COPPICING WOODLANDS
Coppicing is the act of periodically cutting a small tree, so that it produces many shoots rather than one main trunk.
If any British broadleaved tree is cut back to its stump it will regrow; periodic cutting back of trees can therefore provide a sustainable yield of wood more or less indefinitely. This form of woodland management is known as coppicing, with trees which are to be cut known as the underwood. In British coppices the underwood, in an area known as a cant or coup, is typically cut every 5 to 20 years. Coupes in a coppice woodland are cut on a rotation system to provide wood every year. The stools, or stumps, from which the new coppice growth arises, can remain viable for many hundreds of years, outliving several times uncoppiced trees of the same species. Coppice can be worked either as "simple coppice" or "coppice with standards". Simple coppice consists entirely of trees to be coppiced - i.e. entirely of underwood. More common is "coppice with standards" where, in addition to the underwood, uncoppiced trees are allowed to grow to form an upper storey; these standard trees were usually used for specific purposes such as building houses, barns or boats.
HISTORY
The isolation of settlements and industries meant that timber had to be procured from the immediate area. This necessitated perpetual management of woodlands in order to produce a constant timber crop. Rotational cutting over an area of woodland gave a constant supply of wood which was used in every aspect of life.
By the mid 1800's the decline in rotational cutting had begun. More and more oak standards were planted to supply the rapidly expanding tanning and ship building industries - ironically both demands collapsed before the felling time but the inevitable shading weakened the coppice system. Other factors aiding the decline included, improved transportation, which carried the exploitation of coal for fuel, and brick and stone for building to rural settlements and industries. Since then two world wars have decimated the rural communities who managed these rotational systems, coupled with the march of modernisation in agricultural practices which have caused many ancient woodland sites to be grubbed up and changed to extensive softwood plantations, or to increase productive field sizes for crops or pasture land for grazing stock.
Today it is estimated that over 90% of remaining coppice is out of cycle or derelict, though even this state in conservation terms is far more favourable than plantation or field systems.
Coppicing has been shown to be of great value to wildlife and an important tool in maintaining diversity. Coppicing on a rotation provides a mosaic of graduations between light (immediately after cutting) and shade (after canopy closure, 4-10 years later); this and other environmental variations provide habitats for a wide range of plant and animal species. Rotational cutting creates a constantly recurring cycle and its important to remember that most of our native flora woodland species and wildlife have evolved under the coppice system.
The species most commonly coppiced include sweet chestnut, hazel, hornbeam, oak and ash. The coppiced wood can be used for a variety of purposes suited to the particular properties of the species.
THE VALUE OF COPPICE WOODLANDS
There are many different values which can be placed on coppice woodlands. These may be in economic, social, cultural and environmental terms and can be listed as follows:
- a renewable source of wood;
- a source of employment;
- amenity and recreational use - including orienteering and mountain-biking;
- wildlife and conservation value;
- landscape value;
- cover for game birds;
- heritage value;
- an example of sustainable land-use; and
- rotational coppice biomass/energy crop.
HOPEFUL SIGNS FOR COPPICE WOODLANDS
There are however some hopeful signs for coppicing as there is a renewed interest from conservation groups, as a sustainable form of woodland management. They are re-coppicing areas purely for their conservation and wildlife value.
In addition, there has been a revival of interest in traditional crafts and the area of worked hazel coppice has increased. Hampshire County Council has been supporting the hazel coppice industry and has pioneered a grant scheme to regenerate derelict hazel coppice through production of thatching spars and wattle for fencing and garden furniture.
More recently in Kent there have been proposals to establish one or more electricity generation plants fuelled by coppice wood, which would consume a considerable amount of the latter. This is possible due to the Government's continuation of the "Non-fossil Fuel Obligation", ensuring that electricity generating companies must generate a minimum percentage of their power from renewable sources in order to be allowed to supply the national grid.
Chestnut is still cut for fencing and hop poles, though at a reduced level, and some coppice is sold to pulp mills and particle-board factories.
The value of coppice as shelter for game birds has meant that a certain area has been managed primarily to create cover for pheasants. Shooting continues to be an important motivating factor for woodland management, with the creation of habitats for wildlife as a secondary output.
OTHER TRADITIONAL CRAFTS; such as hedgelaying, hurdling etc are seeing a large and sustained revival of interest coupled with the grant schemes and the governments commitment to AGENDA 21, which aims at integrating the needs of development and the environment by promoting sustainable consumerism and agriculture through the use of local materials. The public are very receptive to environmental issues and the market for sustainable locally made produce is growing daily.
