Perth
RESIDENTS of Perth, Western Australia, may soon breathe easier, thanks to a
proposal to turn sewage sludge from a local waterworks into a fuel similar to
diesel.
Environmental Solutions International, a company based in Perth, is awaiting
final approval from the Western Australian government for the A$19
million (拢10 million) oil-from-sludge plant. It is due to be built at a
treatment works in the suburb of Subiaco by the end of next year.
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At the moment, the water authority treats some sludge in open digester tanks,
which can generate unpleasant smells. The new facility will be based on ESI鈥檚
Enersludge process, which takes place in sealed units. It will be the world鈥檚
first commercial Enersludge plant.
Enersludge converts carbonaceous material such as sewage sludge into
petroleum-type products. The conversion takes place in two anaerobic
reactors.
The first chamber is a large oven, in which dried sludge鈥攂etween 90 and
95 per cent total solids鈥攊s heated to 450 掳C. This drives off up to
half the weight of the sludge as vapour.
In the second chamber, trace metals in the sludge act as catalysts. They
convert organic compounds in the vapour and char, such as proteins and lipids,
into hydrocarbons.
As well as the diesel-type oil, the process produces char, noncondensable
gases and water contaminated with acetic acid. These can be used to generate hot
gas to heat the sludge drier and the Enersludge reactors. The oil can be burnt
in a diesel engine to provide on-site power.
Roger Nicholls, one of Western Australia鈥檚 water ministers, says the
government could save about A$700 000 every year by generating
electricity at the site. But Densi Glennon, managing director of ESI, insists:
鈥淭he issue is the processing of sludge, and doing that in a way that will be
essentially odourless.鈥�
