The environmental impacts of arable coppice power generation — A case study from Cornwall, UK

The environmental impacts of arable coppice power generation — A case study from Cornwall, UK

Renewable Energy, Vol.5, Pint I1, pp. 741-749, 1994 = = sass=°e~ol B El~vier Science Ltd Printed in Gre~ B~'lain 0960-1481/94 $7.00-t0.00 THE ENVIRO...

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Renewable Energy, Vol.5, Pint I1, pp. 741-749, 1994 = = sass=°e~ol B

El~vier Science Ltd Printed in Gre~ B~'lain 0960-1481/94 $7.00-t0.00


ABSTRACT This paper is concerned with the assessment of the environmental impacts associated with a 2.SMW biopower station, fuelled by arable coppice, to be developed at a rural site in Cornwall, South West England. The project represents a new form of energy production for the UK and the first one of its type to be subject to environmental assessment in this country. The study was carried out on behalf of South Western Power Ltd and in support of its application for planning consent to build and operate the facility. The environmental assessment (EA) was comprehensive and reviewed the possible impacts of the plant on air and water quality; noise; landscape; socio economics, ecology and cultural heritage. Impacts during the construction phase were also considered. The study concluded that, with the exception of visual amenity, the plant would have no significant environmental impacts. Mitigation measures to reduce visual impacts in the form of landscaping around the site were introduced to reduce visual intrusion. Positive benefits would be derived through employment potential and through reductions in greenhouse gases and other polluting emissions. The development of this type of renewable energy plant would represent a significant step towards establishing a new type of environmental benign energy production method in the UK. INTRODUCTION South Western Power Limited (SWP) is a wholly owned subsidiary of South Western Electricity plc (SWEB) and owns a portfolio of power generation plant located mainly in South West England. SWP currently owns 12 power stations, including three windfarms. The Company has an active renewable energy programme As part of SWP's renewable programme, the company has been investigating the potential for wood as a source of fuel for some time. There are large areas of agricultural land in Britain that have been taken out of production under the EC's Set-Aside Scheme. This scheme takes agricultural land out of production in Member States to avoid surplus production of agricultural produce. Grants are paid to farmers who participate in the scheme. It is estimated that some 1 - 1.5 million hectares of land will be taken out of production through Set-Aside by the year 2 0 0 0 . 741

742 Arable coppicing involves the planting of unrooted cuttings of Willow and Poplar at high densities of 10,000 trees per hectare with the harvesting of coppice on a short rotation cycle of 3-5 years. If set aside land were to be made available for the growing of wood for coppicing, it has the potential to provide approximately 10 million tonnes of coal equivalent per year. PLANNING CONSIDERATIONS Development of renewable energy projects in the UK requires planning consent from the local planning authority in whose area the project is to be developed. It is only recently that planning policy guidance on renewable energy has been articulated by the Government in the form of a Planning Policy Guidance Note - PPG22 [1]. This document establishes the principles which should be taken into account by both developers and local authorities when considering renewable energy projects. Central to these principles is the requirement to undertake an environmental assessment of the project prior to granting consent. This assessment should be carried out in accordance with the regulations [2] which implement the requirements of European Community Directive 85/337/EEC concerning the assessment of the effects on the environment of certain public and private projects. An environmental assessment of the proposed Cornwall Biomass Power Plant was therefore undertaken as part of the planning consent procedures and an environmental statement (ES) documenting the anticipated environmental impacts was produced. This paper summarises the key issues identified during the environmental assessment of the proposed plant - the first arable coppice fuelled power station to be developed in the UK. THE PROJECT The project involves essentially the conversion of coppice wood chips into electrical energy. This involves combustion of the wood fuel in a purpose designed furnace, the raising of steam in a boiler and the subsequent generation of electricity via a steam turbo generator. Wood chips will be brought to the power station site from the coppice growing areas in lorries each day. After temporary storage in a fuel storage building, the wood chips will be passed through a dryer and then gravity ted into a fluidised bed combustor. Combustion gases from the combustor will then pass to the high pressure water tube boiler, raising steam. Waste steam from the process will be recyuled via an air cooled condenser, which will recycle water back into the boiler. Waste heat from the condenser would also be recycled to the fuel dryer building, thus minimising dryer energy re4uirements. A schematic of the plant layout is shown in Figure 1. ENVIRONMENTAL ASSESSMENT The assessment of the environmental impacts of the project was carried out in five stages viz: 1.

Definition of the scope of the assessment.


Definition of existing (baseline) environment.


Assessment of potential impacts and significance,


Evaluation of key issues.


Definition of mitigation requirements.


