Wood for energy

Sorting logs brought in by tree surgeons at the Croydon Tree Station

Wood is an age old fuel which fell out of use in Britain with the industrial revolution and advent of cheap fossil fuels. However, wood is still the primary fuel for people in many countries around the world, both developing and developed. In Britain, with increasing concern about climate change, wood is now an increasingly attractive energy source along with other forms of biomass. Modern biomass boilers are efficient and clean and wood energy is renewable, as once trees or other biomass such as elephant grass (miscanthus) are harvested they are replanted and grow again, reabsorbing the CO2 emitted when the wood is used.

Certification of good woodland management, supported by independent inspection, is the best guarantee of sustainably produced wood. Using wood for fuel will help bring under-managed woods back into management. This in turn will open up the woodland canopy allowing more light to reach the ground. Conditions will be greatly improved for wild plants, butterflies and animals which have been declining in recent years such as the dormouse and the nightingale.

In the UK there is a lot of timber potentially available for fuel. For example, in south-east England the National Inventory of Woodlands and Trees completed in 2000, indicated that over 1 million tonnes of fuel wood could be harvested each year. The Forestry Commission has a target of an additional 2 million tones of wood fuel produced from Britain’s woodlands annually.

If you are looking for supplies of wood fuel try the LogPile Project website. This allows you to search for local wood fuel producers anywhere in the country and has more background information about wood fuel. Government grants are available for installation of biomass appliances through the Low Carbon Buildings Programme.

Other sources of wood fuel

Woodlands are not the only source of wood fuel. In urban areas the trees on the streets and in parks and gardens all produce timber. A 2005 survey by BioRegional working with the London Tree Officers’ Association estimated that 127,000m3 of tree waste is produced each year. Much of this poses a disposal problem for tree surgeons.

Untreated reclaimed timber from demolition sites and clean waste pallets can also be used as fuel. Waste from timber using industries is increasingly used for pellet production. Finally, trees such as willow and poplar can be planted as short rotation coppice and cut every 2 or 3 years for fuel. An assessment was made by BioRegional of the wood fuel potentially available in London in 2005, identifying a minimum of 500,000 tonnes a year after allowing for existing uses. The report, Biomass fuel assessment for the Z-squared combined heat and power plant, is available for download from our publications page.

Wood and other biomass has an advantage over other renewables such as wind and wave since it can be easily stored until it is needed. This flexibility in use comes at a cost as it has to be harvested, processed and physically transported from where it grows to where it is used, slightly offsetting the CO2 emission reduction from using wood fuel.

Wood is now recognised as good value, at least as cost effective as other renewables. Following price rises for fossil fuels in 2005 wood chip is cheaper than natural gas. Its potential was recognised by the government when they set up the Biomass Task Force. Their report identified potential for wood fuels to save 3.6 million tonnes of carbon emissions nationally from existing resources. Planting biomass is an attractive way for farmers to diversify their businesses. The government’s response to the task force report, published in April 2006, supported its conclusions and contained commitments to foster the development of wood and other biomass as modern energy sources.

BioRegional and wood for energy

BioRegional has promoted wood for energy since 2001. Our aims are to:
• develop a commercially viable model for wood chip fuel supply at local scale;
• promote wood as a fuel and develop a supply chain for wood fuel across London and elsewhere; and
• work with others in the emerging industry to make using woodchip “as easy as paying the gas bill”.

Types of wood fuel
There are 3 main types of wood fuel used in modern systems in the UK, Europe and elsewhere

Logs
The traditional form of wood fuel which can be easily stored, air dried and burnt in a wide range of appliances from open fires to modern automated boilers.
The advantages of logs are:
• they are readily available, although there are no guarantees of quality so the buyer has to make sure they are suitable for the proposed use.
• bought in bulk, they are the cheapest form of wood fuel;
• they are almost always locally produced, so buying logs benefits local woodlands and the local economy.
The disadvantages of using logs are:
• there is no agreed quality standard, so logs may be the wrong size or too wet
• using logs requires more involvement than other forms of wood fuel, stoves have to be loaded and cleaned, and even highly efficient modern boilers have to be loaded on a daily basis.

Wood Chip
Wood chip is widely use in other European countries as a fuel for heating and in combined heat and power systems, particularly in countries with a strong forestry tradition such as Scandinavia and Austria. Wood chip boilers are available for all scales of operation though CHP plants are normally larger serving a town via a district heating scheme.
The advantages of wood chip are:
• it is cheap, often as cheap as logs and now (June 2006) cheaper than mains gas;
• it is a standardised product with Europe wide quality standards in place;
• fully automated, highly efficient boiler systems are available;
• it can be made from a wide range of raw materials, often sourced locally.
Its drawbacks are:
• fuel quality is often variable, since suppliers are still inexperienced;
• it can be difficult to find supplies without assistance;
• it is a bulky fuel, leading to storage problems in some sites, particularly at the domestic scale.

