Biogas Safety first!

Specific requirements
Organisational protective measures
The plant operator must ensure that the only persons
to have access to the hazard area of electrical installations
are those who on account of their professional
training, knowledge and experience are able
to recognise the electrical hazards arising and take
the necessary occupational health and safety measures,
and that other persons are permitted to enter
the hazard area only when accompanied by persons
as described above.
The plant operator must also ensure that all electrical
installations and equipment used are suitable for
use under exposure to the stresses and loading from
the operating conditions and environmental conditions
at the workplace.
17.2. Protective measures in the event of
a power outage
As part of a hazard assessment it is important to
produce as comprehensive a list of potential hazards
as possible for each biogas plant individually
and to determine the necessary protective measures
deriving from that for each specific situation. In the
following the focus is set on the hazards arising and
necessary countermeasures to be taken in the event
of failure of the public power grid.
Technical protective measures
In order to be able to guarantee an emergency power
supply for the biogas plant the first requirement is
fault-tolerant installation (e.g. safe from floodwater
or from substrate if it escapes inside the surrounding
wall).
In addition, the electrical installation of the biogas
plant must be checked for ‘quick-action’ activation
of the agitators and other important components.
In this regard consideration should also be given to
power failures caused by thunderstorms, for example:
if important components such as the programmable
logic controller (PLC), frequency converter,
24-volt power supply units or emergency stop relays
cannot be started quickly, further precautionary
measures must be taken. Ideally, agitators or other
important components can be started in parallel
with the plant control system using a simple installation
without a PLC and frequency converters (e.g.
operation only with plug connector and motor protection).
In relatively large biogas plants with several parts
to the plant (such as gas processing systems) the
gas flare systems are not necessarily controlled by
and supplied from the biogas plant. In such cases it
should be examined how the gas flare system can be
put into operation by ‘simple’ means in the event of
a complete power failure.
In order to be able to guarantee a reliable supply of
power it is also highly important to determine the
power required to maintain the essential processes.
This includes:
Defining all processes that need to continue
running in the event of a power failure
Establishing the length of time for which the
defined processes need to continue running in
order to prevent any danger from arising
Determining the power demand that needs to be
met by an uninterruptible power supply (UPS):
ZZ
information technology
ZZ
alarm systems
ZZ
telecommunications
ZZ
safety lighting, etc.
Determining the total amount of power needed
to maintain operationally critical processes:
ZZ
information technology (all of the above)
ZZ
system control
ZZ
agitators
ZZ
gas-consuming equipment (if applicable
including compressor)
ZZ
lighting
Choosing the correct emergency power strategy is
also important. Various options are presented in
Table 6.
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