This photo shows the methane blankets, accentuated in bright green, extending from the Earth’s poles. Of all greenhouse gases, methane seems the most innocuous — yet it traps 23 times more heat in the atmosphere than does CO2. Atmospheric levels of methane have increased more than 150 percent since 1750 — and could double again by 2050. (Photo by Goddard Institute for Space Studies, NASA)
 
Traditionally, dairies have used open lagoon systems to handle manure storage — resulting in large emissions of methane and nitrous oxide. According to Shulin Chen, professor in biological systems engineering, about 65 percent of atmospheric methane is attributable to agriculture, with a large portion arising from the manure of dairy cows. As part of the Climate Friendly Farming project, Chen is investigating novel ways to process manure using closed-system anaerobic digesters.
At the WSU Knott Dairy, Chen is testing a prototype digester that uses bacteria to break down organic matter in the manure. The process releases methane, which his team hopes to collect and use to generate electricity.
The manure is also separated into liquid and solid components that can be processed into byproducts such as fertilizer and fiber. The fiber has potential as a soil booster, for animal bedding or as a substitute for peat moss in the horticulture industry. The team also is studying ways to trap and use the waste heat and CO2.
Ideally, Chen said all dairies should have anaerobic digesters — but high cost is a limiting factor. Government subsidies could overcome that hurdle, but the more likely scenario would be the creation of a carbon credit market — whereby farmers could funnel methane into electricity in exchange for green tags and carbon credits.
Chen also is looking for ways to streamline digester technology in hopes of making it more cost effective for farmers. In addition, his team continues to develop value-added byproducts to improve economic returns.
Chen said farmers are excited about the multiple benefits that anaerobic digesters can provide — especially the ability to transport nutrients off the farm. With lagoons, excess nitrogen is emitted as ammonia — contaminating air and water quality. Using a digester allows nutrients such as nitrogen to be concentrated into a solid form and transported off the farm for “recycling” as chemical fertilizers.