Aerated static piles

Multiple methods can be used to create compost, but all involve four basic ingredients. First are high-carbon materials such as mulch, chipped wood, dried leaves, shredded paper and grass clippings. We tend to call these “browns.” Second are highnitrogen materials like carrot tops and leftover salad — fresh food waste we call “greens,” regardless of color. The other two ingredients are water and air/oxygen.

Much of the water in our piles comes from the food waste itself — many vegetables are composed of more than 90 percent water. Air/oxygen is all around us, but to activate the aerobic microorganisms already existing in food waste, accelerating the flow of oxygen, especially in the middle part of the pile, is crucial.

In home-scale piles, this may be done by turning the pile with a pitchfork. In commercial-scale systems, the long, tall piles are called windrows, and turning them can be done with a tractor or a specialized machine called a windrow turner. Alternately, and more efficiently, air can be blown into the windrow, which is what Reunity Resources is doing. The pile is therefore static (not moving or being moved). It is aerated instead via a simple fan and pipe system.

Before making a windrow, we lay down a large perforated pipe with a cap on one end and a fan on the other. The fan operates on a timer to inject air intermittently, 24/7. The cap on the other end forces the air up through the perforations, thus aerating the pile from the inside out.

Given this efficient method of aeration, the microorganisms at play in the natural process of composting are highly active. The compost windrow reaches internal temperatures ranging from 130 to 160 degrees Fahrenheit, allowing even dense materials like meat and bones to compost effectively.

The compost cooks on the aeration system for approximately 30 days and then cures for another 30 days, gradually cooling to ambient temperature. It is then screened and sifted and prepared for sale or use.