Environmental Engineering Reference
In-Depth Information
1.4
Health, safety and risk assessment
Biogas plants are technical facilities that process products and by-products
from farming and food processing, different types of organic waste and
energy crops. Digestion produces biogas and a digested product that, in
most cases, provides a valuable input as fertilizer. Biogas is flammable but
not explosive; an explosive environment can develop, however, if methane is
present at very low concentrations of 6-12%.
All mechanical and moving parts of the biogas plant can pose hazards
and the uncontrolled escape of biogas or fermentation products is another
potential hazard source. The applicable regulations for device and product
safety as well as health and safety must be observed during the construction
and operation of a biogas plant. Depending on the size, type and
environment of the plant, different countries have established sets of rules
for the technical safety of plants which, at least in part, are prescribed by
European directives. Biogas plants built primarily for the treatment of
organic waste from industrial processes or households are subject to the
regulations in effect for industrial waste treatment plants. Plants processing
digested sludge from waste water treatment plants come under the waste
water treatment regulations. Many biogas plants on farms are covered by
rules applying to agriculture or new regulations are enacted specifically for
such plants.
The target for every biogas plant must be to ensure the highest possible
level of safety for humans and the environment. It is important that safety
regulations can be understood by those who are expected to observe them
and that they can be applied in the applicable economic framework. In light
of this, the rules for industrial waste treatment plants can and must be
different from those applying to the construction and operation of biogas
plants on farms that process primarily manure and renewable primary
products.
Experience in Germany, where altogether about 7000 biogas plants were
in operation in 2011, most of them in a farming context, has shown that
most accidents were due to mistakes on the part of operators. In many cases,
the accident was caused by deflagration or explosion of escaping biogas.
Rarely was an accident due to the toxic action of hydrogen sulfide present in
untreated biogas or in the feeding area of the biogas plant. There was hardly
a case in which the technical rules for the construction of biogas plants had
not been sufficient or had not been observed - it was rather a question of
wrong handling. The operators of biogas plants must therefore be trained
thoroughly. Another German experience is that fewer accidents happen
during normal operation than happen during construction, start-up or
maintenance of a biogas plant. Again, personnel doing the work must be
trained and made aware of the risks involved.
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