Power solution for municipalities

2012-08-14 13:34

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 biogas.

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 disposed of.

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," said Gifford.


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