If you are composting food waste and garden waste, you are probably wondering how you ensure that nothing dangerous survives the composting process. This is particularly important if you compost meat or animal feces. With that in mind, let’s look at a compost temperature to kill pathogens ( Temp guide lines).
Compost needs to be maintained at 131 degrees F for at least 3 days in order to kill pathogens. You can use higher temperatures, but the compost should not dip below 131 degrees F. Lower temperatures will deal with weed seeds, but will not deal with pathogens. Hot composting is therefore necessary if you are concerned about pathogens.
In this article, we’ll explore how you kill pathogens in your compost using high temperatures, and how you can boost the temperature. We will also look at the drawbacks of hot composting.
What Temperature Will Kill Pathogens?
To get rid of pathogens in a compost heap, you need to raise the temperature in the heap above the highest temperature that pathogens can survive in. Temperatures as high as 120 degrees F will kill some pathogens, even if these temperatures are only reached for an hour or two, but to reliably kill all pathogens, you need a higher temperature for a longer period.
It is recommended that you maintain a temperature of 131 degrees F for at least 3 or 4 days to ensure you kill all pathogens. A lot of people don’t bother to do this, but if you add certain ingredients to your compost heap, it becomes extremely important.
For example, if you add animal waste from carnivorous animals (e.g. cat or dog waste), or if you add meat to the compost, there’s a much greater risk of dangerous pathogens breeding within the compost. If this is then used for growing food, these pathogens can pass into the food, and could make people sick when they eat it.
Some people choose to maintain the temperature even higher, and may keep their compost heaps at as high as 150 or 160 degrees F. If it’s maintained, this will certainly kill all pathogens, leaving your compost safe to use for food crops.
How Do You Make Compost Hot?
There are several things you can do to raise the temperature of your compost heap. One of the most important things is regularly turning the compost heap. This adds oxygen to the center of the heap, which helps the good bacteria. The bacteria produce heat as they break down the food, so the more active these bacteria are, the hotter the compost heap will get.
Having the right mix of greens and browns is also critical. Green ingredients are wet, including things like food waste, grass clippings, and any other greenery from your garden. Brown ingredients include things like cardboard, straw, eggshells, and other dry ingredients.
The ratio will vary depending on where you are in the world, and different sources will recommend different ratios, but a 50:50 mix often works well. If you have too many browns, the compost will be too dry and won’t break down well, but if you have too many greens, the compost will be too wet, and the bacteria will suffocate.
You should therefore check how wet or dry your mix is by squeezing a handful of it. You’re looking for the consistency of a damp sponge. No moisture should drip out, but it should feel damp. If the heap is too wet, try adding some torn-up cardboard, and if it’s too dry, get some grass clippings or something similar.
You can also cover up a compost heap to keep it warm inside. Some people use natural carpets, sheets of cardboard, etc. You can also buy a hot composter, and this will trap heat very effectively.
It’s also important to make sure your compost pile is large enough. Compost piles should be at least 3 feet in each direction, as this ensures they have enough mass to trap heat inside the heap. If your compost heap is smaller than this, it will not retain its heat, and keeping it above 131 degrees F may prove impossible.
What Are The Drawbacks Of Hot Composting?
Although hot composting is excellent for killing weed seeds and pathogens, there is a drawback too. The good bacteria will be killed by high temperatures as effectively as the bad bacteria, and this can result in your compost heap becoming inactive.
If the temperature goes above 160 degrees F, the good bacteria that help the waste to break down will quickly die. This stops the compost from being broken down, and it will quickly lose its heat. You will have to wait for the bacteria to re-form before it will break down further and regain its heat.
That means you need to balance your compost’s temperature with care. Use a thermometer to check it isn’t getting too hot. If you do find the temperature is rising too much, spread the pile out more so the heat can escape, and reduce how frequently you are turning it.
To reliably kill pathogens in a compost heap, you need to raise the temperature to or above 131 degrees F for a minimum of 3 days. You can raise the temperature higher than this and keep it hot for longer, but it’s best not to let it rise above 160 degrees F, or the good bacteria in the heap will be lost.
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