Upgrades to Lerwick Energy Recovery Plant

Continue and, where possible, accelerate current energy efficiency, energy conversion, waste reduction and reuse initiatives, within the council and across the community

Shetland Islands Council’s Energy Recovery Plant burns waste which heats water in a boiler. The hot water is supplied to a company, SHEAP, who distribute and supply the hot water to the public through a network of pipes, the Lerwick District Heating System.

The original refractory combustion chamber (brick built structure) was at end-of-life and needed to be completely replaced in summer 2021. Significant issues had been identified where brickwork had shifted and large cracks were discovered for the first time – this necessitated a full rebuild as soon as practicably possible.  Remedial work allowed operation of the plant to continue in the interim but a full rebuild and upgrade (with newer technology) was required to optimise combustion within the chamber.

In the 2021 Our Ambition progress report, the council noted how it had installed essential upgrades to the Lerwick Energy Recovery Plant, which would lead to improved efficiency and capacity, as well as a reduction in carbon emissions. 

The project focused on the water cooling systems and included a new water-fed heat exchanger being installed within the furnace to replace the existing concrete and brick refractory walls.

This project suffered commissioning difficulties as we did not fully anticipate that eliminating a build-up of slag in the refractory combustion chamber would see the problem transferred to other parts of the system down the line. Solutions and remedies have had to be found and put in place to minimise this, and this took time which pushed back the full potential of the plant.

The issue was compounded by the fact that, while the plant was shut down, we temporarily stored waste in the landfill with the intention of incinerating it when the plant was put back in service. Unfortunately, project delays moved the project into a period when we experienced a particularly wet period of weather, which soaked the waste and meant it had a much lower calorific value when recovered. In turn, this damp waste performed poorly in the furnace and generated much less heat than it should have at precisely the wrong time of year. Leaving it in the landfill wasn’t an option, as we would have become liable for significant landfill tax had we done so.

Lessons have been learnt and these upgrades should mean less frequent and lengthy shutdowns, while also bringing an ageing piece of infrastructure back to the forefront of energy-from-waste technology.