Wood Pellets
Wood pellets are a highly compressed standardised product made from sawdust, normally without other additives.
Their advantages are:
• they are a consistent fuel with low moisture content which can be easily handled in automated systems;
• a wide range of appliances are available to burn pellets, from single room stoves to large district heating systems. Fully automated boilers are the norm;
• bulk density is around 4 times that of wood chip, requiring less storage room making them more convenient at a domestic scale. In other countries bags of pellets are commonly sold on filling station forecourts.
Their disadvantages are:
• supplies of locally made wood pellets are hard to find in the UK, most are imported at present;
• they take energy to make and are often transported long distances, reducing the environmental benefits of using a wood fuel;
• they are expensive, around twice the price of wood chip.

BioRegional’s associated company BioRegional Forestry can supply logs in South London and nearby areas. BioRegional has set up a wood chip production unit in partnership with the London Borough of Croydon and City Suburban Tree Surgeons Ltd. For more information about wood chip supplies please contact Andrew Tolfts.

Pete Kavanagh of City Suburban Tree Surgeons at the Croydon TreeStation.

Developing local wood chip supplies

Wood chip fuel is increasingly seen as an important element in reducing our CO2 emissions. Wood provides the greatest amount of renewable energy across Europe, though this is over looked as most is used in small heating projects. The UK has very low levels of wood fuel use by European standards but is beginning to increase this as the economic and environmental benefits become clearer. There are clear commitments to support the sector from government and cost savings for users.

London is in the vanguard of biomass uptake thanks to policy initiatives by the Mayor and GLA. There is a city wide requirement for larger new developments to include 10% on-site renewable energy generation, with some boroughs having more demanding policies. Heating with wood is often the most cost effective way of achieving this and the use of wood chip and pellets is set to increase. Wood waste from tree management and commercial sources is generated all over London creating a substantial local fuel source.

BioRegional have been developing wood fuel in London since 2001, first for the BedZED project and latterly as part of the proposed Z-squared development. BioRegional’s TreeStation at Croydon is the first of its kind in the capital, processing tree surgery arisings into high quality graded wood chip fuel suitable for use in a wide range of boilers. With our partners we have demonstrated a commercially viable system for wood chip production at a local scale and provided a local fuel source to give developers the confidence to install wood chip heating systems. The work was supported by the Norlands Foundation, The Carbon Trust and Scottish Power’s Green Energy Trust.

All partners in the TreeStation benefit

• The council has a sustainable disposal route for arboricultural arisings which is £20,000pa cheaper than alternatives such as landfill; provides a disposal point for local tree surgeons; and has a local supply of wood chip, supporting its renewable energy policy.
• City Suburban Tree Surgeons are able to offer a more complete service to their clients by including the use of all waste as fuel and gains a diversification of their business; and
• BioRegional has practical experience of wood chip fuel production which we are able to use in promoting its uptake as fuel and developing the wood chip supply chain in London and elsewhere. The TreeStation at Croydon is used as a demonstration unit for others interested in wood chip production.

Full operation at the Croydon TreeStation was achieved in March 2006 with the site currently making around 70 tonnes of chip a week. This will rise to around 200 tonnes a week (around 8000t/year) by the end of 2006. All grades of chip commonly used in boilers can be made, depending on the users’ specification. Now most chip is sold green at around 45% moisture content but it can be supplied at 30% mc, improving its value as fuel. 8,000 tonnes of woodchip used in boilers each year replacing natural gas saves around 5,050 tonnes of CO2 emissions.

A case study report of development of wood chip production at Croydon will be available from July 2006 for download from our publications page.

Croydon Council is one of the leading councils in London in promoting renewable energy. Their policy requires that 10% of carbon emissions from new large developments are avoided by on-site renewable energy generation. This together with a local supply of woodchip has stimulated the uptake of biomass heating in the borough. More than 6 projects are in planning or implementation over the last year representing over 2MW of boiler capacity. This will need around 1,500 tonnes of chip annually. Other boroughs are adopting similar policies, enhancing the prospects for growth in biomass use across London.

The work at the Croydon TreeStation to develop the supply of wood chip fuel was recognised recently when we won a 2006 Ashden Award for Renewable Energy. We shall use the £15,000 prize money to kickstart the next phase of our work with wood fuel.

Croydon is an example of an urban TreeStation. For more information about TreeStations in general follow this link: TreeStations

Filling a trailer with C50 grade chip for use in larger boilers

Future work with biomass fuel

The Croydon TreeStation is a one step towards establishing a capital wide biomass supply chain. We intend to build on our experience at Croydon and set up additional wood chip production units around London, working with local authorities and commercial partners. We shall also look at other sources of wood chip such as packaging and commercial waste and recycled timber. Our aim is to ensure that as the demand for wood chip fuel grows there is a local supply to meet it and that it is as easy and convenient to use wood chip as paying the gas bill.

Outside London we anticipate working with planners and developers to create local supplies of wood chip for use in new building projects and older properties converted to biomass heating. This will include energy crops such as short rotation willow coppice, thinning and coppice produce from existing woodlands brought back into management in addition to the waste timber we have been using in London. We are able to assist in the planning and establishment of local supply chains.

Contacts
For more information about wood chip production, supply and use please contact Andrew Tolfts, Forestry Manager, t: 020 8484 4891, email: Andrew Tolfts

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Last updated 14th January 2008