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BSFL on human waste

I was reading about different insect integrations with waste streams and came across this one:

objectives To determine the capacity of black soldier fly larvae (BSFL) (Hermetia illucens) to convert fresh human faeces into larval biomass under different feeding regimes, and to determine how effective BSFL are as a means of human faecal waste management.

methods Black soldier fly larvae were fed fresh human faeces. The frequency of feeding, number of larvae and feeding ratio were altered to determine their effects on larval growth, prepupal weight, waste reduction, bioconversion and feed conversion rate (FCR).

results The larvae that were fed a single lump amount of faeces developed into significantly larger larvae and prepupae than those fed incrementally every 2 days; however, the development into pre- pupae took longer. The highest waste reduction was found in the group containing the most larvae, with no difference between feeding regimes. At an estimated 90% pupation rate, the highest bioconversion (16–22%) and lowest, most efficient FCR (2.0–3.3) occurred in groups that contained 10 and 100 larvae, when fed both the lump amount and incremental regime.

conclusion The prepupal weight, bioconversion and FCR results surpass those from previous studies into BSFL management of swine, chicken manure and municipal organic waste. This suggests that the use of BSFL could provide a solution to the health problems associated with poor sanitation and inadequate human waste management in developing countries.

So, feeding Black Soldier Fly Larvae fresh human faeces resulted in FCR of 2.0–3.3, which is better than a lot of insects, and better than BSFL on a lot of manures.

Now, you wouldn't want to eat these, probably, but they could be sterilized (chemically, like fermentation, or with heat) and fed to animals. Chickens, in particular, would be a good one for this, maybe dogs, too.

An average human excretes 1.1 kg of faeces per day, which could make 330-500 grams of BSF daily! That's enough for several chickens.



  • The more I study this, the more I realize this is a revolutionary development that has gone unnoticed.

    Ok, so we know you can produce 330-500 grams of BFL per day per adult human (at 40% protein, that's 132 g of protein). That's more protein than the human requires, but people probably wouldn't want to eat grubs fed on their feces (though, maybe with sterilization and processing, like bug tofu).

    So, combine that with some grain and/or other food waste (using BSF as primary protein), and raise some chickens that lay eggs. 330g BSFL with 990g of other feed, that's 1.3 kg of chicken feed, or enough to feed 7-9 laying hens. With 7 laying hens, that's ~5 eggs a day, which would provide about 1/2 of the protein required by the adult human.

    Route that same feed through crickets or mealworms, and you'd come close to providing all of the protein an adult needed. Like chickens, you'd need to dilute the BSF with other stuff, but with both of these, you'd produce more insects biomass out than BSFL in.

    Imagine a world where the vast majority of human protein is produced on the waste of the human itself. That would revolutionize the agriculture world, and drastically reduce livestock production (though could leave room for poultry and pigs without added resources).

    Why aren't we doing this?

  • Ok, found some errors in data, human feces isn't 1.1 kg per day, it is closer to .4-.5 kg per day. So, that's ~166g-250g of BSFL per day per adult. So, enough to cover protein directly, but not enough routed through chickens. Still, very good.

    Also, reading on urine, there is enough nutrients in urine to grow 50-100% of the grains a human needs per year. And supposedly, with intensive methods, that could be done in 100 m2 of space.

  • Hi VelaCreations, - Urine from rural farmers on humble diets is about N:P:K of 11:1:2 & so for every liter human urine there's 11g. Nitrogen, 0.8gr. Phosphorus & 2 gr. Potassium. If an adult urinates a little under 1.5 L per day that's good ~500 liters per year then it's good for 5.6 Kg N , 0.4 Kg P & 1.0 Kg K. Urine from well fed people will have proportionally more nitrogen & different phosphorus/potassium ratios. Incidentally human feces has a higher % of P than found in our urine.

    Urea makes up most of that N (+/-59%), so applied directly to soil the urea needs to convert into ammonia, gas off some ammonia & wait for the soil nitrosomes to convet it into ions of nitrite (which can be toxic to plants). The soil needs to have nitrobacter convert the nitrite into ions of nitrate (nutritional for plants); if the soil's got enough of the right microbes this urea conversion into usable nitrate would take less than 2 weeks.

