May Help the Environment
By Linda McElreath
February 14, 2003
Disposal of animal manure is one of
the biggest problems facing agriculture today. Now, scientists with the
Agricultural Research Service may have
found a way to convert some types into a material that can be used to help keep
the environment clean.
Currently, animal waste is valued at between $3 and $10 per ton, and most of
it is used as a fertilizer. Unfortunately, when added to soil, a buildup of
nutrients--namely nitrogen, phosphorus and potassium--can occur, especially if
it's applied repeatedly to the same area. This can lead to non-point source
pollution runoff into rivers and streams as well as nitrogen leaching into
shallow groundwater, which has caused some states to introduce legislation that
would limit such applications.
Isabel Lima, a chemist in the
Utilization Research Unit at ARS'
Regional Research Center in New Orleans, La., has discovered a potentially
less detrimental way to utilize animal waste. She has found a way to convert it
into activated carbons, which soak up unwanted pollutants and can be used for
Right now, bituminous coal and coconut shells are the two materials most
commonly used by U.S. manufacturers to make activated carbons. However, coal is
an expensive and nonrenewable resource, costing between $60 and $80 per ton,
while coconut shells are not readily available here.
So far, Lima has focused her studies on poultry litter, which is inexpensive
and available. When pelletized and activated under specific conditions, the
litter becomes a highly porous material with a large surface area. In early
tests, these carbons performed very well in adsorbing copper, which suggests
they may do well as a wastewater filter for other metal ions. Their adsorption
rate may also make them more cost effective than carbons currently on the
This technology could provide farmers with an acceptable way to beneficially
use their animal manure, especially in environmentally sensitive areas with
dense poultry populations, such as Maryland's eastern shore.
Lima will be presenting her findings at the
Joint Residuals and Biosolids Management Conference and Exhibition in
Baltimore, Md., Feb.19-22.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.