Recycling Human Waste (in space)


Hello all, there was some discussion about pee and poop in a recent episode so I thought a thread that breaks things down might be beneficial as its certainly NOT rocket science and actually can benefit our lives if handled properly err scientifically.

So for starters I think most of us already know that urine is recycled on the ISS.

However feces is not and that kind of struck me as a bit of a shame. Then again space is at a premium up there and the downside issues of handling human waste means that its simpler to just bag it up and dispose properly. That is the engineering solution.
However our waste has many uses, some of which are discussed here

Here in Japan where they don’t really have a shame culture around the human body or its waste, its known that in the past farmers used to charge rent to a room with 1 tenant. 2 tenants per room could stay rent free and 3 in a room actually got a small stipend from the farmer at the end of every period. Why you might ask ? The farmer was collecting the poo and putting it into the fields as fertilizer.

So there are many issues when dealing with human waste and how to treat it properly. The simple rule is to separate the physical from the liquid. Its why compost toilets have different holes for urine and feces. The poop is collected and allowed to dry out. Once it has had sufficient time to “dry out” it becomes very similar to garden quality fertilizer. There are a number of other difficulties regarding vectors for disease and the diet of the human poop we wish to re-purpose. In a dry place like California I’ve read that anywhere from 3 to 6 months is sufficient to turn poop into great garden stuff.

In space that probably isn’t an option, however it can be utilized in a number of ways as discussed in the article above. There are plenty of stories about it. Here is another one.

Vegetarian humans without disease can have their waste recycled without issue. Obviously thats just my opinion but the totality of human history pretty much confirms this statement to have merit although I suppose it could be challenged as an over-simplification. However its a message board and as such it functions as the town board and hopefully will garner some feedback.

/rant Since given our current meat production system isn’t a sustainable option for humanity over the long term, vegetarianism is clearly the better option. The meat production statement will not be backed up with data since anyone with google can find this to be true for the most part. Slaughtering animals for food is not only morally wrong but factory farming is toxic and the waste gases produced from the billions we kill annually is poisoning the air as well. /endrant

We are indeed what we eat. I would highly recommend anyone with interest in the subject check out Valter Longo or Peter Attia. Both are medical doctors.
Here is Doctor Longo’s diet Daily Longevity Diet - Valter Longo Foundation
In addition periodic fasting also improves the human condition. The scientific evidence is overwhelming here.

So I think we are looking at a number of issues that all point to the repurposing of feces in space as a primary tool for existing away from mother earth.

Although its slightly off topic from this subject, the total amount of plant material needed to close the human CO2/O2 cycle is known, although details such as trace elements and plants living in zero g have yet to be mastered. Clearly the future path to space involves humans valuing waste as life sustaining.

Its my first post here so I didn’t want to say anything too inflammatory, although I will admit that I couldn’t resist the temptation to flame meat eaters :kissing_heart: I myself eat some meat, although its mostly fish and occasionally chicken as both are farther down the food chain. I hope this inspires someone to post their feelings on the subject as I think this particular issue will go a LONG way towards humanity reaching our near term goals and buying enough time for newer tech that can bypass the chemical constraints that will enable us a species to become a multi solar system species.

Thanks for reading


Love your post and I agree that the way we eat meat is extremely harmful and unsustainable over the long term. But I’m not giving it up altogether and I think there will always be some meat-a-sauruses among us. Of course, even non-vegetarian poop can still be recycled. It just takes a bit more effort. So I say let’s focus on moderation and recycling in any way we can.

Not trying to change your personal beliefs. It takes guts to stand up for them. Just saying I come from a slightly different angle and still think that your basic plans are viable.


Not sure what to do for the waste in space… but on Mars it would be precious as it would be the only source of Nitrates… Mars may not have nitrogen in the atmosphere and soil(nitrates) which can be used to grow vegetation/algae/proteins. I am sure the Mars travelers will be keeping their wastes for fertilizer.


A little gravity makes pluming a lot easier… A spinning station or ship with a spinning section in which the bathrooms and processing equipment are housed would make processing the waste a whole lot easier as well as the process of depositing the waste a whole lot more pleasant.


Indeed and thanks Cogiflector. I appreciate your comments.

Did I mention that I eat fowl and fish ? :sweat_smile:

Regarding the eating of meat and the factory farm system that supports it, I’ll share a great comment I heard from one of the numerous CEO doing startups in the meat lab space. She said “We know that the price of factory farm meat is unlikely to go any lower, while lab grown meat is only going to get cheaper.”

IMHO if you know anyone interested in a career, that is a great place to start.

Meat from a jar.

mm mm, finger licking good :vampire:


The Biosphere 2 experiment, to me, is a red flag as to long-term nutritional needs of people in a sealed environment.

We could do hail-mary flag planting flights to Mars with a couple intrepid astronauts. To do this with dozens, if not hundreds of people before we do the former is extremely dangerous (see prior reference to Biosphere 2).


Mars has a 1.89% share of nitrogen in the atmosphere and nitrogen in to the soil too. And you can not just use waste to feed plants without treatment.

They just did the experiment wrong, as far as possible. In BIOS-3 experiment lasting 180 days for 3 people a cycle closure was achieved almost of 100% in water and air, and around 80% in food (meat was supplied from outside). The only drawback in this experiment is that the experimenters spent too much time caring for plants. But with modern automation level it is no longer a problem.


Actually, the problem with biosphere is that it was an attempt to recreate an entire ecosystem.

Food production can be a lot more floor space, crew time, and energy efficient if you don’t bother adding tonnes of different biomes (like ocean and desert) like the biosphere project did.

If you can find it, there’s a great papar about growing food at the south pole:
Patterson, L. G.A. Giacomelli, P.D. Sadler. Resource and Production Model for the South Pole Food Growth Chamber. doi:10.4271/2008-01-2011. SAE Technical Paper 2008-01-2011. 2008.

also there’s the eden project which is a successor of this:


Indeed, I am sure that there are far more efficient ways to not only save space, labor and energy but that certain biomes have a synergistic effect on the environment.

Thanks for the Eden link Faulx !

and of course to TMRO science for their recent episode on the polar “greenhouse”