Wood fuel goes to school in the UK
by N A Hall-Stride, CADDET UK National Team

A key aim of the UK's growing biomass industry is to demonstrate the viability of wood fuel as a provider of effective, environmentally-friendly heating for commercial and public buildings.

Weobley School. Photograph: Alastair Carew-Cox

Introduction

Theoretically, the UK market for wood fuel is extremely large: thousands of rural businesses, schools and other services have the potential to install wood-burning heating systems. Promoting wood fuel in the rural sector would be of benefit to both the environment (wood is a carbon-neutral fuel) and the economy (utilising a locally-produced resource would help stimulate local jobs, etc). However, before these benefits can be realised on a meaningful scale, awareness about wood's viability and availability needs to be raised. A demonstration project at Weobley School is proving that wood-fired heating is a credible option.

The background

Following the 1992 Earth Summit in Rio de Janeiro, development officers at Hereford and Worcester County Council decided to make a real contribution to local sustainable development and stimulate rural employment. Working with the Rural Development Commission (RDC) and the Ministry of Agriculture, Fisheries and Food (MAFF), it was agreed that a new primary school, due to be built at Weobley, would be a suitable demonstration project. It would incorporate a heating system fuelled by locally-grown wood, have high standards of energy efficiency, and use local building materials wherever feasible.

The project

The project involved installing a 350 kW wood-fired boiler to meet the primary school's baseload heating needs, as well as those of a secondary school on an adjoining site. An oil-fired system, situated in the secondary school, provides back-up if the wood-fired system is undergoing maintenance, or when heating demand is particularly low and use of the wood-fired system is not practical. It also provides top-up heat at times of peak demand. As well as meeting the need for heat, the system also plays an important educational role, helping the children to understand energy issues.

For any project of this scale, securing a reliable supply of wood fuel is essential. In the case of Weobley School, this was done by entering into a contract with the 7Y Machinery Ring in Leominster, eight miles away. This is a co-operative of more than 300 local farmers, labourers and agricultural contractors which meets the members' labour and machinery requirements, and has agreed to supply the school with 150­300 tonnes/year of wood chips. The chips are currently derived from woodland thinnings; willow and poplar short rotation forestry crops will also be used in the future. Once harvested, the wood is allowed to dry on-site before being chipped and transported to the school.

At the school, the chips are stored in a semi-basement, concrete silo built to receive the weekly deliveries. Pushrods in the silo move the chips to the screws that take them up to the stoker, which in turn moves them to the burner head for combustion. The hot gases produced pass through the boiler; the heated water from the boiler is then pumped to the school's underfloor heating system. Exhaust gases are cleaned prior to emission into the atmosphere through a low-level chimney. The small amount o f ash produced by combustion and by the exhaust gas cleaning process is collected in an ash bin for use as fertiliser on the school garden.

The heating system was supplied and installed by Nordist, based on equipment specifications defined by consultants from Energy for Sustainable Development. Council engineers undertook a lot of the design work, and LRZ Bioenergy Systems provided advice on fuel source and quality. Routine cleaning and maintenance is undertaken by the school's caretaker, with an annual maintenance inspection performed by Nordist. Due to its innovative and environmental dimensions, the Weobley project was awarded first prize in the UK Engineering Council's 1997 Built Environment Innovation competition.

Economics

The school itself was built from the council's normal budget; additional funding of 79,000 (where is the UK pound) for the heating system was received from European Regional Funding (administered by MAFF). Matching funding was received from the RDC, the Department of Trade and Industry under its New & Renewable Energy Programme, and the County Council itself.

Conclusion

Weobley School represents just the type of scheme that should, by setting an example, help develop the market for wood fuel in the UK. This aim is also being pursued in other ways, not least by the Biomass Heat Market Working Group. The Group includes equipment suppliers, consultants, and current and potential growers of energy crops, and was established by British Biogen, the UK bioenergy industry's trade association, in 1995. Its aim is to promote the installation of wood fuel heating schemes of all sizes, from small-scale domestic installations to large-scale industrial projects. Progress has already been made in bringing together fuel and equipment suppliers and in targeting rural heating consumers who could make use of wood fuel. Indeed, members of the Group played a key role in the Weobley School project.

For more information contact the CADDET UK National Team in Oxfordshire.

The CADDET Renewable Energy Newsletter is a quarterly magazine published by the CADDET Centre for Renewable Energy at ETSU, UK.

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