    Allow for the total urine nitrogen to have about 80% efficiency of utilization by plants as compared to commercial nitrogen fertilizers; it's not linear that for every gr. of urine N the plant will have it's full benefit. If urine can be allowed to stand around in containers for a couple of days it's easier to get into plants; it's due to hydrolysis where NH2CONH2 + H2O ->NH3- ions plus NH4+ ions plus 4CO3- ions.

    The potassium (K) content is proportionately low in urine. The rural solution is to put bannana peels or comfrey leaf in the standing urine during it's hydrolysis. Sediment that precipitates is then both magnesium ammonium phosphate & calcium phosphate; these are even compounds that can be even be stored for use if you've too much fluid urine volume to use.

    Probably the most significant fertilizer you could isolate from the urine is the phosphorus (P). When add MgCl2 it binds with the N & P to form struvite (ammonium magnesium phosphate); which is (NH4)MgPO4-6(H2O).

    If the ratio of Mg added is 1.3:1 P of urine content then 99.2% of the struvite recovered will be an ortho-phosphate; plant roots take up ortho-phosphate & the struvite crystals are used diluted. Figure it's will only incorporate less than 4% of the original N in urine; it will be about 5.35% N to 13.24% P & 0.30% K & 9.5% Mg & 0.18 % Ca & 0.09 Na & 0.05% S.

    Making struvite is not complicated; it's only how to maximize it's crystalization out of solution. Basically at high pH the ammonia can't react with the urine's phosphorus (P) so reaction should be done at least below 7.8pH & preferably below 7.5pH. If you want to get fancy then re-elevating the pH to over 8.0pH will cause the newly formed struvite to more readily precipitate.

    If experimenting bear in mind you don't want to shear the ionic bonds that are realigning. Once add your Mg reagent (can use evaporated seawater's Nigari if no MgCl2 available & near ocean sea-salt pans) stir the urine blend at a low RPM instead of a high RPM; at 100 RPM you'll get maximum phosphorus (P) recovery as struvite, stirring at 300 RPM will yield the poorest struvite forming & at 500 RPM you'll get the maximum amount of total minerals in the urine precipiting (but not ortho-phosphate struvite).Stir the brew for at least 15 minutes & up to 1.5 hours; any mixing done past 1.6 hours is not going to get any more struvite out of the process.

    As an aside you might want to know that cow urine is usable for agricultural synergy. Uses include: for bacterial leaf blight, fusarial wilt, helmihthosporium leaf spot & ripe rot.

    One can mix the following proportions 5 Kg cow dung : 1 Kg clarrified butter : 5 L cow urine : 3 L cow milk : 5 L water & stir daily for 15 days then filter out the solids. This can be used as a foliar spray diluted 1 part of brew in 10 parts water applied every month (or as per lore on the day of the full moon).

  • In the discussion of peeponics ( they talk about bottling urine for 2-3 weeks to convert to ammonia. Hydroponic delivery is probably the best method for max efficiency of utilization of plants.

    Struvite is mentioned in the last pages of that thread, where a person added a small bit of epsom salt (Mg) to the urine to produce Struvite. It dissolves in the hydro solution easily for delivery.

    That peeponic thing was very interesting. They were using about 200 ml of urine (approx 1 pee) per day or every other day to maintain at least 1.5 m2 of plants. Taking this to full utilization, that would be at least 15 m2 of intensive plant area per adult human, year round. I'm not certain, but I think a faily complete diet could be grown in that space.

    They also added some trace minerals and earthworms in the growing media to add trace minerals.

    Interesting about the cow urine, I wonder if other animals (rabbits) could be used?

    Combining an insect recovery of feces nutrients (BSF) with a urine/hydroponic system seems like the route to produce a full diet in the smallest space with the least external nutrients.

