The principal heat source for the Lerwick District Heating Scheme in Shetland, the Energy Recovery Plant is a substantial green corrugated iron construction located at Green Head, a mile (1.5 km) north northeast of Gremista and 2 miles (3 km) north northwest of Lerwick town centre. Beginning operations in 1999, this waste-to-energy plant comprises a moving grate furnace which consumes around 22,000 tonnes of municipal waste per annum. This comprises all of Shetland's combustible rubbish, together with waste imported from Orkney, from shipping and from oil installations offshore. On average, it generates 6.5 MW of heat output and operates 24-hours per day, seven days per week, with breaks in operation only for servicing which amount to approximately 30 days per year, usually in the Spring and Autumn. Water is heated to 115°C and pumped around a 19-mile (30-km) heavily-insulated pipe network laid around the town. It returns to the plant at a temperature of 55°C to be reheated. Flue gases are cleaned to high environmental standards and then expelled through a slender 46-m (150-foot) high chimney. Metals are extracted and recycled from the furnace ash and the residue is then sold for landfill cover.
Operational since 1998, this is one of the first district heating schemes in the UK supplying heat generated from municipal waste. The District Heating Scheme provides low-cost heating to around 1100 domestic, commercial and public-sector customers throughout Lerwick, with close to 100% efficiency. Previously, heating was dependent on local diesel-generated electricity or oil-fired systems. The principal non-domestic users, who take around 60% of the heat produced and save considerable capital investment in boiler plants and associated maintenance costs, are: Anderson High School, Islesburgh Community Centre, Shetland Museum and Archives, Mareel, Holmsgarth Ferry Terminal, Gilbert Bain Hospital, Montfield Hospital, Clickimin Leisure Centre, which uses a special low-temperature heating circuit to heat its swimming pool to 30°C. The scheme supplies more private homes than public housing. While the Energy Recovery Plant is operated by Shetland Islands Council, the District Heating Scheme is run by Shetland Heat Energy and Power Ltd., a wholly-owned subsidiary of the Shetland Charitable Trust, which receives the Disturbance Receipts that were intended to compensate the people of Shetland for siting an oil terminal at Sullom Voe. In addition to the value of the capital works, and the jobs created, around £1 million annually remains in the Shetland economy through this initiative, rather than leaving the islands to pay for fuel-oil.
In its first year of operation, the District Heating Scheme was powered by solely by its backup boilers in the District Heating Boiler Station. This was because the commissioning of the Energy Recovery Plant was delayed due to a fire.
