manure storage systems have come into prominent use in recent
years. Many dairy, beef and hog operations (and to a limited
extent poultry operations) now use liquid manure systems as
a fast and economical method of handling animal wastes. These
systems, particularly if they are incorporated into the barn
construction, may pose a serious hazard because of gases produced.
Decomposing animal manure gives off a variety of gases including
hydrogen sulphide, carbon dioxide and methane. Of all these
gases, hydrogen sulphide or more commonly called manure gas,
is the most dangerous. Hydrogen Sulphide (H2S) has
been responsible for many animal deaths as well as occasional
Sulphide is formed as a result of decomposing animal manure.
The decomposition process begins as soon as it is excreted by
the animals. Micro-organisms utilize the manure to synthesize
new cellular material and to furnish energy for synthesis. This
process takes place with or without oxygen. However, the type
of microbes, and the type of gases that are produced, are dependent
on the type of environment in which degradation takes place.
In anaerobic conditions (without oxygen), typical of most liquid
manure systems, hydrogen sulphide will be given off.
sulphide is produced continuously in all un-aerated manure
storage systems, including shallow barn gutters, underground
storage tanks or outside manure holding ponds or lagoons.
Depending on temperatures and other factors, the rate of release
of the gas is slow in undisturbed storage.
sulphide is a clear, colourless gas that can be identified in
relatively low concentrations, by a characteristic "rotten-egg"
odour. Hydrogen sulphide is approximately 20 percent heavier
than air, with a specific gravity of 1.19. Hydrogen sulphide
odours can be recognized in concentrations of less than 1 mg/kg
(air). The odour of hydrogen sulphide will increase as the gas
becomes more concentrated. However, in concentrations of 150
or greater mg/kg (air), a person's ability to detect the gas
is affected by temporary paralysis of the olefactory nerves
in the nose. Owing to this unique property of Hydrogen sulphide,
relying totally on the sense of smell to warn against the gas,
can be extremely dangerous. In high concentrations, the ability
to smell the gas is lost instantaneously, the disappearance
of the odour could mean that the gas concentrations have increased.
sulphide is classified as a toxic chemical, in high concentrations
it will lead to almost instantaneous poisoning and death. High
concentrations will result in the complete arrest of respiration.
A person over come by this gas should promptly be removed from
the contaminated area and given immediate artificial respiration.
to lesser concentrations may result in nausea, stomach distress,
belching and coughing. Moderate concentrations may result
in eye irritation.
hydrogen sulphide is heavier than air, the gas has a tendency
to accumulate on the surface of the manure. Over a period of
time, the undisturbed accumulation of the gas, along with a
rising level of liquid manure in the storage system, may force
the gas above floor level. When this happens animals are usually
doomed. Above ground air currents may also result in localized
concentrations of the gas, this usually explains why livestock
losses occur in certain areas of a particular barn.
danger of exposure to hydrogen sulphide exists during agitation
and pumping. Clean out during the fall months after several
months of warm temperature storage accelerates gas production,
or clean out after a prolonged period of time increases the
potential danger. During agitation, hydrogen sulphide is released
from the manure in the same manner as carbon dioxide is liberated
after shaking a carbonated soft drink.
following precautions are essential to the safe management of
a liquid manure system located in a livestock building:
no circumstances should anyone enter a liquid manure pit
without wearing a self-contained breathing apparatus, even
if the pit is empty. Use a life line that is connected to
someone outside the danger area.
allow the manure pit to fill completely. Allow 1 to 2 feet
of air space to accommodate concentrations of gas.
possible, lower the level of liquid manure in the storage
facility before commencing agitation. This will further
reduce the possibility of gas being forced above floor level.
the agitator below the liquid surface. Gas will be released
in greater volumes if vigorous surface agitation occurs.
strong ventilation during pumping and agitation. The building
interior should be off limits to people, and if possible,
animals should be evacuated.
of the dangers presented by the agitation and pumping operations,
these procedures should involve two people, connected by
a life line, with one person always outside of the danger
with your physician if you have been exposed to hydrogen
sulphide in concentrations severe enough to cause irritation
to the respiratory tract.
The danger of hydrogen sulphide in spreader tanks is as great, or greater than that of a liquid manure pit. Under no circumstances should a spreader tank be entered without using a self contained breathing apparatus and a life line attached to someone outside of the danger area.
OF HYDROGEN SULPHIDE *
American Industrial Hygiene Association, 1962.
AND CONSTRUCTION OF NEW FACILITIES
factors should be taken into consideration if you are considering
incorporating a liquid manure system into a new building:
RESPONSE OF ADULT HUMANS TO HYDROGEN SULPHIDE **
manure pit pump-out openings should be located outside the
building, thereby eliminating the danger of working in a
manure storage should be separated from the livestock buildings.
Connecting drains, gutters and channels should be fitted
with gas traps, or some other means, to prevent gases from
re-entering the building.
liquid manure collection pits should be kept to a minimum
volume and divided into small compartments to eliminate
the need for agitation.
Mg (H2S)/1 Kg (Air)
of Respiratory Tract
Source Nordstron, G.A.: J.B. McQuilty: "Manure
Gases in the Animal Environment." University of
Alberta - 1976.
Publication #: F-006
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