All of the of sewage sludge from the city Glasgow, Scotland (population: ~700,000), approximately 54,000 tonnes, is transported to the Daldowie Sludge Treatment Centre. The centre was built at a cost of £65 million to dry sewage and covert it to pellets. Twelve decanter centrifuges dewater the sludge to 28% dry solids followed by six drum drying lines, (with a capability to evaporate a 22,000 litres of water per hour) producing a sludge of less than 10% moisture (Andritz, 2000).
Scottish Power co-combust the pellets with coal in its Longannet coal-fired power station, a 2.4 GW coal fired power station, the second largest coal fired power station in the UK. The sewage pellets have a similar energy value to brown coal and provide 7% input for one of the four 600MW burners, enough to power 30,000 homes.
| Industry Sector | Specific Industry |
|---|---|
| water utility sector |
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| power utility sector |
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Forth Valley, Scotland, United Kingdom
Economic |
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Environment |
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Social |
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At the time of writing, legal problems are endangering the synergy’s continuation due the UK’s adoption of the 2000 Waste Incineration Directive. This legislation removed the distinction between hazardous and non-hazardous waste (previously the category of sewage sludge) and introduced much stricter emission standards. A ruling in December 2002 means Longannet sewage pellets are considered ‘waste’ under the Directive. The cost for Scottish Power to make Longannet compliant is estimated to be between £100-400 million.
25 November 2005