The old saying that “only the rocks live forever” reminds us that all of our man-made inventions have an end-point. That includes animal waste lagoons.
Most of today's large-scale, animal-feeding facilities are too young to have reached the end of their useful life, yet at some point they will. And, their expiration may pose quite an expense for animal feeders who use them.
An estimate from North Carolina says it costs an average of $43,000/acre of lagoon surface to haul the wet sludge and apply it to land elsewhere. Other states show similar figures.
North Carolina State University (NCSU) is studying an alternative closure method that shows promise. Researchers say unneeded lagoons might be covered with soil and planted to trees to help draw out the moisture, as well as the nutrients. The process, known as phytoremediation, is essentially the same process being used on many municipal landfills across the U.S.
The two lagoon sites in the research project are planted to hybrid poplar trees provided by Ecolotree, an Iowa company specializing in reclaiming landfills and contaminated sites.
Native species of trees may also be considered, but have not been yet planted, says NCSU agricultural engineer Frank Humenik.
Monitoring wells at the sites check for seepage of the nutrients away from the lagoons.
Only one year of data has been drawn from the site, Humenik says, but the second-year data was being gathered at press time. If the process is successful, it could be vitally important as North Carolina is considering the elimination of all lagoons, pending the outcome of a large research project on alternative waste handling technologies.