Western Isles Integrated Waste Management Facilities

In March 2005, following competitive tender, Earth Tech were awarded the contract by Comhairle nan Eilean Siar (Western Isles Council) to design and build two integrated waste management facilities. These new facilities will act as the cornerstone for the Council’s municipal waste management service delivery, allowing it to not only meet but exceed the challenging targets for recycling and landfill diversion that have been set by the Scottish Executive. This will ensure that the Western Isles is able to play its part in helping Scotland meet the requirements of the European Landfill Directive.

Residual waste is mechanically screened, firstly to separate out metals for recycling, but primarily to produce an organic-rich fraction. This is then treated in a series of HotRot composting vessels to produce a low-grade soil conditioner for use in landfill restoration. Both the AD and the In-Vessel Composting system are fully compliant with the Animal By-products Regulations.

The main waste treatment facility, situated in Stornoway on the Isle of Lewis, will be the first plant in the UK to incorporate anaerobic digestion of source-separated biowaste (food, paper and garden waste) on a commercial scale. The Linde dry-digestion technology lies at the heart of the process. The biogas produced is used to generate up to 2 million kWh of electrical power annually for export to the local network, whilst the solid digestate is matured to produce a high-quality compost for local use.