A compost aerator is a tool which is used to increase air circulation in a compost pile, promoting rapid breakdown of the substances in the pile. Several companies manufacture tools specifically designed for compost aeration, although a shovel, pipe, or stout stick can do the job as well. For home composters, a compost aerator or rotating compost bin which aerates when it is spun is a critical tool for rapid, successful, and low-odor composting.
In a home compost pile, bacteria and fungi work together to break down organic material, generating a nutrient-rich black material which can be used for gardening. Temperatures in a home compost pile rarely climb that high, so the compost pile tends to house bacteria which require airflow to survive. As compost breaks down, it compacts, and the compaction slows down the bacteria, and the subsequent rate of decomposition. One of the most immediate problems with poorly-aerated compost is a strong stench.
A compost aerator breaks up the compost, introducing fresh air to the depths of the pile so that the bacteria inside can thrive. Compost aerators are very easy to use; all the gardener needs to do is jab the aerator into the compost bin several times to stir up the compost. As an alternative, people can compost in a bin which spins, allowing the user to twirl the bin to aerate the compost. People sometimes refer to this as “activating the compost,” stressing the idea that the flow of fresh air gets the bacteria and fungi inside the compost active again.
Without periodic aeration, a compost pile will start to become unhealthy. Discarded items will take a long time to break down, and the compost may develop a strong and unpleasant smell. If a compost pile starts to work much more slowly than it has in the past, it is time for an aeration session, unless it is winter, in which case the bacteria may have slowed down on their own. Introducing compost amendments like straw can also speed the composting process, as can adding worms for vermicomposting.
It is possible to compost anaerobically, but this requires much more work, and a huge supply of compost. Industrial and municipal composting facilities often use anaerobic techniques, with the temperature of the piles rapidly rising to high temperatures which promote a profusion of thermophilic bacteria, breaking the compost down very rapidly. Most home gardeners lack the facilities for anaerobic composting, making a compost aerator a necessary tool.