A mobile system for removing phosphorus from cow manure may offer dairy farmers greater flexibility in where, when, and how they use the nutrient to fertilize crops.
The idea behind the Manure Phosphorus Extraction System (MAPHEX) is to remove phosphorus and concentrate it in a form easier to manage, says Clinton Church, an Agricultural Research Service (ARS) environmental chemist.
“Some farmers with plenty of land may need to drive 20 miles or more to reach some fields,” says Church. “That makes transporting large volumes of manure uneconomical (or impractical), even if the crops there need phosphorus.”
Working with Pennsylvania State University collaborators, Church and his colleagues developed and tested MAPHEX as a way farmers could “mine” phosphorus from their manure and market it as a value-added product.
To do this, the team mounted an auger press, centrifuge, vacuum-filter unit, and other components atop two trailer beds so the entire system could be driven to a farm and operated onsite on a daily or rotational basis.
MAPHEX works in three stages, each removing progressively smaller fiber particles and other phosphorus-containing matter from the manure. In addition, there is a chemical treatment step between the last two stages to convert dissolved phosphorus into a filterable particle. Water extracted from the manure is retained on the farm; it contains most of the manure’s nitrogen.
MAPHEX works quickly. In about 10 minutes, it can extract 99 percent of the phosphorus from 250 gallons of manure. Additionally, it removes odor from the manure.
The fiber and other phosphorus-containing particles exit the system as concentrated solids, which can be transported for use off-farm or sold to nurseries. Solids from MAPHEX’s first treatment stage could also be sold as cow bedding.
The MAPHEX team will begin demonstrating a full-scale version of its system on a working dairy farm this spring.
Jan Suszkiw is with the U.S. Department of Agriculture’s Agriculture Research Service office.