A proposal for solid and liquid waste treatment facilities at Longue Hougue

July 26th, 2011 by Dick Bilborough

  • Longue Hougue is the dedicated location for a waste park and a sewage treatment utility.
  • Outline planning permission for most waste technologies already in place.
  • The proposal would service every household and business in Guernsey.
  • Requires the approval of the Assembly of the States of Guernsey.

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  • Existing Guernsey businesses dealing with scrap metal, cardboard/paper, dry solid waste are efficient by any standards and have efficient collection services.
  • There is no point in seeking foreign competition.
  • Guernsey businesses are capable of dealing with the outstanding waste problems.
  • The solution should be Guernsey-funded, Guernsey-managed and Guernsey-operated
  • The outstanding problem is food waste before and after the event of human digestion.
  • Solution to the end product of human digestion – sewage treatment works, for which long established technology.
  • Food waste pre-consumption requires solution.

Particular Constraints on Organic, Food and Wastewater Treatment Methods that are Peculiar to Guernsey

  • Majority of land area is rainwater catchment.
  • Application to soil of residual treated waste and by-products inhibited.
  • The Mont Cuet, the only landfill/landform, will close in the near future.
  • Co-mingled food waste requires separation and treatment.
  • Zero tolerance for incineration by the majority in Guernsey.
  • Important to ban disposal of organic wastes to Mont Cuet.
  • But first a treatment facility required to which the waste can be diverted.
  • Source separation and separate kerbside collection are only possible if there is a treatment facility.
  • The treatment facility must produce minimal residual wastes.
  • Residual waste cannot be applied to land.

Food waste arises broadly from three separate categories:

  • Catering Waste
  • Source Separated Waste
  • Co-mingled Black Bag Waste
  • A solution is anaerobic digestion with amendments to meet the Guernsey constraints and requirements.
  • Anaerobic digestion susceptible to contamination by inert material which can stop the process with costly consequences.
  • Food waste has to be separated from contaminants before entering dedicated digesters.
  • Front end separation of the waste from contaminants essential.

Stage 1 – A wet Materials Recycling Facility (MRF)

Stage 2 – Twin Separation Pre-treatment Filter Tanks with macerator pumps

Stage 3 – Anaerobic Digester

Stage 4 – Dewater. Result: Sludge Cake


Dr Christopher Rowlands

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  • Established conventional sewage treatment process
  • Extensively used for most communities in UK
  • Sludge Treatment Facilities indoors
  • Power Generation indoors

An empty settlement tank (please click image to expand)

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The images above show typical aeration tanks and a typical digester.

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The image above shows a centrifuge installation and a typical external power generation plant.

Sewage treatment process (click diagram to expand)

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Dick Bilborough

  • The STW and the Food Waste Treatment Plant are located in close proximity to exploit synergies and avoid duplication of investment.
  • BUT the plant will have built in ‘redundancy’ which in this context means that the risk of downtime is fully covered.
  • For example – twin digesters, twin dryers.
  • Sludge cake is dried to form a dry 90°C fuel.
  • Dried fuel powers boiler.
  • Boiler provides heating for digesters, buildings and offices.
  • Boiler produces steam to power steam turbine to produce electricity.

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Fuel and boilers (click image to expand)

Waste Minimisation and Capacity

  • The sewage sludge will be reduced to circa 2 tonnes of ash per week .
  • Calculating food waste involves a significant degree of guess work.
  • What percentage of food waste is co-mingled in black bag in Parish collections?
  • What tonnage should we allow for source separated waste when it eventually occurs?
  • Plant capacity is designed for a minimum of 5,000 tonnes food waste which will reduce through the process to circa 1 tonne of ash per week.

How is this to be achieved?

  • Requires the consent of the Assembly of the States of Guernsey.
  • A long term commercial lease of the Longue Hougue site.
  • Agreement on a Joint Venture between the States and the Company.
  • The Company seeks close involvement of key Officers in the States Departments relevant to the development of the JV project including the input of existing expert management.

How much will it cost?

  • Development of the Longue Hougue site, treatment plants, infrastructure, buildings – circa £65 million.
  • £65million can be funded privately.
  • A Joint Venture Company in which the States of Guernsey owns 20% of the equity.
  • 10% to key stakeholders – all the householders and businesses whose waste products would be serviced by the facility
  • It is proposed that the financial structure of the Company will be £35million equity plus £30million loan stock.
  • The ordinary share capital and loan stock to be listed on the Channel Islands Stock Market.
  • Target commissioning date for the project 2014.
  • The Company, it’s Directors and Advisors have no involvement or investment in any of the suppliers or technology.

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(click on the image to download the complete PowerPoint presentation as a PDF file)

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