Maintaining the correct moisture level is fundamental for successful decomposition. The process relies on aerobic microbes, which need both food sources and oxygen to efficiently break down organic material and generate the heat necessary for composting. If the moisture content rises too high, the excess water fills the small air pockets within the pile, effectively starving these beneficial microbes of the oxygen they require. This shift from an air-rich environment to a water-saturated one is the primary cause of decomposition slowing down or failing altogether. The optimal moisture range for a working compost pile is generally between 45% and 60% by weight.
Recognizing Over-Saturated Compost
A compost pile that has become oversaturated will display several distinct symptoms. The most direct diagnostic is the “squeeze test,” a simple tactile method for assessing the moisture level deep within the pile. To perform this, take a handful of material from the center and squeeze it firmly. If one or two drops of water emerge, the moisture level is at the upper limit of the ideal range. If a stream of water runs out or if the material has a slimy texture, the moisture content exceeds 65% and is too wet.
When the water content surpasses 65%, the compost transitions into anaerobic conditions, meaning it lacks sufficient air. This change forces a different set of microorganisms to take over, resulting in a distinct and unpleasant odor. The foul, putrid smell often described as rotten eggs or ammonia is a result of these anaerobic bacteria producing gases. Another clear sign of saturation is the cessation of heating, as the highly efficient aerobic microbes can no longer thrive.
Active Techniques for Immediate Drying
When a compost pile is identified as too wet, immediate action is necessary to reintroduce air and absorb the excess liquid. The most effective first step is aggressively turning the entire pile with a pitchfork or shovel. This action rapidly introduces fresh oxygen into the material, which helps the aerobic microbes recover, while simultaneously increasing the surface area of the damp materials for faster evaporation. Turning also helps break up any matted sections that are holding pockets of water, distributing the moisture more evenly.
Directly following the turning process, large amounts of dry, carbon-rich material must be incorporated to act as a sponge. These “browns” absorb the free water and restore the necessary air pockets within the pile structure. Excellent choices for this purpose include:
- Shredded newspaper or cardboard
- Dry leaves
- Peat moss
- Sawdust
- Shredded straw
Materials like peat moss are highly absorbent, and shredded straw also functions as a bulking agent, creating more space for air circulation.
A third technique is to spread the saturated compost out thinly on a tarp or concrete surface. Exposure to direct sunlight and open air for several hours accelerates the evaporation of surface moisture. Once the material feels noticeably drier, it should be thoroughly mixed with a substantial quantity of dry brown material before being returned to the main composting structure.
Long-Term Strategies for Moisture Control
Preventative measures and strategic structural choices are the most effective ways to manage moisture and avoid future saturation problems. The location of the compost structure is a major factor; it should be situated away from low-lying areas where water pools after rain or runoff, and not directly beneath gutter downspouts or roof edges. Protecting the pile from heavy or prolonged rainfall is accomplished by using a cover, such as a tarp or a purpose-built lid. This cover should be semi-water resistant but still allow some air exchange.
Maintaining the correct ratio of carbon-rich (brown) materials to nitrogen-rich (green) materials in the mix is a fundamental strategy for moisture balance. Green materials, such as fresh grass clippings and kitchen scraps, often have a very high water content. By ensuring a sufficient initial volume of dry browns, such as leaves, wood chips, or shredded paper, the pile has the capacity to naturally absorb the moisture released by the greens during decomposition. The ideal goal is to have a mix where the browns visually outweigh the greens by a factor of at least two to one.
Building the pile with proper base and structure further aids in drainage and aeration. Starting the pile with a base layer of coarse, bulky materials like small branches or thick straw creates a natural air channel underneath. This foundation prevents the material from becoming compressed and waterlogged at the bottom, allowing any excess liquid to drain away freely. Ensuring the compost bin or container itself has adequate drainage holes is also important to prevent water pooling at the base.