Sawdust and woodchips are used as bulking agents. The composting facility is a three-acre enclosed building with a concrete floor. A turning machine is used to stir windrows daily. Downdraft aeration is used and air exits through a biofilter consisting of compost, bark, and woodchips in which microorganisms destroy compounds responsible for odors. The vessels consist of concrete bins with false floors or air plenums installed in the bottom.
Height is limited to about ten feet.
Excess height leads to excessive settling. Compost that is too dense cannot be properly aerated. The width is determined by design requirements for turning and loading equipment. A 20-foot width has worked well in many units but some are 100 feet wide. The length of the vessel can be based on anticipated capacity, available space, and turning and loading requirements.