Cape Town - Municipalities can save 30
megawatts (MW) should their water treatment plants switch off Eskom
and switch on the electricity-generating potential of methane-rich
That's according to Jason Gifford,
spokesperson for the energy division of WEC Projects, a firm which is
implementing South Africa's first biogas to power plant on a
municipal waste water treatment works.
"Biogas is produced as a
by-product of sewage treatment and holds the potential to reduce
waste water treatment plants' dependence on Eskom. Biogas can be used
to fuel gas engine generators to provide a percentage of the
electricity these plants use for operation," said Gifford.
There are 50 major municipalities in SA
that have a waste water treatment plant large enough to operate an
effective biogas plant to produce a possible 30MW.
"As far as energy savings go, a
figure of this size will have a pretty significant impact on both
their own costs and on the electricity provider's drive towards
energy efficiency. Our goal is to make our initial plant a shining
example of how true energy efficiency can be achieved. Once the case
can be effectively made for biogas, we anticipate a number of other
treatment plants will follow this lead," said Gifford.
Biogas is produced by a process known
as anaerobic digestion. This is a natural process involving the
decomposition of organic matter in the absence of oxygen.
Traditionally, sewage treatment plants use this process to convert a
large proportion of the solid sewage sludge, produced in the
mainstream treatment processes into biogas. This reduces the sludge
volume prior to disposal as well as ensuring a stable sludge is
Gifford said due to the massive
increases in the cost of electricity in recent times, it now makes
financial sense to instead use biogas to produce electricity. The
biogas to power plant provides waste water treatment works with an
onsite energy source that should enable them to offset a portion of
the costs of running the treatment plant directly from the grid.
"Part of WEC Projects' role is to
clean the biogas so that it can serve as a fuel. It must be
remembered that following anaerobic digestion, the biogas produced is
what is termed ‘raw fuel'. In other words, it contains water,
hydrogen sulphide and a variety of volatile organic compounds and
siloxanes, which are chemical compounds that can damage the moving
parts in engines. For the gas to be effective as a fuel, it therefore
needs to be conditioned and have these contaminants removed,"
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