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Will biomass-powered district heating work in the UK?

Sustainability editor Hattie Hartman considers the potential for locally sourced heating systems

Imagine that every village in areas where timber is plentiful – in Scotland, say, or in the South East – had its own biomass-powered district heating system. Local farmers would deliver lorry loads of wood chip to a central plant, which would supply the community’s heating and sell electricity to the grid. I visited such a facility near Gresten, Austria, a village of 2,000 people, two hours west of Vienna. Is this kind of plant possible in the UK?

Austria’s energy equation – 80 per cent of its gas and 90 per cent of its oil is imported – is significantly different from that of the UK, as is its plentiful forest cover: 43 per cent, compared with about 9 per cent here. This has stimulated investment in sustainable power. Over the past two decades, Austrian govern­ment subsidies, both at federal and provincial levels, have resulted in a thriving renewables industry using both biomass and solar technologies.

HEAT AND EFFICIENCY - HOW BIOMASS FUEL TYPES COMPARE
 Wood pelletsWoodchipWillow
Calorific value17/0GJ/t13.4GJ/t19.7GJ/t
- per kg4.7kWh/KG3.7kWh/kg5.5kWh/kG
- per m33,077kWh/m3750kWh/m32,310k/Wh/m3
Moisture content8 per cent25 per cent25 per cent
Density650kg/m3200kg/m3420kg/m3
Ash content (per cent of mass)0.5 per cent1 per cent1.2 per cent

In the UK, various grant programmes, such as the Low Carbon Buildings Programme, have stimulated the biomass market. The Renewable Heat Incentive, being developed by the Department for Business, Enterprise and Regulatory Reform (Berr) is likely to promote biomass further. New technical guidance includes the Carbon Trust’s Biomass Heating: a Guide for Potential Users, released in February, and three guides developed by the RIBA and the Chartered Institution of Building Services Engineers, which are yet to be published. Of particular interest to architects will be one on how to conduct a feasibility study for biomass.

Biomass is the best way of ensuring 10 per cent of UK electricity comes from renewable sources by 2010

In 2004, there were only 11 biomass generating stations in England and two in Scotland, according to the government’s Biomass Task Force Report, published in 2005. In 2008, England had 448 and Scotland 173.

Rob Cooke, of engineering consultancy Buro Happold, notes that biomass is the easiest way of meeting the government’s requirement that 10 per cent of the UK’s electricity comes from renewable sources by 2010.

He says: ‘Savings of up to 50 per cent can be achieved. Biomass will not be so different to old-fashioned coal deliveries, once the market has matured.’

Arup’s Chris Twinn estimates that between 10 and 15 per cent of UK energy needs could be met by biomass without compromising food production. Britain’s woodland is under-exploited, as is the timber content in the waste stream. Specialists concur that biomass installations are only viable where fuel can be sourced locally – preferably within a 30-mile radius.

Biomass is particularly well-suited to small to medium-scale local heating in the 50 to 500Kw range near a stable fuel source. Most of the kit on the market is imported from Austria and requires a plant room and a fuel store, which is often built under­ground in order to facilitate deliveries of fuel.

Biomass boiler distributor Econergy has supplied boilers to more than 50 schools, most recently a 320kW wood chip boiler by Austrian manufacturer Froling to St Mary Magdalene Academy in Islington, London (2008), designed by Feilden Clegg Bradley Studios. Even Stansted Airport’s extension, completed last year by Grimshaw, has one. BAA announced last month that its 2MW boiler, supplied by Austrian manufac­turer Gilles, reduced gas consumption at the airport by 30 per cent compared with the previous winter.

DESIGN CONSIDERATIONS

• Availability of a local source of suitable fuel
• Size and location of fuel store
• Mechanism for transferring fuel from store to boiler
• Access for lorry deliveries
• Headroom for lorry tipping
• Delivery frequency
• Plant room size larger than conventional boiler
• Flue size and ventilation requirements
• Need for back-up system
• Increased capital cost
• Ash storage and removal
• Maintenance regime

But concern has surfaced about air pollution produced by biomass. The City of Edinburgh Council has halted biomass boiler installations in the city while the Scottish government studies the issue; and the Renewable Energy Association has a London Pollution Study Group. Fitting air pollution abatement technology to boilers is thought likely to resolve this issue.

Damian Markham-Smith, of engineering consultancy Gifford, worked on biomass installations in Bristol in the first round of the Building Schools for the Future programme. He estimates that a biomass plant costs £400-500 per kilowatt of capacity to install. Geothermal technology can cost three times that amount.

Andrew Mellor, of PRP Architects, notes a recent backtracking on biomass installations, particularly in urban locations, as clients focus on overall carbon reduction rather than just meeting renewables requirements.

Architecture practice Penoyre & Prasad sees district-scale energy transfer networks as the next logical step for biomass in the UK. Its Crouch Hill Community Park, currently in for planning, proposes to export energy off-site to nearby housing. A handful of district schemes are already operating, but Austria shows that much more is possible.

www.biomassenergycentre.org.uk

www.carbontrust.co.uk

Readers' comments (2)

  • I am looking to source a wood chip boiler (I think) Idealy one that could burn pallets.

    Any advise would be welcome

    to heat a 4 story mill with barn approx 4,500 sq ft

    Unsuitable or offensive?

  • Will Frost

    Stephen I assume you are looking for a boiler that will burn chipped pallets in which case there are many options available in the plus 250kW scale. Boiler will need to be able to take G50 grade wood chip, rather than G30 wood chip. You will find most pallet wood is actually shredded rather than chipped.

    Unsuitable or offensive?

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