The initial scoping study required an evaluation of the engineering elements of the project, from an environmental perspective, and extensive consultation with those statutory and non statutory bodies who would be involved in the subsequent planning consent phase. These bodies involved, amongst others, the local district and county authority, the National Rivers Authority, Her Majesty!s Inspectorate of Pollution and English Nature. The scoping study thus enabled the environmental assessment team to take into account all legitimate concerns of the consultees and address these in the subsequent technical assessment.

Existing Environment The site for the proposed power plant occupies an area of approximately 2.3 ha, adjacent to the A39 trunk road at Summercourt, Cornwall. It comprises a complex mosaic of habitats on ground which has been disturbed over a number of years. Part of the site has been used for tipping waste, predominantly inert builders rubble and glass. A location plan is shown in Figure 2. The site is bounded to the north by an access road which leads directly onto the A39. To the south lies Chytane Wood. This is a disturbed woodland made up predominantly of oak/beech. The western boundary of the site is marked by a shallow stream which runs approximately north-south past the boundary. The vegetative cover on the site is dominated by bramble, Japanese Knotweed and various grasses. In the wetter parts of the site, willow carr predominates. The site lies within a predominantly agricultural area and there are various working farms in the vicinity. There is a well developed field pattern which is probably medieval in origin. The small village of Penhale lies about 1 km north of the site and further north lies the slightly larger village of Fraddon. The Indian Queens Industrial Estate, currently under development, lies some 3 km to the north.

Environmental Impacts The assessment of the environmental impacts was undertaken by initially establishing the existing baseline conditions of the site and its vicinity, followed by the prediction/quantification of the degree of change in these conditions, which would follow development of the power station. The significance of this change was then judged with reference to appropriate environmental criteria eg noise/air quality standards, or in the absence of such standards, professional judgement. The key elements reviewed during this process were: • • • • • • • • • •

Construction impacts Atmospheric emissions Noise Water quality Landscape/visual impacts Socio economics Ecological impacts Traffic Solid waste disposal Cultural heritage


Construction Construction of the power plant will take approximately 15 months. The main environmental impacts during this phase will be those associated with general construction activities and include noise, dust etc. These will be controlled through appropriate contractual conditions in Contractors' contracts. Traffic associated with the construction phase will be modest, amounting to approximately 80 vehicle movements per day (two way) at peak. The additional traffic will be insignificant in comparison with the existing flows, representing an increment of between 2-3%.

Atmospheric Emissions Combustion of the wood in the fluidised bed combustor will be designed to optimise combustion conditions and minimise pollutant production. The temperature of the combustion chamber will be not less than 850°C which is sufficient to ensure oxidation of organic contaminants such as polychlorinated dibenzodioxins and furans. The principal pollutants generated by the process will be: particulates, SO2, NOx and CO. The various quantities of pollutants discharged to atmosphere will be regulated to less than limits specified by Her Majesty's Inspectorate of Pollution (HMIP). The majority of particulates will be removed from the flue gases by a high efficiency bag filter. Residual air pollutants will be discharged via chimney approximately 26m high. The assessment of the impacts of the plant on air quality was undertaken using dispersion modelling techniques, using 'worst case' estimate of emission quantities. Both long term average and short term maxima were defined for key pollutants and the predicted values judged in relation to relevant national and international air quality criteria. The modelling studies demonstrated that none of the ground level pollutant concentrations would exceed relevant national or international air quality criteria. Air quality impacts will therefore not be significant. One of the principal benefits of the plant will be its effect on limiting CO2 production. CO 2 is one of the greenhouse gases responsible for global warming. Reductions in CO2 emissions rank high on the agenda of all industrialised countries and policies are being implemented to reduce emissions. Although CO 2 is released on combustion of all organic fuels (including wood) the amount released from the Cornwall Biomass plant will be offset by an equivalent amount fixed during the growing period of the coppice. The plant will therefore be neutral in CO2 emission terms. Emissions of CO2 will be further reduced by the displacement of some 12300 tonnes per annum of coal which would otherwise be burnt to supply the same quantity of electricity generated by the plant. This displacement will result in a nett reduction of approximately 31000 tonnes of CO 2 per annum.

Noise A variety of noise sources will be present on the site, some internal and some external. Internal noise levels will be controlled to within the limits specified in the EC Directive on noise in the workplace. The principal external noise sources are the air cooled condenser and the fuel drying equipment. Estimates of noise levels at the nearest noise sensitive receivers were made using standard acoustic prediction procedures. The noise level at the nearest permanent residential property was estimated to increase by about 2 dB(A) above the existing average night time noise level. Such an increase will not be significant in terms of nuisance effects.


