The Management and
Disposal of Dairy Manure
DONALD E. PROCTOR, Associate Sanitary Engineer
College of Engineering Research Division
Washington State University
Pullman, Washington
INTRODUCTION
Dairy manure, like many other materials regarded as wastes, can be either a
liability or an asset depending upon several factors. Manure is of significant economic
importance to the practicing dairyman in any case. In the state of Washington
alone, approximately 220, 000 producing dairy cows excrete over 8000 tons of
urine and feces each day.
A dairy operation of 200 Holstein cows (not at all uncommon today) represents a manure management problem of around 3000 tons per year. Assuming that
good-versus-poor management could reduce the handling costs by only as much
as $0. 50/ton, there is a $1500.00 incentive for good management. Further, if
the fertilizer value is recovered and utilized as a result of good management instead of finding its way into surface or ground water, an additional incentive appears for the good manager. The realized fertilizer value does not always equal
the handling costs involved in manure utilization as fertilizer. In many of such
cases, it may still cost less to utilize manure on fields than to provide any alternative means of disposal. The choice is not simply whether to spread, or not
to spread, the manure on fields. The choice is whether to field-spread the manure or develop another method for avoiding the problem of accumulation near
the dairy. Of course one method of avoiding the problem of manure accumulation is to sell the farm and herd to someone else. This option is more attractive
than the option of operating with a net economic loss.
Aside from the economic plight of the farmer, why should society be concerned with manure management? Farmers have long produced milk, meat, and
eggs but we havent been overly concerned with this problem in the past so why
be concerned now? The changes that have brought about a need for concern may
be listed as follows: 1) More people want more livestock - derived products --
therefore more livestock: 2) Specialization of farm operations leads to concentration of manure production-, 3) Confinement rearing leads to further concentration of manure production and significant changes in manure characteristics;
4) Cheaper commercial chemical fertilizers reduce the agricultural demand for
manure for fertilizer; 5) Urban sprawl and farm area encroachment brings more
people into close contact with the environmental problem-, and 6) Higher aesthetic standards lead to more concern even if the problem were not increased.
While all of these changes are significant, confinement rearing is probably
most significant. Large herds of dairy cows are held continuously on paved areas
with 150 to 200 sq ft of area per cow. All feed, forage, and water is brought to
the cows. No manure or urine is defecated directly on the fields. Silage diets
and the lack of infiltration results in a composite manure of higher moisture content and fluid consistency. Little bedding, if any, gets mixed in with the manure.
Rain water may add to the waste volume.
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