I hope this isn't too broad.

I'm talking about large scale industrial composting. So you take a city's sewage, treat it (irradiating is one method I've seen mentioned) and modify it as needed. Then apply it to crop lands. Even applying it to non-edible locations (parks, etc.) would seem to be better than current "circular" treatment.

From the little that I know so far, putting treated sewage sludge on crops is effective and economical. It was tried here in Virginia (according to a crop scientist I spoke to from Virginia Tech) but there was resistance (probably racial) to putting "urban sewage on our crops". (Most sewage comes from concentrated areas. Most applications are in rural farmland.)

  • What does irradiation do to 'clean' the sewage? The problem I've just learned this past decade is that they don't spray this on crops like silage, they inject it into the earth 20 - 15 feet below the roots. The root zone is only 6" at most. It goes into our subterranean 'river' systems. Yes, traveling through bedrock and soils will 'filter' some of it but we are talking ALL of human poo goes into our aquifers except the little bit that gets processed into mulch. They take big tankers out to the agricultural lands where they can do this more on the 'down low'?
    – stormy
    Commented Jul 7, 2018 at 21:19
  • I've seen the test results of this stuff. Wonderful beautiful mulch. Again, I wouldn't use anything BUT this mulch on landscapes but I would never use this on vegetable crops. Food crops. In fact, they are supposed to acknowledge this shouldn't ever be used on Food Crops. That link said it was fine to use on vegetable gardens. It is not. The heavy metals falling from our skies from geoengineering are adding to our soils and water...changing the pH of soil even in our wilderness areas. People growing food in Hawaii are using greenhouses to minimize the heavy metals in their soil.
    – stormy
    Commented Jul 7, 2018 at 21:25

4 Answers 4


As far I know, it is already done. Sewage is often "cleaned" and the solid was often used as fertilizer. I think on industrial size, on recent time, it was done as research project in Germany.

The problem is that humans are no more so natural being. We eat a lot of (non-organic) chemicals (and medicines and hormones) which go to our solid waste, which could enter again into food, which is also no so much healthy (taken without control).

For this reason now it is difficult to do in industrial case on our cities. (but so there were such research project, to see if we could remove metals and nasty stuffs).

Note: technically it is not a compost, like for manure (of cows, of horses, of chicken, etc.). it is just better not to use it fresh.

  • Human poo mixed with sawdust and completely decomposed is compost. Decomposed organic mulch/compost. The only negative thing about human poo plus sawdust decomposed organic matter is heavy metals. No other stuff. They find higher levels of heavy metals in tap water and even the soils of our forests. No organic matter should ever be used 'fresh'. I lived in Japan where they had all the homes have their poo and pee drained into Honey Buckets. From there, very fresh indeed, it was bucketed on the shoulders of the rice farmers to dump in the rice paddies. I think this is the norm today.
    – stormy
    Commented Jul 6, 2018 at 7:53
  • 2
    @stormy it's not so much that the heavy metals are in the faeces, as that they get flushed down the drain from other sources and mixed with the faeces
    – Chris H
    Commented Jul 6, 2018 at 12:05
  • If any of our drinking water happens to be part of what gets flushed down the drain Hydroflurosilicic acid plus arsenic, plus lead, plus mercury and that is not only in our drinking water (in the states) it is in our preserved, processed foods, all of our soft drinks, juices, Cheerios...not a shred of evidence for dental benefits nor any health benefits and lots of evidence for horrendous maladies hard to know the culprit. This 'industrial waste' would cost so much to dispose of as decreed by law that...well, Great party conversation let me tell you.
    – stormy
    Commented Jul 7, 2018 at 3:32
  • @ChrisH Who knows what people flush down the toilet? The bulk is feces. We humans consume so many chemicals especially heavy metals. And then we actually have the audacity to dump industrial waste on purpose...on purpose into our drinking water in all major cities. Pediatricians give tiny babies with no teeth fluoride tablets. Only good thing there is that the tablets are pharmaceutical grade, not the buckets of 'unknown' dumped in our cities' water.
    – stormy
    Commented Jul 7, 2018 at 3:37
  • @stormy: no evidence of dental benefits? Really there are so many evidences (now diminishing, because we are more rich and educated, so we care more about teeth). BTW Fluorine is one of the most frequent element in soil, so no problem with plants. Heavy metals, antibacterials and other medicines are worse (the first because they are absorb and concentrated by some plants, the other because they cause resistance and damages of growing soil. Commented Jul 7, 2018 at 5:26

