Warmth from waste

For more than twenty years, Shetland’s waste to energy system has used the islands’ combustible rubbish – supplemented by Orkney’s – to heat homes, businesses and public buildings in Lerwick.

At a time when all of us must try to reduce our carbon footprint, it significantly reduces the demand for heat generated from fossil fuel sources. It also reduces, dramatically, the need for waste to go to landfill, and there are other benefits.

The scheme was conceived in the early 1990s. The Shetland Islands Council had, for many years, operated an incinerator that simply burned rubbish, but it was faced with new environmental regulations with which the existing plant couldn’t comply.

The Shetland Charitable Trust was keen to make investments that benefitted the community and involved innovation. After studying examples of successful waste to energy schemes elsewhere, particularly in Denmark, both organisations gave the go-ahead for the main elements of the project in 1997, and the first customer was connected in November 1998.

The Council’s contribution involved the building of a new incinerator that could heat large volumes of water to serve the needs of what was to become a district heating network. The new Energy Recovery Plant (ERP) overcame the environmental shortcomings of the old incinerator and enabled waste that couldn’t be recycled to be transformed into useful heat.

The ERP generates 7MW of energy, burning around 23,000 tonnes of waste per year. An overhead crane drops about 3 tonnes of waste into the furnace every hour, where the temperature is around 1,200°C. The hot water boiler, attached to the furnace, has a capacity of 50 tonnes and it heats water to 115°C. The temperature is lowered before the water is sent out to users around the town.

Meanwhile, a specially-formed company – Shetland Heat Energy and Power (or SHEAP, as it’s usually known) – began work on the underground web of insulated, underground pipes that would carry the hot water around the town.

SHEAP also constructed a Peak Load Boiler Station, the exterior of which is shown in the image at the top of this article. It pumps the water around the network and also provides a large hot water store. Back-up boilers can be used when demand for heat is particularly high or when the energy recovery plant is undergoing maintenance.

Expansion of the network proceeded steadily; by 2002, the part of Lerwick farthest from the Peak Load Boiler Station – the Sound area – had a connection. In 2006, a ring main around the town was completed when the newly-constructed Shetland Museum and Archives came online. The 1,000th domestic customer was connected in 2011. More than 30km of pipes now carry the heat to all these premises.

Over recent years, more buildings have come to rely on the scheme, including – in 2017 – the new Anderson High School and its halls of residence. There have been many improvements to the system since it was first established. For example – long before electricity companies began installing “smart meters” – SHEAP had introduced a radio system that could transmit customers’ meter readings whenever required. Further expansion is possible, but would require additional heat sources or modifications to the Energy Recovery Plant.

The excellence of the project was recognised in 2000, when it won the Environment Award for Engineers. In 2008, the Scottish Environment Protection Agency was so impressed with the scheme that it launched a DVD aimed at encouraging other local authorities to adopt a similar solution.

SHEAP’s Annette Stickle draws my attention to the Shetland Heat Energy and Power Facebook page, on which you can watch the video contained on that DVD. Although it was produced a few years ago and some details have changed, it describes the process very well.

Staff at the company have often been involved in introducing the scheme to interested visitors.

It’s clear that the district heating scheme has many advantages for users. Installation is straightforward: a heat exchanger is fitted in the home that enables heat to be transferred from the hot water main into the separate domestic pipework. Customers can enjoy instantaneous central heating, whenever they need it, rather than having to guess how much heat they’re likely to need from electric storage heaters a day or so ahead. They also benefit from an unlimited supply of hot water.

Compared with solid fuel or oil systems, there’s no smell, noise, dust or ash. What’s more, it’s a local company, so users can speak with a friendly voice at the end of the phone, rather than navigate the menus and music-on-hold of some distant call centre.

The price of the heat is highly competitive. As the graph below shows, it compares very favourably with that from electric storage heaters and – except at times when oil prices are particularly low – with oil.

The environmental merits are compelling. It’s not simply that the heat is generated from waste rather than fossil fuels. There’s another less obvious but very substantial benefit. Much of the waste that reaches the incinerator is of a biological nature – food waste and the like. Were that simply to be dumped in landfill, it would generate significant amounts of methane, which, as a greenhouse gas, is around twenty times more potent than carbon dioxide. The plant also burns a small amount of waste oil derived from drilling mud.

There are other gains, too. The Charitable Trust’s investment is rewarded through the return of SHEAP’s profits to its reserves, strengthening its ability to assist a wide range of charitable activities in the islands, particularly through its support for the three large trusts that focus on arts, heritage and recreation.

The cost of providing independent boilers to serve large buildings such as the Anderson High School has been avoided. The scheme overall has created about 30 jobs and local plumbing and civil engineering firms have gained business; about £1m of income flows into the islands’ economy rather than leaving Shetland. The landfill tax liability has been reduced.

It’s clear that the staff to whom I spoke during a recent visit are very enthusiastic about the district heating scheme. Manager Derek Leask points to the system’s environmental merits and stresses, too, the role that they play in helping to tackle the issue of fuel poverty. He adds that legislation now passing through the Scottish Parliament will encourage more use of heat networks of this kind.

Lucy loves the scenery and the ability to enjoy it so easily. She’s a keen walker and hiker who’s spent many days exploring the Peak District and the Lake District, so Shetland’s wild places really appeal to her, and she used to bring her tent and go wild camping.

“It’s really varied scenery, too. You can get to Eshaness and see those volcanic cliffs; in the South Mainland you have sandy beaches. You can go to Foula, and you’ve got this amazing ridge walk. I just think it’s never-ending. And there’s the wildlife! I’ve seen killer whales when I’ve been here and there are all the birds, too: everyone loves puffins.”

“Then there are the people. I knew when I got here that everyone would be very friendly and welcoming, and they really have been. I feel very settled, even though I’ve only been here for three months. I’ve made friends with people that I was with at primary school and they’ve really supported and helped me in moving here. So yes, scenery, wildlife, people, culture!”

Lucy has even set herself a target of visiting all 77 of the Ordnance Survey trig points this year – she’s already managed seven of them. Another aim is to become a walk leader.

It’s easy to understand why the staff are so enthusiastic. All in all, the waste to energy plant and the district heating scheme have proved to be far-sighted and innovative investments. The project as a whole has helped reduce the islands’ carbon footprint and it has also brought social and economic advantages.

Let’s hope that it continues to flourish and offer an example of best practice to communities elsewhere.