In-Vessel Forced Aeration Composting Process

By Home & Garden Last updated Friday, May/24/2024

Composting Methods

According to the University of Florida IFAS Extension website, there are four main types of composting systems: static piles, forced-aeration static piles, in-vessel composting and turned windrows. The method chosen for any given compost pile is based on the amount of land, money and labor available; the amount and type of materials to be composted; the desired end product; and the amount of time needed to produce that product. For instance, not all composting facilities wish to produce the fully cured product of compost, which is humus. Some wish to decompose the material to a lesser degree for easier disposal. An in-vessel forced aeration system is a combination of an in-vessel system and a forced aeration method.

In-vessel systems are also known as compost bins and closed-reactor systems. Gardening supply stores often sell compost bins for home use; these are small in-vessel systems. Vessel methods place compostable materials, such as food and yard wastes, in partially or entirely enclosed containers. In non-forced aeration systems, bins are turned to provide oxygen to the decomposing material. In-vessel systems are more efficient for the space used in comparison to the other options, but they are also more expensive.

Forced aeration systems are used in large-scale composting facilities to provide oxygen to decomposing materials. When used in combination with in-vessel systems, perforated flooring or pipes are installed in the bottom of the bins, which is connected to a pump that either draws or pumps air through the pile. This keeps the pile oxygenated.

The materials in a healthy compost pile are digested by aerobic microorganisms, or microorganisms that require oxygen to survive. When oxygen levels in a compost pile drop below 10 percent, however, parts of that pile become anaerobic -- or deprived of oxygen -- and anaerobic microorganisms takeover. Anaerobic microorganisms produce methane -- a greenhouse gas -- and hydrogen sulfide, which smells like rotten eggs. Anaerobic decomposition also takes much longer than aerobic decomposition. In-vessel systems run the risk of severely limiting oxygen supply by its enclosed nature. Integrating forced air systems eliminates this risk, thus speeding up decomposition.