Charcoal made from human waste could help solve fertiliser shortages as well as reduce pollution and energy use, a study has found.
Biochar is a form of charcoal made from organic matter treated at high heat, which is often used on farming soil as a fertiliser. The process also removes carbon from the atmosphere, making it a useful carbon sink.
The study estimated that biochar made from solid human excrement could provide up to 7% of the phosphorus used around the world each year. Although the biochar process converts only solids, nutrients taken from urine could be added to it, and the researchers found this could provide for 15% of annual phosphorus application, 17% of nitrogen, and up to 25% of potassium.
OK. Seems fair enough to me.
Treated sewage sludge is already spread on farmland, but its use is controversial as it often contains microplastics, heavy metals, Pfas forever chemicals, pathogens, and pharmaceuticals.The researchers say biochar can avoid this problem by separating the waste at source.
Ah, handwavey bit. If you can separate out the heavy metals at source then why do you need to use biochar instead of sewage sludge?
And the ‘carbon footprint’ of that process is? …
Carbon footprint? Oh, it’s all done with that excess power on windy, sunny days. And the carbon footprint of building all those windmills and solar was… is…
Here’s what confuses me. Renewable are supposed to produce loads of cheap electricity and the industry is supposed to create oodles of highly-paid green jobs. But jobs are a cost. How can the power ever be cheap if it requires loads of highly-paid people to produce it?
And carbon rather than sludge? Less smelly?
“then why do you need to use biochar instead of sewage sludge?”
In questions that can be answered: in biochar most of the carbohydrates that are in sludge are carbonised.
This not only concentrates and frees up the minerals you want per unit of mass, but the carbon itself is inert in soil, and can act as a soil improvement if used the right way, much like vermiculite or other porous granules work.
There’s also the bit where the sludge may have been sterilised, but it’s basically still shit. Anything that makes that nasty can and will grow happily in it if exposed to “The Environment”.
Same with fertilising with any other form of excrement, too much of a Good Thing™ will harm the soil, because the anaerobics you *don’t* want in overabundance will happily take over and well… mess up your field something fierce.
Turning the sludge into char avoids that, because you severely reduce the carbon content that can be metabolised by those anaerobics.
The firm I used to work for built (with an EU grant) a pyrolysis pilot plant to make bio- char. The local council refused permission for us to run the plant at our works without building a chimney stack x metres higher than the highest building on the site. This killed the project as the nearby fabrication workshop was about 30m high & the cost of the stack was more than the cost of the plant. We were located in the Black Country about a mile from the M5/ M6 motorways, an area not famed for natural beauty. The plant was designed to fit inside shipping containers for ease of re-siting, but nobody was interested. As soon as ‘pyrolysis’ was mentioned they lost interest. I should add that the plant came complete with an advanced scrubbing system to clean any off gas, but that made no difference against the dreaded P word. We were not too upset- we got all the money for building the plant & none of the agony of commissioning it…
The conversion of sludge to a dry solid also requires lots of water to be boiled off. Takes a lot of energy to boil water.
@Grikath: you still haven’t explained how the biochar process removes heavy metals and microplastics, which is what Tim was indicating with his ‘handwaving’ comment.
I won’t have sewage sludge on my farm, precisely because of the heavy metals/microplastics issue. You are basically paying to take someone else’s waste away, and contaminating your own land in the process. Sewage companies should be paying the landowner handsomely to dispose of the waste product, which might at least compensate for the potential contamination losses to capital values, but too many farmers are so short sighted all they can see is ‘Cheap fertiliser!’ and sign up not only to take it but also pay for the privilege. Idiots the lot of them. Farmers are their own worst enemies.
“And the ‘carbon footprint’ of that process is? …”
I think the same thing when I pass a local timber supplier advertising “Kiln Dried Firewood Logs”…
Jim:
I think the microplastics will be made not so micro, and not so plastic either with the heat involved.
But heat does nothing to remove the heavy metals. So there’s that.
Any article with a headline ending in ‘a study has found’ can be skipped.
“But heat does nothing to remove the heavy metals. So there’s that.”
I suppose if they make the process hot enough, the heavy metals will evaporate up the chimney and just cease to exist?
“Forever chemicals”: what, like water?
@Jim, As mentioned above, any “microplastics” would cease to be plastic to begin with. Same goes for PFAS, most, if not all, of the pharmaceuticals, and any and all pathogens.
