GoKawiilA series of large metal contraptions separate most of the solids from the manure wastewater.
JOE PROUDMAN/UC DAVIS
It was mid-March but already above 80 °F in the Central Valley, which is walled off from the cool Pacific air by the coastal mountain range. Knee-high oat stalks swayed in fields that stretched to a line of almond trees in the distance.
Agueda, who graduated from Fresno State last year and now helps lead the operations on the farm, met me and UC Davis’s Mitloehner, who has studied the effects of vermifiltration, along the side of the barn. (UC Davis has no affiliation with the farm, but the university helped facilitate the meeting.)
He led us along dirt lanes as he explained the workings of the vermifiltration system, which they began using in October 2024.
As before, a flush system washes manure from the floors of the barns into a large collection pit. But now a set of pumps funnels it through a series of large V-shaped metal contraptions standing on a nearby concrete pad, where mechanical screens separate most of the solids from the water.
A conveyor belt takes away the solids, which the farm composts for cow bedding or fertilizer. The remaining liquid moves through a system of pipes, first to settling ponds and then on to an irrigation system suspended above the vermifiltration beds. The long, tubular structure runs over the mounds on wheels set in gravel tracks, wetting the wood chips as it goes. The worms and various microbes residing in the biofilter then set to work consuming much of the remaining solid material, according to BioFiltro.
An irrigation system sprinkles wastewater onto the vermifiltration beds. JOE PROUDMAN/UC DAVIS
“Once the water is sprinkled on top, it takes about four hours from beginning to end for it to percolate through and drain to the end,” Agueda says.
He then defers to Mitloehner to explain the science of what happens as it does, adding, “I’m just the dairyman.”
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