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Biogas is a mixture of different gases pro-
duced by the breakdown of organic matter
and is used as a renewable energy source
that exerts a very small carbon footprint.
Global production of biogas is increasing all
the time, however, there are some important
process challenges biogas producers face,
one of these being accurate gas analysis.
The composition of biogas is typically 40-
60 %methane, 40-50 % carbon dioxide, the
remainder being water, hydrogen sulphide,
and other impurities. Biogas producers
need to know what the purpose and use of
the biogas is for end users and they need to
know the exact composition of the biogas.
It’s especially important that they know the
carbon dioxide levels which are usually dif-
ficult to predict.
For example, biogas contains hydrogen
sulphide, which is usually toxic, and it can
be high in biogas that is produced from
animal wastes, such as from chicken, or
from certain vegetables. Biogas is also usu-
ally very wet, and when carbon dioxide and
hydrogen sulphide are mixed with water, it
can be quite corrosive.
For these reasons, it’s usually good to
remove or lower the amount of hydrogen
sulphide, water, carbon dioxide and other
impurities to minimal levels before the
biogas is processed. If this isn’t done, then
the engines that generate electricity from
biogas will experience high rates of corro-
sion, leading to inefficient running of the
engines to produce electricity.
In addition, when the wastes used to
process biogas are varied, the amount of
methane will change due to the behaviour
of the anaerobic bacteria in the digester
used to generate the biogas.
A natural gas chromatograph can help
address these operational and mainte-
nance needs for biogas producers. Plants
require a cost-effective, online gas chro-
matograph (GC) that can measure the bio-
gas composition within a four-minute cycle
time for ongoing real-time analysis. It’s also
critical that the GC is easy to use and has
low maintenance requirements to reduce
time personnel spend on maintenance.
Unlike larger gas processing plants,
petrochemical plants and refineries that
are able to employ skilled personnel for
maintenance of the gas chromatographs,
biogas plants usually will only have techni-
cians who are skilled in the operation and
maintenance of the typical instrumentation
required in the plant. In addition to lowmain-
tenance requirements on an ongoing basis,
the 370XA from Rosemount Analytical also
includes maintainable module technology
that allows operators to easily replace the
Effective gas analysis critical in biogas production
GC module in the field in under two hours,
reducing downtime and repair costs.
Effectivemeasurement of biogas compo-
sition is a critical step to ensure a high quality
product and reduce the risk of corrosion and
potentially dangerous toxic gas leaks, a cost-
effective, easy-to-use gas chromatograph is
a key element in biogas processing.
For more information
go to
http://com-
munity.emerson.com/process/emerson-
exchange
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