Beltsville, Md.-An Agricultural Research Service scientist has found that algae already being eyed for biofuels could be put to work right away to produce nitrogen and phosphorus from livestock manure and provide a way to reduce farmland runoff into the Chesapeake Bay. In 2003 Microbiologist Walter Mulbry at the ARS Environmental Management and Byproduct Utilization Research Unit here in the Chesapeake Bay watershed started setting up outside dairy barns four 100-foot algal turf scrubber raceways covered with nylon netting where the algae could grow. A submerged water pump at one end circulated a mix of fresh water and raw or anaerobically digested dairy manure over the algae. Within two-to-three weeks the system supported thriving colonies of green filamentous algae. For three years, from April until December, Mulbry and his partners harvested wet algae every four to 12 days, dried it, and then analyzed the dried biomass for nitrogen and phosphorus levels. His results indicate that the system recovered 60 to 90 percent of the nitrogen and 70 to 100 percent of the phosphorus from the manure effluents. They also calculated that the cost for this capture was comparable to other manure management practices – around $5 to $6 for each pound of nitrogen that was recovered, and around $25 for each pound of phosphorus that was recovered.
Transparency Across the Fertilizer Value-Chain