Traveller: Biospheres

When I was trying to work out how to feed Rethe, someone pointed me to High Guard’s biospheres, which I had completely overlooked.

Biospheres are amazing. Here’s what Mongoose’s High Guard has to say about them (page 59): This is an area dedicated to flora and fauna, either for the production of food or as a leisure area. Every ton dedicated to a biosphere eliminates life support costs for two passengers. Biospheres consume one Power and cost MCr0.2 per ton.

So 7m3 of biosphere provides 2200 kcals per day (800,000 kcals per year). And all it needs is some electricity (half a power unit per person) and some upfront capital.

Certainly, in terms of feeding a planet, a biosphere is a great idea. They’re small and efficient (if the text is accurate). But are they realistic for Rethe? And at what tech level?

Yield

A "biosphere" ?

Well, this is the greenhouse in our garden. By coincidence, and including the apex, it’s a little under 7m3. While we grow seedlings and some tomatoes, I would guess it probably provides about 2200 kcals per year, rather than every day!

My example hydroponic farms produced an annual yield of 1000 kcals per 0.325m2 per year. Assuming these farms are in racks 20cm deep (one of many big assumptions), that translates into 1000 kcals coming from a volume of 0.065m3. So 7m3 produces an annual yield of just over 100,000 kcals. So biospheres would need to be eight times larger.

What about mushrooms? Well, there are about 20 kcals in 100g of mushrooms, so you’d need 11kg of mushrooms for your daily 2200 kcals. I can’t see our greenhouse producing that. 

Or algae? If 100g of dried algae contains 300 kcals, you’d need about 800g of dried algae every day. Let’s assume algae has a water ratio of 85% (similar to seaweed), which means our biosphere has to produce over 5kg of algae every day. I can’t find any figures on algae production, but I doubt that sort of production rate is possible at TL 8 from a 7m3 volume.

A rich and varied diet

Current nutritional advice is to minimise ultra-processed food and eat a rich and varied diet – aiming for no fewer than 30 different plants a week. (For example, see here.) So a diet of algae is unlikely to be healthy. Now, at higher tech levels (say TL 12+, I can easily handwave all that and assume that science has solved that problem (although I suspect most people will prefer to eat fresh food). But at lower tech levels, we don’t have that luxury.

I have, however, ignored nutrition in my calculations and reduced everything to kcals.

Leisure areas?

I’ve also ignored the bit where High Guard describes biospheres as leisure areas. I’m finding it hard enough to imagine them producing enough food to cover life support, let alone thinking of them as a leisure area. (“I’m bored – let’s visit the algae vats,” said nobody, ever.)

High Guard optimistically describes biospheres as being dedicated to flora and fauna. I’m not sure what fauna anyone is expecting – animals are inefficient producers of kcals. Worms and bugs, maybe, but a petting zoo? Probably not – unless producing food is not your concern.

Other inputs

If you have a greenhouse, you’ll know that it requires many other inputs: compost, soil, seeds, water, sunshine – and time. (And a whole raft of tools and pots and other paraphernalia.)

While there are no running costs involved in a biosphere (other than power), I imagine a biosphere needing regular replenishment of nutrients and flora, especially at lower tech levels.

Tech levels

Speaking of tech levels, High Guard mentions nothing about biosphere tech levels. Given they are self-contained and require no additional nutrients or seeds or attention, I assume they’re pretty miraculous by today’s standards. So TL 10 at least. Maybe more. (So they’re not really suitable for TL 8 Rethe – maintaining them would be expensive.)

Or maybe, as I suggest above, they are simply larger at lower tech levels. Maybe something like this:

• TL8: 4 dtons per person (as a super-efficient hydroponic farm)
• TL10: 2 dtons per person 
• TL12+: 0.5 dtons per person (ie as per High Guard)

I imagine there would be other improvements in terms of other inputs and outputs as well. TL 12 biospheres probably produce synthetic meat and other textured vegetable protein – something the earlier models can only dream of. 

Summary

So, are biospheres any help in feeding Rethe/Regina, a TL8 desert world with barely any atmosphere and a population of 26 billion people? My estimate is no, not at TL8. As I said when I first looked at Rethe, I think it's TL should be much higher than 8.

Edit: Edited to add the summary.