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Further separation concentrates nitrogen and phosphorus in the solids. The liquid "tea water" contains mainly dissolved solids, including ammonia and potassium.
THE mass of manure produced on American livestock farms - totalling about one billion tons per year - is both valuable and a nuisance. On one hand, manure is an important source of nutrients and organic matter to grow crops and maintain healthy soils. On the other, it's smelly, of potential concern for air and water quality and, when produced in excess of a farm's needs, difficult and expensive to transport and apply.
Interest in exploring technologies that enhance manure's benefits while reducing, or even eliminating, the problems associated with it, is high in the $35.5 billion/year dairy industry. The sector is under pressure to produce more milk and cheese for a growing population, while that population sprawls across farmland, leaving less space to spread manure. "There is a tremendous opportunity to generate environmental and economic benefits from manure by-products, but further innovation is needed to develop more effective and affordable technologies," the U.S. Environmental Protection Agency (EPA) states in a background paper for its ongoing Nutrient Recovery Technology Challenge.
Reducing complaints and environmental risks is crucial to giving dairy farms a "social license" to operate, according to Newtrient LLC, a Rosemont, Illinois company founded by 12 milk cooperatives representing nearly 20,000 U.S. dairy farmers, to develop nutrient recovery technologies. These technologies separate manure's components into as many useful and benign products as possible. Three examples from dozens of U.S. and Canadian dairies engaged in some form of advanced nutrient recovery are:
* Edaleen Dairy Farm in Lynden, in northern Washington State, anaerobically digests manure from 1,800 Holstein dairy cows to produce energy, bedding for the stalls, nutrient rich cakes that can be transported to distant fields, and a liquid residue called tea water that, within limits, can fertilize and irrigate feed crops.
* The massive Prairie's Edge Farm in Fair Oaks, Indiana, goes a step further with the manure from its 15,000 Holsteins. It ships the nutrient cakes to a facility where it is processed to create a series of custom products.
* SeaBreeze Farm in Delta, south of Vancouver, British Columbia, has 350 Holstein cows and is seeking ways to make...