Anyone dipping their toes into the composting world may be wondering whether you can compost rotten food, or whether this could cause problems in the compost bin or your garden.
You may be worried that spreading mold spores and bacteria through the compost heap could contaminate or damage the soil, and spread the infection to healthy plants around your garden when you come to use the compost.
Fortunately, it’s usually not a problem to put rotten food in your compost heap, and many people do this. I have often added neglected cucumbers, leftover carrots, and mysterious bowls of forgotten veggies from the back of the fridge to my compost heap, with no adverse effects whatsoever.
However, there are certain situations in which you may want to avoid composting food that is turning moldy. Although the risks are usually fairly low, you can minimize them further by not adding potentially dangerous foods to your compost heap.
I’ll run over what you may want to avoid adding – but bear in mind that on the whole, rotting food won’t do any harm to your compost, your food crops, or you. However, it is important to keep any dogs away from compost that contains food waste, as it can be very harmful to them in rare cases.
Is Rotten Food Good For Your Compost Heap?
You might be wondering if mold can actually be beneficial to the compost heap. The good news is that it can – after all, the composting process is essentially just decomposing the food, and mold is part of that decomposition.
You may see mold in the compost bin from time to time, even if you don’t add moldy food to the heap yourself. The food you add is likely to form mold as it breaks down, and that’s nothing to worry about.
It’s sometimes a good idea to break up large areas of mold using a garden fork. You can spread it around and distribute it through the heap, and the worms will be better able to complete with the mold in breaking down the food waste. Large amounts of mold are unsightly and could occasionally pose a health risk.
What If I’m Allergic To Mold?
If you’re allergic to mold, you may want to treat this subject with more caution. If possible, let somebody else in the household handle moldy food and avoid letting it grow into large patches so that it is easier to deal with.
Even if you are not allergic to mold, it’s best to handle it with care, because it can exacerbate respiratory problems. No matter how healthy you are, you probably don’t want to inhale lungfuls of mold spores.
If you need to deal with large amounts of moldy food, you might want to put on a mask or put a cloth over your mouth and nose. This may feel excessive, but mold spores spread fast, and it’s very easy to inhale them.
Always clean down counters, crockery, and utensils that have been in contact with moldy food.
Food That Is Fine To Add To A Compost Heap
So, what can you safely add to your compost once it is past its best?
Most fruits and vegetables are safe to compost, even if they are more mold than food by that point. They are simply further along in the decomposition process, and they will break down nice and quickly in your compost heap.
Many molds will die once they hit the compost bin, because you’ll have changed the conditions noticeably enough that they cannot survive. Mold that has thrived in your fridge won’t like the new environment and will usually just disappear.
Even if the mold continues to thrive, it will disappear when the food has been used up and broken down into compost. Your soil will rarely end up moldy, and even if it does, it should balance itself out over a period of time. Don’t worry too much if you spot mold in the compost bin; it will soon go away.
So, briefly, you can compost pretty much anything organic from your fridge. Tomatoes, asparagus, bananas, carrots, peppers, cucumber, asparagus, and most other fruits and vegetables are fine to throw in the compost heap.
Fruits and vegetables should all compost well once they are in the bin, regardless of the mold they may have on them. Soft ones are popular with worms and will usually disappear more quickly, but even hard foods like potatoes will not hang around for long in the compost bin.
Cooked veggies that have gone moldy are okay too. However, you may want to be a little more careful adding cooked food scraps to your compost pile, as these can attract rodents and other vermin, which may not be ideal.
Cooked foods should disappear quickly in the compost heap, as they will usually have less structure than raw foods.
If you’re worried about attracting pests, try burying cooked food at the center of the compost heap and covering it with leaves, straw, or other unappealing foods.
Moldy citrus should not be added to your compost bin in large quantities. That is more because citrus can overwhelm the worms, rather than the mold itself. Small amounts of citrus should be fine, but adding large quantities isn’t great for your compost heap.
It seems unlikely that the mold on citrus will introduce anything harmful to the heap, so as long as the heap is big enough to cope with the citrus, you should be able to safely add it.
It might surprise you that moldy lettuce isn’t ideal for putting in your compost bin. After all, it will break down very quickly and disappear. However, there is a small chance that your salad greens could carry certain bacteria that might survive the composting process.
Salads can have listeria, salmonella, and E. coli in the leaves, and you don’t want to be incubating these in your compost pile, especially not if you plan to use the compost for food crops. It may be better to add green leaves to a non-edibles compost heap, or try hot composting to make sure bacteria is killed.
That said, I have personally composted moldy lettuce and browning salad myself for years without an issue. I have also never encountered any illness from green salads, so perhaps I have just been lucky.
Make a calculated decision about whether to add this sort of waste to your compost bin; the risk is probably low, but you need to decide for yourself whether it is worth taking for the sake of composting your greenery.
You shouldn’t add cooked meats – or even raw meats – to your compost, whether or not they have gone moldy. It’s best not to include these foods because they can attract pests, and there is also a low chance of them transferring bacteria to your compost heap.
If you are going to add moldy meats, you should only do so if you have a hot compost heap, as this should take care of any bacteria that might be spread by the meat.
I don’t add meat to my compost heap as I’m in a vegetarian household, but if you have a large heap that gets to high temperatures, you should be able to compost small quantities of rotten meat. It is best to cut it into little pieces and stir it throughout the heap so it can decompose.
What If I Notice A Lot Of Mold In My Compost Bin?
If your compost seems to be getting overwhelmed with mold, you might want to take action. Fortunately, this is usually fairly easy to deal with. Remember, molds need moisture to survive.
Lots of mold in the bin may indicate that it is getting too wet, or you’re adding too much wet food. Tear up some cardboard or newspaper, and stir this into the bin, breaking up the mold as you go.
Dry, absorbent food scraps such as bread are also helpful in tackling excessive moisture levels in the bin, as these will soak up moisture. They should also break down faster if they are wet.
How To Add Moldy Food To The Compost Bin
Many people recommend breaking up moldy food by chopping it or using a blender. I rarely bother, though I do break down big chunks of food.
The recommended method is to remove the top layer of compost, and add the moldy compost underneath. Cover with leaves or other dry material to help absorb moisture from the mold as this will kill it more quickly.
Covering the mold should help to prevent the spores from spreading around the garden if the wind picks up. Remember to wear a mask if you are sensitive to mold, and always wash your hands well after dealing with moldy food.
Composting moldy food is as easy as composting normal food – it’s going to go moldy in the heap anyway, if the worms don’t get to it first!
There aren’t really any dangers associated with doing so, and the only effect it should have is to break the food down faster.
If you find forgotten fruits and vegetables at the back of the refrigerator, toss them on the compost pile and recycle them into something useful!