Compost contains living microorganisms and bacteria that need air, moisture and something to feed on. If you are just throwing waste into the compost pile, that is known as cold composting and it can take up to 2 years for compost to be ready.
However, if you using a compost tumbler it is known as hot composting and it will be ready in about 6 months. For hot composting you need to use high-nitrogen materials and increase the air exchange by turning the pile. Whether you buy bagged compost or make your own, it is best to use it right away.
However, as anyone who bought bags of compost or made your own, you might be wondering what will happen if you left the compost too long?
If you leave compost in the pile, in a bag or bin too long, it can still be good to use for years as long as you control moisture levels, cover it and store it in a dry place. But gradually it will break down, nutrients will leach and compost can start to rot as well as it can get contaminated with fungus.
Does compost go bad?
Although compost doesn’t go bad, it gradually breaks down and is worked in the soil by earthworms. If the compost in the pile or tumbler just finished, you can store it for the growing season next year. So, on average, a ready compost will last for a year keeping in mind that you need to add it to raised garden bed or border soil in spring.
How long compost lasts on the soil depends on the climate. In a dry and cool climate it will last longer rather than in a hot and humid regions. It will gradually loose nutrients because of lots of rain and snow. If you bought compost bags, these usually don’t have a shelf life and you won’t find an expiry date.
As with the home made compost, you need to use compost from the bag straight away. But can a bag of compost go bad? Here is a thing – as long as the bag is sealed and the moisture level is low, the bacteria in a compost bag will continue to decompose indefinitely!
It can go bad if somehow bag got opened or moistened. Then it will go into anaerobic digestion and you can recognize it by a putrid smell emitting from it. So, as long as it has a pleasant, earthy odor, compost is good to go. Don’t worry, the nutrients won’t be lost inside the bag.
How long can you keep compost?
If the compost in compost pile or compost tumbler just finished and it is well rotted, you need to use it on garden beds or ground as soon as possible. If you have some finished compost left after amending garden soil, you can keep it for six months.
Keeping compost for longer, especially during winter or in cold climates can lead to rot and loss of valuable nutrients. If the moisture levels are off, compost can get too wet and mold can develop. On the other hand, it can dry out completely and will be not useful at all.
Can I use old compost?
Generally, you have to replace compost or at least third of the compost every year. That is because nutrients in compost will be exhausted after a growing season. It’s not OK to use compost that is older than six months because it can get contaminated with fungus, start to rot and loose all the nutrients.
Moreover, you can’t reuse compost or just add fresh layer on top of the existing one because it gets compacted. When growing medium is compacted, roots are not able to breath because there is not enough air in the compost. Heavy watering will also increase compaction. Compaction is one of the most common reasons why soil gets muddy.
If you left compost too long and it became old, just use it as mulch. Spread it around the roots or use on top of plants in the garden. Although it doesn’t provide nutrients, this compost will prevent weeds from growing and will lock in moisture.
If you are new to composting and don’t want to wait for years until it is ready, then hot composting in compost tumbler is the great option for you. You don’t need to worry about turning compost, just keep the green and brow ratio right as it is the most common reason why compost tumbler is not heating up.
What composting method are you using? Hot or Cold? If you want to share your composting hacks, feel free to leave a comment down below!
Happy composting!
