Humanure compost is safe to handle as treated material only when the hardiest organism in it, the roundworm (Ascaris) egg, has been killed, and the working standard is 55°C or more for at least 3 consecutive days at the coolest part of the pile. Bacteria die within about an hour at that temperature, so a pile that has only killed bacteria is not safe; if the temperature was not recorded, treat the compost as contaminated and use it only on non-food plants.
Part of Composting Toilet Systems
Pathogen kill requirements are the time-and-temperature conditions that make composted human waste safe. They are keyed to the most resistant organism, the egg of the roundworm, because anything that destroys it destroys the more fragile bacteria and viruses too.
The Most Resistant Organism Sets The Standard
Different organisms die at very different speeds at the same temperature. The parent page lists these kill conditions, all at 55°C:
| Organism | Time needed at 55°C |
|---|---|
| E. coli | 1 hour |
| Salmonella | 1 hour |
| Cholera bacteria | Minutes |
| Hepatitis A virus | Minutes |
| Ascaris (roundworm) eggs | Several days |
Composting Toilet gives the same organism as the benchmark and states 3 days minimum at 55°C. Where “several days” and “3 days” differ, 3 consecutive days is the floor, not a target to shave. The eggs have a thick shell, and the first-month page notes they survive weeks at 45°C and months at ambient temperature. So 40-55°C, the mesophilic band, composts the pile but leaves the eggs alive. A table that stops at the bacteria would leave a reader believing a pile is safe after one hour.
Time And Temperature Trade Off, But Not Freely
Kill is a combination. Hotter shortens the time needed, cooler lengthens it. The table above gives one temperature only, so do not infer a shorter time at 60°C or a “close enough” time at 50°C from it. If the pile never reaches 55°C, no figure on this page applies to it.
The Three-Day Figure Has An Uncertain Source
The parent page attributes “55°C for at least 3 consecutive days” to the World Health Organization. I could not confirm that attribution. The same figure, 55°C or more for 3 days in an enclosed vessel or aerated static pile, appears in United States EPA rules for composting sewage sludge (40 CFR Part 503), and that rule requires 15 days at 55°C or more with at least 5 turnings for an open windrow. I am recalling that regulation, not quoting it. The practical lesson stands either way: the larger and less uniform the pile, the more days and the more mixing the regulation asks for, and an unturned household bin looks more like the demanding case than the easy one.
What Each Kind Of Evidence Proves
| Evidence | What it shows |
|---|---|
| Smell, colour, texture | Aerobic microbes have finished; nothing about eggs |
| Core at 55°C or more for 3 days | The centre was treated; the shell may not have been |
| Coolest probe point at 55°C or more for 3 days | The treated condition, as far as you measured |
| Laboratory egg count | The only direct proof; not available without a microscope and training |
“It smells like soil” and “the bacteria are gone” are therefore not evidence of safety, because the eggs outlast both.
Time Is A Margin, Not A Substitute
The parent page asks for one full year of composting for humanure so the cooler edges are covered by extended time. The first-month page is stricter: if thermophilic temperatures were not confirmed it asks for 24 months minimum and still calls the result only “generally” safe. Those two disagree. This wiki has no sourced figure showing that time alone, without recorded heat, removes every viable egg; the sanitation literature reports eggs persisting in cool moist soil for a long time, as I recall, though not a figure I can cite. So:
- Heat recorded at the coolest point plus one year: garden use under Safe Application in Gardens.
- Heat not recorded: treat as contaminated. Use only on non-food plants: ornamentals, hedges and timber.
Worked Example: Reading A Temperature Log
Illustrative readings from a pile with probes at the core and at the coolest point (30 cm in from a corner):
| Day | Core | Cool point |
|---|---|---|
| 1 | 48°C | 30°C |
| 2 | 58°C | 36°C |
| 3 | 61°C | 41°C |
| 4 | 60°C | 47°C |
The core reaches 55°C or more on days 2, 3 and 4: 3 consecutive days. The cool point never reaches 55°C. Verdict: centre treated, shell not. The batch has not met the standard everywhere, so it goes to the year-and-restricted-use path, not the garden.
Common Mistakes
- Taking bacteria as the finish line. The hour-long kill times are not the safety standard.
- Probing only the core. The core is the best-case reading.
- Assuming a year makes any pile safe. It is a margin on a pile that was hot, not a replacement for heat.
- Mixing fresh waste into finished compost or using the same tool and wheelbarrow for both.
Safety
Viable roundworm eggs in compost can infect anyone who handles it or eats produce grown in it
Eggs are invisible and survive drying and cold. Wear gloves, wash hands with soap or ash and water, keep treated and untreated material and tools apart, and do not apply any compost to crops eaten raw or grown in the soil unless the heat record and the age are both documented.
What’s Next
- Learn next: Monitoring Temperature & Progress — probe placement and logging
- Combine with: Safe Application in Gardens — what the result allows you to grow