  • here's some info about nutrients in urine, as well:

  • Hi VelaCreations, - Having looked at your link just want to say that purely adding in magnesium in any form may form a precipitate of phosphates. However, struvite formation is a bit more precise of an operation.

    At time of blending with magnesium the extraction of human urine processed at > 10.5 pH yields no struvite, at > 9.5 pH struvite yield is > 30% less of maximum, & at 8 - 9 pH struvite yield is 30% less than maximum purity. At >8 pH the Calcium present forms up Ca3(PO4)2 & the Potassium forms up MgKPO4; the closer to 9 pH one's processing of human urine is performed then the more these 2 phosphates are the actual precipitate instead of struvite.

    Calcium bound phosphorus (P) holds that P unavailable at high growing media pH condtions. If the plants are actively growing & synthesizing organic acids that are sent down to the roots for exuding those acid protons ("+" ions) will make the P soluble.

    However, since organic acid exudation is not a steady state event the situation leads to swings in P uptake from Ca bound P. Bear in mind that the link you gave was for hydroponic use of calcium phosphate/magnesium phosphate urine derivative & for roots sitting in water there forms what is called a Nerst layer; this is a somewhat static film next to the roots in solution that hold acidic H+ ions & a Nerst layer does lower pH.

    What the plant needs those organic acids for, & thus won't just send all made to the roots, is the following. Ammonium (whether fed as fertilizer or bio-converted inside the plant from nitrate absorbed) is the only way plants make amino acids & synthesize proteins. The process itself of making amino acids uses an intermediary molecule (alpha-ketoglutaric acid) & this same intermediary is normally used in a series of energy producing reactions (called by some the Krebs cycle & others the tri-carboxylic acid cycle).

    So, the plant must substitute another organic acid into the energy producing cycle to pick up the slack from alpha-ketoglutaric acid being used when making proteins instead of participating in generating energy. In other words, the plant develops vital proteins (ex: enzymes, chlorophyll-protein complex) better when it's organic acids are available for duty rather than steadily shunted down to roots for dealing with calcium bound P.

    Organic acids are also relevant because the general interior of a plant cell is ~ 7pH (with some interior cell organelles ~5 pH); metabolism inside the cell spins off acidic compounds (ie: "+" charges). To keep their interior region's 7pH the cell has to degrade some it's organic acids to offset the acidification; or, alternatively, pump out some"+" ions like K+ (phosphorus) or H+ & then bring in a "-" charged ion (OH-), which expends energy during pumping.

    It is the swing upward in plant cells' interior (cytoplasm) pH that diverts carbon, which the leaves photosynthesized into themselves, from just being made into sugar/starch that let's the cell form that new carbon into amino acids, protein & lipids (membrane,oil). And so, when leaves are not making sugar that's when there's some organic acid outflow (instead of organic acid degradation) which get transported down to the roots for exuding to lower the pH to make those non-struvite phosphates soluble for uptake. (Note: if your growing soil is actually an alkaline soil please advise so can nuance that.)

    Meanwhile, if the phosphorus (P) gets low in the plant it's proteins start to degrade & then free amino acids are loose, due to the way low P induces the stoppage of protein synthesis. In robust growth, when there is a lot of plant tissue or actually still forming organs (ex: buds,leaves, shoots, inflorescence) , P levels can get low & growth only goes on for a short time; this is why old leaves send P to the growing shoots.

    On the other hand, if you overload phosphorus in the growing media then that too will reduce plant growth. In excess it will reduce the uptake of micro-nutrients & even calcium; or, depending on the pH, precipitate the micro-nutrients & their deficiency makes it hard to diagnose what symptoms might show up later. (Note: your link said they needed more iron (Fe) & that dilemma might have been due to a pH inter-relationship with their urine phosphates ionic composition; but that's another story.)

    Whereas actual struvite has ammonium, which creates a different set of circumstances because of it's (ammonium) dynamic with the roots leads to lowering the pH & thus the P availability. In young plants that are not yet producing a lot of organic acids & wants their organic acids for back-up intermediary molecules (or sacrifice to spurt up inside cell pH) during protein synthesis the struvite is going to provide more uptake of the urine's phosphorus (P) without relying on the organic acids it made.

