Composting in a plastic bin offers a space-saving, contained method for recycling organic waste into a valuable soil amendment. While this approach keeps the material neatly contained, it introduces unique challenges compared to open-air piles, particularly concerning oxygen supply. Aeration, the process of introducing oxygen, is necessary for successful decomposition by aerobic microorganisms. Managing the confined space of a plastic bin requires specific techniques for turning the material to ensure these microbes thrive.
Why Plastic Bins Require Specialized Aeration
The enclosed, vertical structure of a plastic bin fundamentally changes how air moves through the compost. Unlike open piles that benefit from passive airflow, the bin’s walls restrict lateral air movement. This lack of circulation means that oxygen consumed by microbes in the center and lower layers is not easily replaced, creating an anaerobic environment.
Material inside a bin also experiences significant vertical pressure, leading to rapid compaction over time. This compaction reduces the air pockets, or “free air space,” between the organic particles. When the material becomes dense, aerobic decomposition slows, and anaerobic bacteria take over, resulting in foul-smelling compounds like hydrogen sulfide and putrescine. Because a standard pitchfork cannot effectively mix the dense material within the bin’s narrow opening, specialized methods are required to break up these compacted, oxygen-starved zones.
Step-by-Step Turning Techniques
For stationary plastic bins, the most direct method involves internal stirring using specialized compost aerator tools. These tools are typically long shafts with folding wings or a corkscrew-like spiral, designed to be plunged deep into the bin. As the tool is pulled upward, it catches the material, lifting and mixing the lower layers with the upper, oxygen-rich material. This action creates vertical air channels and brings cooler, less decomposed material from the edges into the hot core.
A DIY solution involves using a length of rebar or a sturdy pipe to poke numerous air holes throughout the pile. While this technique does not fully mix the material, it fractures compacted zones and allows oxygen to diffuse into the center of the bin. For smaller, more durable bins, physical tumbling or rolling is effective. The bin lid can be sealed, and the entire container rolled forcefully on its side across the ground, mechanically tumbling the contents for a thorough mix.
If the compost is severely compacted or too heavy for internal stirring, a full layered removal may be necessary. This involves placing a tarp next to the bin and emptying the entire contents onto it, layer by layer. The material is then returned to the bin, reversing the order. This ensures the fully decomposed bottom layer ends up on top, while the fresh or partially decomposed top layer is moved to the bottom. This complete turning ensures every part of the pile is exposed to oxygen and mixed for uniform decomposition.
Establishing a Consistent Turning Frequency
The frequency of turning depends on the microbial activity within the bin, which can be monitored through simple sensory cues. The most reliable indicator that turning is needed is a drop in the internal temperature of the pile. When actively composting, the material should reach temperatures between 130°F and 160°F; a sustained drop below 130°F signals that the microbes are running out of oxygen and need to be refreshed.
Another clear sign for immediate turning is a strong, unpleasant odor, often described as rotten eggs or ammonia. These odors are direct byproducts of anaerobic decomposition and indicate that oxygen levels have become too low. For a fast, hot composting process, turning the material every three to seven days is common practice to maintain high temperatures and oxygen concentration.
For a slower, less active system, turning may only be necessary once a month, provided there are no foul odors. Regularly assessing the bin’s moisture is also part of the turning schedule. If the material feels dry, turning while adding a small amount of water helps distribute the moisture. Conversely, if the material is overly wet, turning helps introduce air and can be corrected by adding dry, carbon-rich material like shredded cardboard or dry leaves.