The organic waste is formed in long piles approximately eight feet high by about 14 feet wide. The long piles are called windrows. The piles are turned every so often to aerate the pile and speed decomposition.
Aerated static pile composting
The aerated static pile utilized blowers and a network of pipes beneath the pile to keep it aerated. This eliminates the need to turn the piles, thus providing more flexibility on pile dimensions.
This process moves the organic material into a vessel that could be anything from a concrete bunker to a plastic tank. By containing the material, the operator has greater control over the process.
Anaerobic digestion is done in-vessel but eliminates the aeration portion. Instead, the process relies on anaerobic microorganisms to degrade the material. This process results in the generation of methane which is then utilized as a fuel.