Water Quality During operation, the plant will need to discharge various effluents. These include: Water treatment plant Boiler blowdown General plant drains Surface water runoff Foul water The quantities of effluent produced will be small, amounting to between 3 and 5 m 3 per day. Effluents from the water treatment plant and boiler blowdown will be similar in character being purified townswater but with a higher level of suspended solids. Boiler blowdown water will additionally be at a high temperature. To avoid any significant environmental impacts, the effluent streams will be routed to a holding tank, and in the case of any possible oil contamination, to an air interceptor prior to discharge to the stream adjacent to the site. Overall, the liquid effluent discharges were judged to be insignificant.

Landscape/Visual Impacts The introduction of an industrial facility into a predominantly rural area represented a potential concern from the visual impact point of view. The site selected for the project is well screened by woodland on three sides and is bounded by hedges and the main A39 trunk road to the east. The majority of buildings which will make up the power station are low lying (3 to 9m high) and will be effectively screened by existing vegetation. However, the boiler house, rising to 17m, and the chimney, at 27m, represent new features which will be visible outside the site boundary. Furthermore, the landform surrounding the site is undulating and rises quite steeply to the west and east which affords long range views into the site. Thus a degree of visual intrusion will result from the development of the power station. It is planned to mitigate this as far as possible through a specifically designed landscaping scheme incorporating indigenous planting to blend in with the existing woodland.

Socio Economics The potential socio economic benefits of the proposed plant are significant although this must be balanced against possible disbenefits that could arise from nuisance during construction (eg noise, dust etc) or through visual impact concerns. During construction, the plant will need to employ 40-50 persons, the majority of whom are expected to ~3e locally based. This will therefore have a short term positive benefit on reducing local unemployment. It is estimated that 10 persons will be required to operate the plant and it is expected that the majority of these could be sourced from the local area. The establishment of arable coppice on agricultural land will attract grant aid through the Woodland Grant Scheme administered by the Forestry Authority. Further grants could be available through the Set-Aside scheme. Approximately 1500-1800 ha of land will be needed to grow the coppice and total inward investment in grant aid could be of the order of £3 million. Modelling of 'ripple' effect of this grant aid suggests between 50-100 long term jobs could be provided in the agricultural

746 community. This would represent a reduction in the agricultural unemployment rate in the region of the order of 1%.

Ecological Impacts The proposed site is of limited ecological significance being predominantly low grade scrub vegetation, characteristic of wasteground. Whilst the area to the west of the site has been designated a Cornwall Nature Conservation Site (CNCS), the site itself does not fall within this, or indeed any other, conservation designation. A field survey of the site failed to identify the presence of any rare or endangered species. Whilst the development will have impacts on the existing habitat, with parts of the site being entirely covered with hard surfaces, no losses of ecologically rich habitats will arise. The more ecologically rich area to the west of the site will be preserved. No significant ecological impacts were identified.

Other Environmental Factors (i)

Traffic The principal traffic impacts will arise at the construction stage of the plant but even at this stage, impacts will be minimal due to the small volumes anticipated relative to traffic on the surrounding network. Impacts of traffic during operation will be minimal.


Solid Waste The plant will generate approximately 1-2 tonnes per day of waste ash. This will be deposited into sealed containers and removed off-site at regular intervals. Disposal will be to commercial outlets as fertilizer, or to an approved landfill if necessary.


Cultural Herita.qe The site and surrounding area have been extensively exploited in recent times although the field systems retain their medieval character. Documented settlements in the vicinity include Trefullock (1327), Trenithan (1259) and a house and chapel at Burthy. Several early tin mines are sited along a lode running roughly east-west through the site. The remnants of the Chypraze Consols mine lies immediately opposite the site access road. An archaeological assessment of the site and its environs was carried out. archaeological sites were identified on the proposed site itself.

No major

In conclusion, environmental impacts from the development and operation of the facility are all expected to be generally minimal. Positive benefits will be derived through employment potential and through reductions in greenhouse gases and other polluting emissions. A degree of visual impact will arise due to the nature of the building structures and the presence of a chimney. Whilst short range views will be effectively screened by surrounding trees/hedgerows, the plant will be visible from long range viewpoints. The development of this type of renewable energy plant represents a significant step towards establishing a new type environmentally benign energy production method in the UK.



Department of the Environment/Welsh Office: Planning Policy Guidance Note 22, Renewable Energy. (1993).


Town and Country Planning Act (Assessment of Environmental Effects) Regulations 1988. HMSO London (1988).







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