Bulldozers weave tirelessly through an asphalt lot on the outskirts of campus. Steam pours from oblong heaps of what might have been animal bedding, food scraps or tree trimmings – a feast for microbes.

The process is called composting. It’s how WSU Waste Management turns organic waste into a usable end product, a nutrient-rich soil amendment, which is used on campus or sold to landscape companies and garden supply stores.

Waste Management is a division of Facilities Operations, the department responsible for maintaining the campus.

Manager Rick Finch said organic material makes up the largest portion of WSU’s “waste stream.” That portion includes practically everything that rots, from pizza crusts to fallen leaves.

In total, Waste Management composts about 10,000 tons of material each year.

A major component is used animal bedding, which comes from several on-campus sources, including the College of Veterinary Medicine and the Department of Animal Sciences.

WSU keeps about half of all its composted material and reuses most of it as animal getting. The other half of composted material WSU does not keep is sold for profit.

“To be able to put that material back under the animals is a great thing,” Finch said.

He said the composting process is so effective at removing pathogens like E. coli and salmonella that the recycled bedding material is safe for animals.

Bill Vertrees, assistant vice president of Capital Planning and Development, said the composting effort is a huge undertaking.

Waste Management gathers the material in large mounds and then composts it using one of two processes.

One process involves long rows of material, called windrows, which are turned weekly by a self-propelled mechanical turner. After eight to 12 weeks, the material is screened for contaminants like plastic and glass.

The other process involves large pipes, which pull air through the mounds. Mechanical aeration is a much shorter process, between 24 and 30 days, after which the material is screened for contaminants.

Naturally occurring bacteria decompose the material and heat the mounds to internal temperatures of about 150 degrees Fahrenheit, hence the steam when bulldozers expose the material to outside air. This occurs without the use of an external heat source.

“Winter and summer can be challenges,” Finch said, noting that moisture is key in the composting process. Too much or too little moisture leads to sub-par compost.

The Compost Facility that appears as little more than a four-acre asphalt lot, is designed to prevent contamination of surface water. Runoff is collected in a series of ponds, which are emptied during the summer, when the surrounding fields are dry enough to absorb water.

Finch said WSU is able to participate in composting because it has many sources of organic waste, like the agriculture and animal sciences departments.

“Those are things a liberal arts school wouldn’t deal with,” he said.