Health and environmental hazards associated with the use of producer gas
A review of the different types of hazards and environmental impacts of producer gas operation has been published by Kjellstrom (23).
Toxic, fire and explosion hazards are the main categories.
An important constituent of producer gas is carbon monoxide, an extremely toxic and dangerous gas because of its tendency to combine with the haemoglobin of the blood and in this way prevent oxygen absorption and distribution. A summary of the effects caused by different concentrations of carbon monoxide in the air is given in Table 2.9.
Fortunately normal producer gas installations work under suction, so that even if a minor leak in the installation occurs, no dangerous gases will escape from the equipment during actual operation. The situation is different however during starting-up and closing down of the installation.
During starting-up the gas is generally vented, and it is necessary to ensure that the gases produced cannot be trapped in an enclosed room. As a rule a suitable chimney will provide sufficient safety.
During closing-down of the installation a pressure buildup in the gasifier will occur, caused by the still hot and pyrolysing fuel. As a result gases containing carbon monoxide will be released from the installation during a relatively short period. It is because of the danger from those gases that it is generally recommended that a gasified installation be located in the open air, if necessary covered by a roof.
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Table 2.9 Toxic effects of different concentrations of carbon monoxide in the air
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There has been some dispute, deriving from Swedish experience, whether chronic poisoning can occur as a result of prolonged inhalation of relatively small amounts of carbon monoxide which give no acute effects. It-seems that the issue now has been resolved: no chronic symptons can occur through carbon monoxide poisoning.
However this does not mean that the symptoms mentioned in Swedish literature (tiredness, irritability and touchiness, difficulty in sleeping) did not result from prolonged exposure to producer gas. There is a possibility that some other compound(s) in the gas are responsible for the symptoms.
The above stresses again the importance of placing stationary installations in an open environment as well as of taking care to avoid close contact with the gases during the starting-up and closing-down phases.