blog

Enter the Worm

"How long could a worm live in space?" I pondered this odd question last week after coming across a bit of space gardening research from Iowa State University. Fans of The Martian know just how compelling space gardening can be!

A group of researchers looked at the ways to overcome the harsh environmental conditions on Mars, namely the salinity of the water available, the lack of soil, and the basalt character of the rock. Their recently published experiment used bacteria to desalinate water and then plant turnip, radish and lettuce in a basaltic regolith simulant. The results showed planting alfalfa and using it as a biomass dramatically improved the plant success. Radishes, for example, were three times more successful with the biomass. ¹

Using alfalfa to improve soil quality is common here on earth, where farmers often grow and then plow it back into the ground because of its ability to add biomass (i.e. carbon) and nitrogen into the soil. The finding made me wonder about other organic approaches to improving soil quality. Specifically, I wonder about vermicompost.

Why Worms?

In the summer of 2019, I received 1 tablespoon (~5) Red Wriggler (Eisenia fetida) worms from a public composting demonstration. Over the intervening years I've grown that initial tablespoon into a population of several thousands and produced several dozen kilograms of vermicompost from kitchen scraps. Somewhere along the way, I became something of a worm fan, then a worm geek, and now my first thought to any problem is, "maybe worms can solve this". It's a long stretch from kitchen scraps to Mars agriculture, though, so what are the possibilities?

For those who haven't drunk the worm Kool-aid yet, here are some important facts to consider:

• Vermicompost, is the best soil amendments available, with a nitrogen to carbon ratio that plants thrive on.
• "Vermicompost" is a polite, technical way of saying "worm poop". A less scientific sounding, but equally polite, term is "worm castings".
• Compost worms will eat most organic material including vegetable scraps and manure.
• Composting with worms is many times faster than other forms of composting.
• Under ideal conditions, composting worms can eat their weight in scraps every two days and double in population every 2-3 months.
• As food passes through compost worms, it gets coated in mucus, which provides an ideal substrate for many other beneficial micro-organisms.
• Depending on the feedstock, the bioavailability of critical nutrients like potassium and calcium improve significantly. Because worms have a gizzard (like birds) instead of teeth, ground egg shells commonly provide grist to help them digest food. The ground shells provide calcium and balance ph levels. Another common form of grist is rock dust, which provides different nutrients.
• Worms' ability to remediate heavy metals is excellent, providing additional safety to the colony.

All the above facts suggests the possibility of taking alfalfa (and other plant waste items) and feeding them to compost worms and using the resulting vermicompost to further improve plant results. Other waste, like animal or human manure, could provide further feedstock, improving the overall sustainability of the human colony.

With vermicompost's ability to remediate and amend soil, over several growing seasons, the soil would improve. Improve the soil and crop yields improve. Better crop yields provide more feedstock for the worms and a virtuous cycle results. Small pieces of basalt chipping off would integrate into the soil after being ground down in the worm's crop. So, the vermicompost cycle makes sense, at least on paper. Which leads back to the initial question of whether worms would survive in space.

Worms in Space?

Surprisingly, worms have been in space before. From the late 90s to mid-2000s, a microscopic worm called C. elegans was used to study radiation exposure to biological systems. After spending 8-10 days on the ISS, the worms were sacrificed to look for DNA and other changes related to the high radiation exposure of space. ² This research suggests that other worms might provide different useful services in space.

One (cheap) way to test the viability of the worms in space hypothesis is sending a batch of worms and compostable material in a stratospheric balloon to the top atmosphere. Such balloons, capable of staying aloft for up to 45 days, provide a long enough window to determine aspects of worm efficacy such as production level of vermicompost and procreation.

A fairly simple worm habitat providing oxygen, food, bedding (such as shredded newspaper or cardboard) and heat to maintain a constant temperature around 30ºC is all that is required. Multiple compartments could provide a base sample and experimentation with different feedstocks. A more complex set-up with a camera and other recording equipment would provide ongoing tracking of the experiment.

In designing such an experiment, two factors could negatively impact the results: warmth and vibration. Warmth plays a significant factor. My personal observation is that worms have the best appetite around 27ºC with sharp drop-offs the further the temperature gets above or below that. Worms are also sensitive to vibration and being suspended may provide enough shocks to the habitat to make them very nervous. Worms protecting themselves just aren't in the mood to eat.

Further Consideration

While I don't have a definitive answer to the viability of worms in space today, the possibility of improving gardening in harsh environments like the moon or on Mars is worth exploring.