Blaise-Biomass Case Study

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BIOMASS CASE STUDY

BLAISE NURSERY, BRISTOL

Bristol City Council

INTRODUCTION

Bristol City Council's plant nursery in the grounds of Blaise Castle estate produces over 1.5 million plants per year for thecity. It also grows, supplies and delivers plants for many other authorities. It supplies 5,000 hanging baskets and troughsand can also organise, supply and maintain indoor decorations and house plants. 70% of the plants are grown in peat-

free soil in poly-tunnels and glass houses that cover a total area of more than 8,000m².

In 2001, Energy For Sustainable Development (ESD) carried out a broad survey of several Bristol sites including Blaisefor possible development of sustainable energy faci lities. In 2003, The Centre for Sustainable Energy (CSE) carried out afeasibility study to investigate the possibilities for specific biomass projects within the city council's sites. The studyidentified Blaise Nursery as a potential site for a biomass boiler to heat its poly-tunnels and glass houses, using locallysourced material in the form of wood chips from the city's parks, estates and other maintenance activities.

In October 2006 a new 400kW biomass boiler was installed and commissioned.

BUILDINGS

The nursery's activities are spread across eight poly-tunnels and glass houses of varying sizes – the smallest is 129m²and the largest 2,400m². Until now these have been heated during the growing months of March to May by a

combination of heating systems using oil and LPG. The photograph below shows part of the site.

To heat these during the growing months, the council was spending about £19,000 a year on oil and LPG, and it was

estimated that it was producing over 100 tonnes of CO² per year. Meanwhile the council was also producing biomassresidues of 2,000 – 3,000 tonnes a year from its arboricultural activities. A small percentage was being sold whilst therest was being spread around woodlands.

PROJECT DEVELOPMENT

CSE carried out a feasibility study in 2003 to consider the opportunities for a biomass boiler but this showed that theeconomics were marginal. In the early stages of the project Dr Robin Cotton of Wood Energy Ltd provided much adviceand general information to Bristol City Council employees about biomass systems as this was a new subject andexperience in the UK was limited. Wood Energy then carried out a more detailed feasibility study. It was decided that in



spite of the marginal economics of the scheme, it would go ahead, as the project would act as a flagship and focal pointfor others to follow. MCA Consulting Engineers based in Sussex produced a full design and provided projectmanagement services.

It was also decided to create a wood reclamation centre on the site, where the arboricultural materials could be chippedand stored. The storage area was designed to be larger than necessary for the nursery's needs so that the chippedmaterials could be used not only to feed the boiler at Blaise but also used in other council biomass locations.

HEATING SYSTEM

The boiler selected for the site was a step-grate Binder RRK 400 – 600 wood chip boiler from Austria, supplied by WoodEnergy. The boiler with its controls and accumulator tank of 10,000 litres cost approximately £80,000. After allowing for aBio-energy Capital Grant of 25% the net cost was approximately £60,000. There was an existing nursery building usedfor storing agricultural machinery that had sufficient space to house the new boiler, but since the site is large and spreadout, underground mains piping with six branches needed to be laid with a total length of approximately 200 metres,connecting the poly-tunnels and glass-houses to the boiler system. Insulated piping from another Austrian manufacturer,Flexalen, was selected for this. The costs of the pipework and associated work amounted to over £100,000.

The photographs below shows the main boiler house with the wood store alongside, and some of the poly-tunnels withthe two of the air heating system fans suspended from above.

FUEL SUPPLY AND STORAGE

In order to develop the wood reclamation centre, a new building was erected to store the finished chips alongside theboiler house and a concrete area was created beside the building for chipping and screening machinery to be deployed.The council's contractor brings all the arboricultural materials, both wood chips and core wood to the site. The core woodis stored and periodically the councils hires equipment to carry out its own chipping. Wood chip is then fed through a newscreening machine that eliminates unsuitable materials and feeds the finished chips into the covered wood store. In acorner of the wood store is the bunker that holds approximately 75m³ of chips from which a spring-loaded rotary arm andauger feed the chips to the boiler in the adjacent building.

A certain amount of drying occurs once the chips are in the covered store. The target maximum moisture content of thechips is 50%. The nursery is expected to consume about 300 tonnes of wood chip in the three months of the year when itis operating fully. The site supplies two other city council biomass installations at present – Florence Brown CommunitySchool and Netham Park Recreation Ground Pavilion which also have Binder wood chip boilers. Experimental work iscontinuing with the materials; shredding of pallets has been tried and temporarily suspended following problems withscreening out of nails but it is hoped eventually to generate enough biomass to supply other biomass installations acrossthe region.

