3 ms·

what about contamination? urine is not always sterile upon elimination from the body, potentially bringing along bacterial, drug, and other contaminants.

Panino 5y ago
The composting process destroys pathogens by several mechanisms. The first is heat: in the pile, thermophilic bacteria raise the temperature through their own biological heat, killing E. coli, Salmonella, etc. My current pile was 149F (65C) yesterday. In a compost pile, those temps will kill pathogens in less than an hour. As a general rule of thumb the following temps/times kill pathogens in compost piles: 140F/60C for 1 hour; 130F/54C for 1 day; 120F/49C for 1 week. To measure this, you get a compost thermometer from a garden store and keep it in the center of the pile at all times, year-round. (The thermometer also serves another function: it indicates the degree to which your pile is biologically active, providing hints about moisture, carbon, and nitrogen levels.) So heat is the first mechanism for killing pathogens. Another is competition: the pathogens are directly killed by other bacteria in the pile. Once my compost bin is fully built, I let it sit for at least 1 year. The only thing to be really concerned with is certain chemotherapy drugs. Some of them not only don't break down in a compost pile, but they can cause cancer in people who don't already have it. The composting process is pretty amazing. It's vastly more hygienic than sewage (lol).
- hedgehog 5y ago
  I would also worry a bit about accumulation of drugs like lithium and other contaminants like PFCs. My suspicion is long term closed loop use of toilet compost for food crops could result in unsafe levels of contamination, have you done any research that direction?
  - Panino 5y ago
    I don't know about lithium in compost, but in general, composting breaks down many pharmaceuticals (again, apart from certain chemo drugs). Composting does destroy some anti-cancer drugs like Salinomycin. PFCs may accumulate almost regardless, although I assume composting helps. After all, composting can break down gasoline, diesel, and TNT - though of course you shouldn't add them to a compost bin! Quoting The Humanure Handbook (4th edition) page 115: "About half the sewage sludge (biosolids) produced in the USA is applied to land, providing a significant opportunity for contaminants to enter soil systems and to bioaccumulate over time..." And page 117: "For example, brominated fire retardants were still found at almost eight thousand times higher concentrations than background concentrations in soil samples twenty years after the last application of biosolids. In another study, fifteen out of nineteen pharmaceutical drugs were still present in soil six months after being irrigated with contaminated wastewater." So PFC accumulation is already happening but not because of composting. It's happening because sewage sludge is being added to farm fields and new housing developments. This is part of why I cook with clay (in solar cooking) and stainless steel on the stovetop. That way my nutrient loop (eat, excrete, compost, grow more food) has the absolute minimum of PFCs and other contaminants. For more information, read chapter 10 of The Humanure Handbook (4th edition) by Joseph Jenkins.
    - hedgehog 5y ago
      Lithium I picked as it's a heavy metal that wouldn't break down per se, though maybe the form it would exist in post-compost would be plenty benign. The sewage sludge issue I'm unfortunately aware of and have been following due to this case: https://www.mainepublic.org/environment-and-outdoors/2022-02-07/complete-crisis-as-pfas-discovery-upends-life-and-livelihood-of-young-maine-farming-family https://www.mainepublic.org/environment-and-outdoors/2022-02... In my area the majority of contamination is from firefighting foams, and I think in the Bay area there's also a lot in groundwater from semiconductor manufacturing. My understanding is the known way to remove PFCs from soil involves baking at very high temperatures (like 500C) which is impractical at any scale.
      - scotty79 5y ago
        Lithium is not a heavy metal.
        hedgehog 5y ago
        Hah, fair, it's actually light. I don't know to what degree it would get taken up by plants or other food organisms (chickens etc), but if it were then that could be a concern as it's a common medication and the net concentration could climb without removal.
    - netizen-936824 5y ago
      These are all great points, however the issue with PFCs is that they are extremely nonreactive. Things like TNT, gasoline, and diesel are the exact opposite. Those compounds are reactive and quite easy to break apart. Even so, there must be some sort of either precaution or processing steps that can be taken to minimize PFC concentration, although I don't quite know what they might be.
- clairity 5y ago
  i can certainly believe that composting is amazing at dealing with all sorts of contaminants, but as @hedgehog sorta points to, i'd be worried that the sheer variety of contaminants you could get at a larger population level would present some significant unknown/unforeseeable risks. on a smaller scale, like a single family/household, i'd expect those risks would be more ascertainable and mitigatable.

