the anaerobic digestor behind them. (Photo by Robert
Hubner, WSU Photo Services)
Manure management is a challenge due to the potential harm the waste poses to the atmosphere and to surface water in the form of runoff.
WSU researchers from animal sciences, economics, biological systems engineering and crop and soil sciences – along with scientists from the U.S. Department of Agriculture – have developed and set up the digester Monroe, Wash. It pumps in manure from nearby dairy farms through six-inch buried pipes, significantly cheaper than transporting the effluent by truck.
Anaerobic digestion transforms the manure into three basic and potentially useful products: methane, which can be used in electrical power generation; fibrous organic material, which can be used as a soil conditioner for nursery plantings and home gardening; and a slow-release, crystallized solid fertilizer called struvite.
The highly combustible methane gas from the Monroe digester is burned, the heat energy runs a generator and the electricity created is sold by Qualco Energy http://www.andgar.com/specialty-general-contracting-digester-projects-in-progress-qualco-energy.php to Puget Sound Energy.
“Selling the energy is an immediate benefit for the dairy farmers to help supplement their income in a time when the cost of production within the dairy industry is so high,” said Joseph Harrison, a WSU professor of animal science and nutrient management specialist. “While it isn’t the ultimate answer to the financial problems the dairy farmers have, being able to sell the electricity while still having nutrients to grow crops can help.”
Anaerobic digesters can cost millions of dollars to install, which may not be feasible for many dairy farms. Shannon Neibergs, a professor of economic sciences at WSU, suggested that dairy farmers work together and share costs to construct a digester to serve their region.
The Monroe digester operation is a joint venture between the Sno-King Alliance, Northwest Chinook Recovery, the Tulalip Indian Tribes and local dairy producers. The digester has been funded by a zero interest loan. The research components are funded by multiple grants, including a sizeable USDA conservation and innovation grant.
“Our goal with the anaerobic digester is to expand the number of dairies that are contributing to the operation,” said Neibergs. “It will also continue to serve as a research innovation and demonstration site.”