I am so impressed, Clay! This is one of my biggest soap boxes. The only problems with our poo is that we are omnivores and we take lots of drugs.

Do you have human poo mixed with sawdust and thoroughly decomposed available? You are one lucky person to have this resource. In the states it is federally supervised and tested 5X...before it is available to the public. After decomposition (I think this is done anaerobically), the ingredients are not at all the same chemically. Smells wonderful. Looks beautiful, a dark taupe color. Fine fine textured. No rocks. No clumps. No sticks. No chunks. No pesticide residues and no weed seeds.

This was the only mulch I would use to mulch plant beds. I refused to use bark, chips...non decomposed organic matter. I never lost a single customer.

You should ask for a readout of a test of the mulch. You will KNOW what is in every batch. What this stuff does for a landscape is phenomenal. I am not kidding. Adds a tiny bit of nitrogen but it feeds the soil, the soil organisms work symbiotically with plants. Inside ONE WEEK, after installing this for mulch on the soil of the plant beds the plants look amazing. My guys, my crews were blown away at the difference. Gorgeous.

There is ONE bad thing about mulch made from human poo and that is heavy metals. Humans take medications that are made with heavy metals and that is distilled and pooped out by humans. I've never used this mulch in my vegetable gardens. BUT! Knowing the amount of heavy metals in our tap water and now our soils is making me WANT to use this mulch on my beds in my greenhouse.

I refused to use any other mulch on my landscapes; new or maintained. My bosses flipped but I stood my ground and never lost a single customer. The landscapes I maintained sold my basic basic techniques and my bosses backed off. Let me make the decisions and sell.

And make happy solid customers.

In the commercial world that won't fly. Very very sad. I asked (Sawdust Supply, Seattle, WA) the owner, great guy, what happened to the poop that wasn't decomposed and made into mulch (Gro-Co) and I was told happily that it was trucked to the center of Washington State and pumped 15-20 feet below the commercial crops. I heard that he thought that benefited the crops somehow?

Gulp. If you think about it, root zone is 6" max. Pumping our poo into the ground 15 to 20 feet deep means it is going into our fresh water systems. Our government is dumping our poo into our water tables...our fresh water systems. Without testing, monitoring or public knowledge.

Clay, please ask pointed questions of your municipality.

  • Yep, your previous answer inspired more more specific question (first dog poop, then human!) Commented Jul 6, 2018 at 5:23
  • Hey, I am very much an organic girl! Whatever that means!! I also know what works and what does not. Always open for new stuff that makes sense, however!
    – stormy
    Commented Jul 6, 2018 at 8:00
  • They would probably have to do this on mars. We could also make poo burgers by harvesting the bacteria out of the poop. Yummy protein poo burgers. Mmmm...
    – user22106
    Commented Jul 6, 2018 at 15:55
  • @user22106 Did you see 'The Martian'? Matt Damon? There are two things very wrong with the science the rest is very honest. The first was the wind/dust storm on Mars (not much wind on Mars, little puffs might make a big looking dust storm)? The second problem was using non decomposed Matt Damon poop to grow potatoes in 4" of soil??? (hey, I read the book, always better). when you eat rice from Asia you are eating rice grown in human feces and pee pee. From community Honey Buckets...
    – stormy
    Commented Jul 7, 2018 at 3:46
  • We can already make poo burgers though but i think i just read an article about the community poo and pee buckets used in rice patties, unless it was on here. I want to see that movie though. @stormy . They harvest the bacteria and then kill it of course with something to make it edible. Not raw poo. I think though to answer the question the main obstacle is that people dislike the idea of eating poo even if we make it safe. Lol
    – user22106
    Commented Jul 7, 2018 at 4:27

This is actually done on a commercial scale in Bristol, UK where I live. Sewage (and food waste) goes to an anaerobic digester that makes biomethane as a fuel, but the solids left afterwards are (to quote the image I linked):

Biosolids are one of the end products... and are an excellent soil conditioner...