Panino 5y ago

The composting process destroys pathogens by several mechanisms. The first is heat: in the pile, thermophilic bacteria raise the temperature through their own biological heat, killing E. coli, Salmonella, etc. My current pile was 149F (65C) yesterday. In a compost pile, those temps will kill pathogens in less than an hour. As a general rule of thumb the following temps/times kill pathogens in compost piles: 140F/60C for 1 hour; 130F/54C for 1 day; 120F/49C for 1 week. To measure this, you get a compost thermometer from a garden store and keep it in the center of the pile at all times, year-round. (The thermometer also serves another function: it indicates the degree to which your pile is biologically active, providing hints about moisture, carbon, and nitrogen levels.) So heat is the first mechanism for killing pathogens. Another is competition: the pathogens are directly killed by other bacteria in the pile. Once my compost bin is fully built, I let it sit for at least 1 year. The only thing to be really concerned with is certain chemotherapy drugs. Some of them not only don't break down in a compost pile, but they can cause cancer in people who don't already have it. The composting process is pretty amazing. It's vastly more hygienic than sewage (lol).

hedgehog 5y ago
I would also worry a bit about accumulation of drugs like lithium and other contaminants like PFCs. My suspicion is long term closed loop use of toilet compost for food crops could result in unsafe levels of contamination, have you done any research that direction?
- Panino 5y ago
  I don't know about lithium in compost, but in general, composting breaks down many pharmaceuticals (again, apart from certain chemo drugs). Composting does destroy some anti-cancer drugs like Salinomycin. PFCs may accumulate almost regardless, although I assume composting helps. After all, composting can break down gasoline, diesel, and TNT - though of course you shouldn't add them to a compost bin! Quoting The Humanure Handbook (4th edition) page 115: "About half the sewage sludge (biosolids) produced in the USA is applied to land, providing a significant opportunity for contaminants to enter soil systems and to bioaccumulate over time..." And page 117: "For example, brominated fire retardants were still found at almost eight thousand times higher concentrations than background concentrations in soil samples twenty years after the last application of biosolids. In another study, fifteen out of nineteen pharmaceutical drugs were still present in soil six months after being irrigated with contaminated wastewater." So PFC accumulation is already happening but not because of composting. It's happening because sewage sludge is being added to farm fields and new housing developments. This is part of why I cook with clay (in solar cooking) and stainless steel on the stovetop. That way my nutrient loop (eat, excrete, compost, grow more food) has the absolute minimum of PFCs and other contaminants. For more information, read chapter 10 of The Humanure Handbook (4th edition) by Joseph Jenkins.
  - hedgehog 5y ago
    Lithium I picked as it's a heavy metal that wouldn't break down per se, though maybe the form it would exist in post-compost would be plenty benign. The sewage sludge issue I'm unfortunately aware of and have been following due to this case: https://www.mainepublic.org/environment-and-outdoors/2022-02-07/complete-crisis-as-pfas-discovery-upends-life-and-livelihood-of-young-maine-farming-family https://www.mainepublic.org/environment-and-outdoors/2022-02... In my area the majority of contamination is from firefighting foams, and I think in the Bay area there's also a lot in groundwater from semiconductor manufacturing. My understanding is the known way to remove PFCs from soil involves baking at very high temperatures (like 500C) which is impractical at any scale.
    - scotty79 5y ago
      Lithium is not a heavy metal.
      - hedgehog 5y ago
        Hah, fair, it's actually light. I don't know to what degree it would get taken up by plants or other food organisms (chickens etc), but if it were then that could be a concern as it's a common medication and the net concentration could climb without removal.
  - netizen-936824 5y ago
    These are all great points, however the issue with PFCs is that they are extremely nonreactive. Things like TNT, gasoline, and diesel are the exact opposite. Those compounds are reactive and quite easy to break apart. Even so, there must be some sort of either precaution or processing steps that can be taken to minimize PFC concentration, although I don't quite know what they might be.
clairity 5y ago
i can certainly believe that composting is amazing at dealing with all sorts of contaminants, but as @hedgehog sorta points to, i'd be worried that the sheer variety of contaminants you could get at a larger population level would present some significant unknown/unforeseeable risks. on a smaller scale, like a single family/household, i'd expect those risks would be more ascertainable and mitigatable.