During the first year of operation, the old LPG and oil burners have been retained as backup sources of heat. It is hopedeventually to replace them with a modern oil-fired boiler to act as backup in the event of breakdown.

The photograph below shows the fuel store and the screening equipment.



COSTS AND GRANTS

The initial feasibility study qualified for a £2,000 grant under the former SWEB scheme that is now called the EDF GreenEnergy fund.

The estimated costs for the total project were around £170,000, offset by the Bio-energy Capital grant of £20,000. Theestimates proved to be low, principally due to the costs of the extensive pipework, and the eventual costs totalled morethan £200,000. There were also additional costs for the new concrete hard standing area (£40,000) and the screeningequipment (£45,000). The boiler has an expected li fe span of 20-30 years.

The council is forecasting a payback for the investment of 9 years. This is based on expected annual fuel savings of£19,000 per year in oil and LPG but does not include all of the capital costs incurred such as new concrete standing andscreening equipment. It also ignores the cost of chipping and processing the arboricultural residues since it is hoped togain additional revenues from sale of biomass materials.

LESSONS LEARNED

It was hoped initially that the chips from arboricultural arisings would be sufficient to fuel the step-grate boiler withoutfurther processing, but this proved to be difficult and there have been issues with the quality of the fuel. The installation ofnew screening equipment is expected to resolve the problems.

Bristol City Council staff believe that they should have tried to get firm quotations from suppliers before applying forgrants since the quotations and actual costs of some aspects of the project proved to be wide apart. They feel that theyshould also have been more meticulous in checking project plans and costs. The project proved to be a challenginglearning process and several staff would have l iked a longer period of “hand-holding” from the suppliers, but hope that byhaving completed the facility and hosting visits from other interested people, the renewable energy community at largewill gain significant benefits on the back of their experience.

Summary facts

Boiler manufacturer Binder

Model RRK 400-600kW

Size 400kW average; 600kW peak

Fuel type Wood chips

Supplied by Wood Energy Ltd

Buildings served Poly-tunnels and glass houses

Service provided Air heating

Maximum moisturecontent

50%

Maximum particle size 85mm

Wood fuel storagevolume

75m³

Cost of boiler, controlsand buffer tank

£80,000 approx



Grant obtained £20,000 approx

Date of commissioning Oct 2006

Name of owner Bristol City Council

Address Blaise NurseryKings Weston Road, Bristol BS10 7QS

Contact Paul Barker, Environmental Management Officer(0117 922 4438)

Contacts

Wood Energy Ltd Wood Energy LtdPinkworthy Barn,Oakford,Tiverton,DevonEX16 9EU

Tel: +44 (0) 845 070 7338Website: www.woodenergyltd.co.uk

MCA ConsultingEngineers

MCA Consulting Engineers Ltd17/18 Newhouse Business CentreOld Crawley RoadFaygateWest SussexRH12 4RUTel: 01293 851490

Website: www.mcaltd.co.ukFlexalen Energy Ltd Flexalen Energy

Unit 1Station Road Ind. EstateStation RoadMethil, FifeScotlandKY8 3HA

Tel: 0845 644 3793Website: www.flexalen.co.uk

ACKNOWLEDGEMENTS

This case study has been produced as part of the Knowledge Exploitation South West project (KESW2) funded by theSouth West Regional Development Agency.

OTHER USEFUL CONTACTS

Biomass Energy Centre

The centre is run by the Forestry Commission and draws together information from existing sources into one easy-to-usewebsite and an information enquiry service.

Biomass Energy CentreAlice Holt LodgeFarnhamSurreyGU10 4LHTel: 01420 526197

Website: www.biomassenergycentre.org.uk

South West Woodshed

This website lists all future woodfuel training and other events in the South West and provides a facility for bookingplaces on courses. It is run by Regen SW and is funded by the South West RDA.

Website: www.southwestwoodshed.co.uk Woodland Renaissance

The South West Woodland Renaissance Partnership vision is to regenerate woodland and forestry in the South West for



the benefit of the economy, society and the environment.

Website: www.silvanus.org.uk/woodland_renaissance.php

Woodfuel South West Advice Service

The service is funded by the South West Woodland Renaissance Partnership and is a source of advice for anyone

considering installing automated wood chip or wood pellet heating. It operates within the Centre for Sustainable Energyorganisation.

Tel: 08450 740674

Nov 2007

Blaise-Biomass Case Study

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