250,000 tonnes [per year] goes to benefit local agriculture...displaces the need for inorganic fertiliser.

But despite producing renewable energy and fertiliser, the project isn't doing too well financially. It's not immediately clear to me whether this is because it's expensive to pioneer a new technology, or whether it's actually not financially viable.

  • I think, Chris, that this very responsible way to put our poo poo to good use is just too responsible, mitigates our urban areas turning into deserts by the use of wood chips. This information (1994??) did not know about the heavy metals as we do now. Such an emphasis on heavy metals in this mulch (and it is a bit substantial) yet not a word about the levels in our tap water. Way higher. Heavy metals are accumulative in animal bodies. Some plants such as moss and kale are 'indicator' plants. They accumulate best? Governments are not the least bit interested in our health.
    – stormy
    Commented Jul 7, 2018 at 3:57
  • Decomposed organic matter is always super for a 'soil conditioner' and weed suppression. It is not fertilizer, yes there might be a bit left over but should never be used as THE fertilizer in a fertilizer program. It is not being used for commercial agriculture in place of balanced 'inorganic' fertilizers. It is being pumped below the crops out of sight and into our fresh water systems.
    – stormy
    Commented Jul 7, 2018 at 22:01
  • 1
    @stormy true enough. Even the people who make it only say it's a good source of phosphorus (though it should have some nitrogen as well) and not that it's a generally fertiliser.
    – Chris H
    Commented Jul 7, 2018 at 22:19
  • Sawdust Supply has been making this mulch for at least 3 decades. I had no idea it was not being done at all sewage facilities. Just a few? There is no phosphorus or potassium that I know about, just nitrogen and heavy metals. Anaerobic decomposition must not use as much nitrogen as aerobic. Gotta go check this out. I do know putting that stuff on a landscape was the closest thing to magic I know...one week and the landscape plants were vibrant, green, healthy...major wow.
    – stormy
    Commented Jul 7, 2018 at 22:31

There are two main types of composting, fungal, and bacterial. As the name suggests fungal composting uses fungi, and bacterial composting uses bacteria.

The fungal strain Stropharia Rugoso-Annulata (godzilla mushroom, king stropharia, wine cap) has been known to kill ecoli, which would help you do what you're trying to do. Paul Stamets has been doing this for years with sewage, and proved in Puget Sound that it can treat runoff water for the salmon run.

for how he treats sewage see: https://www.youtube.com/watch?v=SSKQyMFw8GM

If you want to do this with water in a pond you could try this experiment:
inoculate large logs with king stropharia
push them into a pond so they can float and fruit while on the water
eat the mushrooms as desired

Joel Salitin, et al uses chickens to sanitize his pastures which would work well also for your solution, as if they won't eat it they will scratch it up looking for the insects eating it furthering the breakdown speed of the fecal matter.

  • I thought the two types were aerobic and anaerobic composting. Bacteria and fungi are at work in both. Chickens sanitizing pastures? Putting stuff in ponds that doesn't normally grow in ponds? He is using these rotting logs to clean sewage 'ponds'? I'll go watch this video...
    – stormy
    Commented Jul 6, 2018 at 7:59
  • There's both present, but the difference is how they're dominated. Think outside the box a little based upon what they need then put it in an unnatural environment and since logs that have lost some mass due to mycelium have removed some weight from the logs they should float logically. I like to think between the circles to make things work together. Commented Jul 7, 2018 at 4:13

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