    If one is not adjusting human urine's pH downward at the time of beginning with the stirring/processing then a theoretical calculation of the end products' phosphate can not be made as to what is any of the sediment's actual struvite form of phosphorus content. While, at as low as 7 pH it is possible to recover >95% pure struvite, but the rate of precipitation must be slow to achieve this level.

    Fresh urine's urea will undergo 100% hydrolysis in 30 days at a reasonable ambient temperature. If only 25% hydrolysis has occurred it is still possible to extract more than half of the potential struvite. By adding commercially obtained pure enzyme urease at a rate of 50 mg/L(-1) human urea in urine takes less than 2 hours to be ready. Therefore, add >10% aged urine to fresh urine as an inoculate having existing urease (in aged urine) & then your urine will be ready for high yield struvite processing after only 48 hours, if temperature kept >20*Celsius.

  • wow, thank gringojay! I think I may test a small peeponics system this summer, just to see what the potential is. I have seen and grown different hydro setups in the past, and the best performance always were from the ones that were a wicking-bed type setup, which means they had gravel with the hydro solution, and then a layer of compost/soil on top. The compost/soil wicks the moisture and nutrients up to the plants, and as they get larger, their roots make it down into the solution as well.

    This type of setup has several advantage, the main one being that deficiencies are far more rare, because of the nutrient balance in the compost. I find that the vegetables taste better as well.

    It's also a lot easier than a typical hydro setup, because you don't need to keep things sterile.

  • @VelaCreations, I like your way of thinking! The more I'm working with insect s, the more I realise entomophagy is probably just not going to be popular enough to compete in any way with traditional meat and fish or soy meal. We need to produce insect on waste (wether human faeces or any other biowaste) so we can lower our ecological footprint and then feed insects to poultry so we can still eat meat. This way we'll get the best Of both worlds. Eventually, I suppose, hoppers will become somewhat of a land-shrimp, which would be good, because hoppers actually are tasting good.

  • The way I do it here, I raise both the chickens and the insects on waste. And instead of eating the chickens, I eat their eggs (but we eat rabbits that consume waste grass and weeds).

    Routing their manure back into an insect conversion system is important, too. Right now, I am experimenting with mealworms on herbivore manure, and I have been feeding omnivore manure to BSF for several years.

    We compost all human waste, which is good, we are able to return it back to the loop, but routing it directly through insects and plants (in the case of urine) is far more efficient.

  • Manure as feed substrate for black soldier fly is mentioned in Forum threads & since site organization poor will post this study out of Wageningen University here. It has good specific data on manures even though not dealing with human manure & I think search function might bring this thread forward enough for future readers.

    Using dried & reconstituted non-human manures Oonincx, vanHuis & vanLoon (2015) completed the report "Nutrient utilization by black soldier flies fed with chicken, pig or cow manure", originally published in Journal of Insects as Food and Feed; free full text link =

    Table 1 shows the black soldier fly pre-pupae (at time of experiment protocol collection) will weigh the most when fed cow manure (7.4 +/- 1.4 gr. each); yet will require the longest time (214.5 +/- 21.6 days) to get to that point, with the 2nd best survival rate (87.8 +/- 5 %). Best comparative manure fed survival rate (97 +/- 4.7%) was for pig manure; yet they had the 2nd best fresh weight (6.9 +/-1.4 gr. each). On chicken manure they needed the absolute least development time (144 +/-33.1 days) to pre-pupae (which was statistically not much better than pig manure fed development time of 144 +/- 52.8 days); while weighing the least (5.68 +/- 1.6 gr.) & having the lowest survival rate (82.2 +/- 13.5%).

    Table 2 data , among other specifics, gives excellent break down of how much nitrogen, phosphorus, etc. is left in the different manures after being fed to black soldier fly larvae. Anyone trying to remediate different manures for an ecological purpose can get an idea of some non-linear results to consider; the text's "Discussion" has more clarification on this.

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