THE ECONOMICS AND USES OF COPPICE MATERIALS
Short rotations such as hazel make favourable income compared to other broadleaved crops. In addition it will provide a livelihood for approximately 10 times as many people as a similar sized wood managed by modern forestry methods. Hazel is used between the years 6-12 any older and it fast becomes a liability to clear and restore to cycle. Prices paid by coppice workers for standing in-cycle hazel vary widely per acre depending on quality, but a well stocked acre of 8 year old hazel should produce 10,000-12,000 rods of 10 to 15 feet in length. This can be converted into approximately 300 x six foot square hurdles, or 75,000 thatching spars. In addition assorted bean and pea sticks, clothes line props and the occasional oak or ash standard. Other uses include stakes and ethers for hedgelaying, charcoal, pulpwood, wood chips, turnery, firewood, garden products, compost bins, tree guards, clothes pegs and tent pegs, walking sticks and rake handles. Other coppice species include Alder, Apple, Aspen, Birch, Sweet Chestnut, Lime, Hornbeam, Ash, Oak, Maples and Willows. All having a multitude of uses and income.
COPPICING TO GENERATE ELECTRICITY
Coppice woodlands can be considered a valuable resource for the future as they represent a renewable source of biomass produced in a way which is sensitive to the ecology of the region. In south-east England the potential for biomass production from traditional coppice is estimated to be 300,000 tonnes per annum. All of this coppiced Biomass could be converted into approximately 140 million watts of renewable electricity per year.
Burning coal, oil and gas inevitably produces carbon dioxide, a key greenhouse gas, as well as gasses related to acid rain. Nuclear power involves the generation and storage of highly dangerous and long lived substances with the added 'high' risk of major accidents.
By contrast growing and burning energy crops can be greenhouse gas neutral, as long as the regrowth rate balances the use rate, so that as much carbon dioxide is absorbed as is produced by combustion. Regularly coppiced plantations will actually absorb more carbon dioxide than mature trees - since Co2 absorbtion slows once a tree grows.
It is envisaged that large parts of the set aside land - representing 15% of UK arable land - might be used, which represents a sizable energy resource. The governments D.T.I. estimate that by 2025, Biomass short rotation arable coppicing could supply half of the UK's electricity requirements.
The biomass resource should be considered as the most efficient and promising renewable energy source for and from our rural sectors, the potential is enormous but it is fair to say that this resource should not be carried out in isolation of other renewable energy issues.
Charcoal production is one industry which can, given the introduction of appropriate technology, encourage the reworking of ancient coppice woodlands by creating a market for the coppice wood. The revival of coppicing and charcoal production will require that partnerships be formed - from woodland owners, technologists through to retailers of the charcoal.
COPPICING AND THE CHARCOAL INDUSTRY
One traditional use for coppiced wood was for charcoal production. The charcoal was used for smelting iron and in the manufacture of glass. Today the main markets for charcoal are for leisure use in the form of barbecues and commercial catering (e.g. Tandoori restaurants). The UK imports over 95% of the charcoal sold on its domestic market, with the bulk coming from tropical mangrove forest, an endangered habitat.
As a habitat, mangrove is under pressure on a global scale. The majority of the charcoal from south-east Asia as a whole is from mangrove forest.
The main pressure on mangroves in south-east Asia are their clearance for shrimp fisheries, with the wood cleared being converted to charcoal to generate additional revenue.
IMPORTS
The cheapest imports are from south-east Asia, with wholesale prices for the bulk charcoal under 200 per tonne. UK charcoal is around 300. The price structure reflects quality of charcoal - that is the "fixed carbon content". South-east Asian charcoal is dense and poorly carbonised with a fixed carbon sometimes as low as 65%. This makes it heavy and thus accounts for its cheap price on a weight basis. British charcoal is well carbonised and hence less dense and correspondingly more expensive on a weight for weight basis, but with a fixed carbon content of over 80%. Briquettes can contain up to 45% of volume in sand.
BRITISH CHARCOAL
Producers of British charcoal maintain that the prices for barbecue charcoal quoted on a weight basis will always give a misleading impression on the value for money of imported versus British charcoal. They maintain that British charcoal is of higher quality, lights more easily and reaches cooking temperature more quickly than imports; plus the barbecue user gets more burn for his/her money from the British product. Thus they claim that the British product offers genuine value for money. A 3kg bag of British charcoal has a greater volume than 5kg of the most dense south east Asian import.
PORTABLE KILNS
Charcoal produced using portable kilns is of a high quality with a fixed carbon content in excess of 80%. Conversion ratios of wood:charcoal are low, between 6:1 and 8:1. (Meaning six tonnes of wood will produce 1 tonne of charcoal).
Generally, portable ring kilns cannot be operated on an economically viable basis in the UK. All burners in the UK receive at least part of their income, or indeed the bulk of it, from other operations, in effect subsidising the production of charcoal. Even using primitive and inefficient technology such as the portable steel kilns, this system could still provide more than one and half times the charcoal requirement for the whole of the UK. What is desperately needed is small, efficient technology with low emissions, that are mobile or portable, with an organisation structure that enables the charcoal to be processed, marketed and distributed effectively.