Conversion of Cattle Manure into High Quality
Protein
M. B. ETTINGER, Senior Contract Research Specialist
Dow Chemical Company
Midland, Michigan
L. L. WADE, Senior Research Entomologist
Dow Agricultural Research
Lake Jackson, Texas
INTRODUCTION
The problem of coping with the growing volumes of animal manures is a highly
important sector of the solid waste problem which has received relatively nominal
amounts of attention. The same problem is a growing portion of the water pollution
control problem and animal manure disposal probably has received more attention
from people primarily concerned with water pollution. Wherever 10,000 or 100,000
cattle exist in close confinement, there clearly is a vicinal insect and odor problem.
These problems presented by cattle manure are presently severe and promise to
grow as the evolving practice of the beef producing industry leads to increasingly
large feed lots. The commonly used factor for estimating the manure per animal is 10
tons per head per year. If the present population of animals is estimated at
120,000,000, one arrives at a figure of 1.2 billion tons of manure per year. Study of
data assembled in a 1969 OST report (1) indicates that cattle manure is
approximately one third of all the solid waste produced in the U. S. One can estimate
that it contains over twice as much phosphorous as all the domestic sewage in the U.
S.
According to the "Economics of Clean Water" (2), there were 176 feed lots in
1968 with a capacity of over 8,000 cattle. 19 of these lots had a capacity of over
32,000 animals. This statistic may be compared with a report (3) that there were ten
lots with a capacity in excess of 32,000 animals in 1962.
The animal on the range distributes its manure so that very little problem is
presented in the warm months. However, in northern climates, the animal must be
fed during the winter when pastures are snow covered. Manure which is deposited by
the animal or spread by a cattle farmer on top of snow on frozen ground is likely to
reach surface waters during the period when snow melts off. It may also affect
ground water properties when concentrated.
The procedures for feed lot management now require spreading the manure, or
in some cases, the anaerobic lagoon followed by an aerobic lagoon may be used for
waste treatment. Cattle manure does not lend itself well to conventional combustion
disposal. It is initially wet and cannot be dried without causing noxious odors, and
evolving some ammonia which must be absorbed. The dried manure when burned at
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