You turn the sludge into charcoal through pyrolysis, after all… Pretty much nothing based on carbon chenmistry will survive that…
As for the Heavy Metals…
Unless the primary stream is polluted in some way by some external source of heavy metals, the heavy metal content of the sludge would be exactly the same as its biological origin.
It’s there, but it’s basically trace presence, in amounts actually neccessary for healthy organisms.
You’d drop dead pretty sharply if all the lead, antimony, arsenic, chrome and strontium, to name a few, were to be removed from your body.
You concentrate the amounts in the process, to detectable levels even, but you won’t be spreading a tonne per acre…. You’d be using it as fertiliser, which means the heavy metals present would actually enrich the soil for trace elements.
Especially the heavy metal bit is funny, since plants actually use more of them per weight, and people have no problem whatshowever of using All Natural Compost, even when the actual level of heavy metals in that stuff is way higher than in typical char.
So yeah… all of it is basically a non-issue.
“The researchers say that biochar can avoid this problem by separating the waste at source”
So do they each use three toilets, one for heavy metals, one for microplastics and one for agricultural fertiliser? And how do they manage to separate the constituents of their excrement before visiting the toilet?
“As for the Heavy Metals…
Unless the primary stream is polluted in some way by some external source of heavy metals, the heavy metal content of the sludge would be exactly the same as its biological origin.
It’s there, but it’s basically trace presence, in amounts actually neccessary for healthy organisms.”
Er no. Sewage sludge is specifically tested for heavy metals because it gets contaminated by a) what people put down their drains, both legally and illegally, and b) what gets washed into the the drains from roads and hard surfaces etc. All of which gets concentrated in the sewage treatment process. So you have to be very careful with applying sewage ‘cake’ to land, if you over do it you can end up with land that is so contaminated that it breaches statutory guidelines for food production. Thats why the sewage companies will test your soil before agreeing to let you have the stuff, to make sure you are nowhere near the limits. If you are, no sewage sludge for you.
And it matters not if the contamination of the sewage is pretty low, because it tends to get put on the same fields (being only able to be spread where arable crops will be grown, so it can be cultivated into the soil) so over time a constant incorporation of lightly contaminated material will result in a fully contaminated field. This isn’t a ‘apply once only’ operation, its an ‘apply repeatedly year after year’ one.
‘solid human excrement’
Gamecock is envious.
Thanks, Grikath at 11:29. This post had me believing Brits poop heavy metal.
Doesn’t Parliament separate turds from the human race?
Following the logic of the biochar industry, the waste from a forest fire must be superb for soil enhancement and future carbon sequestration. Just not the fire itself.
>the waste from a forest fire must be superb for soil enhancement and future carbon sequestration. Just not the fire itself.
Genuine question: if that weren’t the case, wouldn’t the forests in California, Canada, Australia and so on have died out millions of years ago, instead of coming back good-as-new after a wildfire passes through?
Even better than that, BM, St. David of Attenborough has pointed out in several documentaries how some species need to burn in order to propagate and reproduce. Gum trees in Oz, several species in S. Africa come to mind.
Wildfires are a natural phenomenon, not a climate disaster. The majority are started by lightning strikes, which as I understand it are still not anthropogenic. (Many of the rest are started by arson, which certainly is.) It’s not surprising that some species have evolved to take advantage of fire and its consequences: bare, fertile ground; no competition.
“Wildfires are a natural phenomenon, not a climate disaster.”
Death is a natural phenomenon. No, seriously, it is Man who hates death; nature doesn’t care.
Pinus palustris, the longleaf pine, a southeastern US coastal species, is conspicuously adapted to fire.
@CharlesBrecknell
“located in the Black Country about a mile from the M5/ M6 motorways, an area not famed for natural beauty” – that would be near or in the Sandwell Valley, which is a lovely rural area that is fairly beautiful, shame about the M5 and M6 that run through it – we did things differently in the 60s and 70s.
I would ask how biochar, treated at high heat – shit burnt in an oxygen free environment – is removing CO2 from the atmosphere?
Back in the early 70’s Slough sewage works manufactured “Cinagro” fertilizer.
All I can find online is that there is an archived undigitized copy of a report “Disposal of sewage sludge: use of Cinagro fertiliser by Slough Council”. It is archived under the heading of chemicals in food.
I vaguely recall sales being stopped due to Cadmium levels. There was however another side effect that I remember well. Wherever you used it tomatoes would often sprout from the seeds that had passed through human digestive systems and the sludge drying beds.