Odour and Air Quality Assessment Surrey Hill Energy ... Consultancy, Locally Delivered Odour and Air Quality Assessment Surrey Hill Energy Anaerobic Digestion Plant REC Report: 33276r1

National Consultancy, Locally Delivered

Odour and Air Quality Assessment Surrey Hill Energy Anaerobic Digestion Plant REC Report: 33276r1 Issued: 27th November 2012 Prepared for: AcrEnergy

Osprey House, Pacific Quay, Broadway, Manchester, M50 2UE Tel – 0161 868 1300 Fax – 0161 868 1301

www.recltd.co.uk

Odour and Air Quality Assessment 27th November 2012

Surrey Hill Energy Anaerobic Digestion Plant 33276

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REPORT ISSUE

Issue/revision Issue 1 Revision 2 Revision 3

Remarks -

Date 27/11/12

Prepared by Jethro Redmore

Signature

Position Manager - Air Quality Impact Group

Authorised by Paul Furmston

Signature

Position Director

Project number 33276



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EXECUTIVE SUMMARY Resource and Environmental Consultants Ltd was commissioned by AcrEnergy to undertake an Odour and Air Quality Assessment of potential emissions from the proposed Surrey Hill Energy Farm Based Anaerobic Digestion Plant on land off Coast Hill, Wotton, Surrey. Odours from a number of sources on site, as well as atmospheric emissions from the biogas engine, have the potential to cause impacts at sensitive receptors. An Odour and Air Quality Assessment was therefore undertaken to consider effects in the vicinity of the site. Potential odour emissions were defined based on the proposed plant operation and monitoring undertaken of similar materials to be used at the facility. Impacts at sensitive receptors were quantified using dispersion modelling and the results compared with the relevant odour benchmark level. Predicted odour concentrations were below the relevant benchmark level at all sensitive receptors in the vicinity of the site for all modelling years. Due to the remoteness of the development site it is not anticipated that significant odour impacts will occur at any residential location as a result of normal operations of the proposed facility. Additional consideration was provided to potential air quality impacts as a result of atmospheric emissions from the proposed biogas engine. This indicated that the relevant regulatory controls would ensure effects would not be significant at any location in the vicinity of the site.



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TABLE OF CONTENTS

1.0 INTRODUCTION 1

1.1 Background 1

1.2 Site Location and Context 1

1.3 Limitations 2

2.0 ODOUR BACKGROUND 3

2.1 Odour Legislation and Guidance 3

2.2 Odour Definition 3

2.3 Odour Impacts 3

2.4 Odour Legislative Control 4

2.5 Odour Benchmark Levels 4

3.0 ODOUR ASSESSMENT METHODOLOGY 6

3.1 Odour Sources 6

3.2 Odour Emission Rates 6

3.3 Dispersion Modelling 7

3.3.1 Modelling Scenarios 7

3.3.2 Emissions 7

3.3.3 Assessment Extents 8

3.3.4 Terrain Data 9

3.3.5 Building Effects 9

3.3.6 Roughness Length 9

3.3.7 Monin-Obukhov Length 10

3.3.8 Assessment Criteria 10

3.3.9 Meteorological Data 10

3.3.10 Modelling Uncertainty 10

4.0 ODOUR MODELLING RESULTS 12

5.0 AIR QUALITY SCREENING ASSESSMENT 13

5.1 Air Quality Legislation 13

5.1.1 European Legislation 13

5.1.2 UK Legislation 13

5.1.3 Local Air Quality Management 14

5.1.4 Industrial Pollution Control Legislation 14

5.2 Baseline 14

5.2.1 Local Air Quality Management 15

5.2.2 Background Pollutant Concentrations 15

5.3 Assessment 15

6.0 CONCLUSION 17

7.0 ABBREVIATIONS 18

APPENDICES Appendix I Figures



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1.0 INTRODUCTION 1.1 Background Resource and Environmental Consultants (REC) Ltd was commissioned by AcrEnergy to undertake an Odour and Air Quality Assessment of potential emissions from the proposed Surrey Hill Energy Farm Based Anaerobic Digestion (AD) Plant on land off Coast Hill, Wotton, Surrey. Odours from a number of sources on site, as well as atmospheric emissions from the biogas engine, have the potential to cause impacts at sensitive receptors. An Odour and Air Quality Assessment was therefore undertaken to quantify effects in the vicinity of the site. 1.2 Site Location and Context The proposed AD plant is located off Coast Hill, to the north of Surrey Hills Business Park, Wotton, at National Grid Reference (NGR): 512915, 148035. Reference should be made to Figure 1 for a map of the site and surrounding area. It is proposed to construct and operate an AD facility that will be fuelled by energy crops and farm yard manure (FYM). The biogas produced by the AD plant will be combusted within an engine to generate electricity for export to the National Grid. The process can briefly be described as:

• Feedstock - The site will operate using biomass feedstock in the form of energy crops and FYM. The energy crops will be delivered to site using a tractor and trailer during typical harvest periods prior to unloading within the silage clamp. Once full, the clamps will be covered using protective sheeting. This will form an airtight layer to minimise odour emissions and preserve the biomass throughout the year. The clamp cover will be slightly open at one end to allow access for a bucket loader, which will transfer the feedstock to the vertical mixer for approximately two to three hours per day. FYM will be delivered to site using a tractor and trailer on a daily basis. It is anticipated that one material load will be required per day. This will be directly transferred into the vertical mixer during the two to three hour loading period, removing any on site storage requirement;

• Operation - The feedstock will be digested within the plant in a completely sealed tank. The biogas produced (a mixture of methane (CH4) and carbon dioxide (CO2)) will be piped to a storage tank prior to use in the 500kW engine where it will be combusted for the generation of electricity. Exhaust gases from the engine will be dispersed via a dedicated 10m stack; and,

• Digestate - The process will create a liquid digestate which can be used as a high quality fertiliser. This will be stored within a sealed storage tank prior to pumping into tankers and delivery to the end user for field spreading during specified periods.

Reference should be made to Figure 2 for a site layout plan. The activities associated with the proposed plant are controlled under the Environmental Permitting (England and Wales) Regulations (2010) and subsequent amendments. As such, the operator will be required to obtain an Environmental Permit from the Environment Agency (EA) as the appropriate regulator prior to operation. This will ensure the plant is managed and operated in accordance with good practice guidance and reduce the potential



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for environmental impacts. The operation of the plant may result in odour emissions from a number of activities, as well as atmospheric emissions from the biogas engine. These have the potential to cause impacts at sensitive locations within the vicinity of the site and have therefore been assessed within this report. 1.3 Limitations This report has been produced in accordance with REC's standard terms of engagement. REC has prepared this report solely for the use of the Client and those parties with whom a warranty agreement has been executed, or with whom an assignment has been agreed. Should any third party wish to use or rely upon the contents of the report, written approval must be sought from REC; a charge may be levied against such approval.



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2.0 ODOUR BACKGROUND 2.1 Odour Legislation and Guidance The following legislation and guidance was used in this assessment:

• H4: Odour Management, Environment Agency, 2011;

• Odour Guidance for Local Authorities, Department for Environment, Food and Rural Affairs, 2010; and,

• Environmental Permitting (England and Wales) Regulations (2010).

2.2 Odour Definition Department for Environment, Food and Rural Affairs (DEFRA) guidance

1 defines odour as:

"An odour is the organoleptic attribute perceptible by the olfactory organ on sniffing certain volatile substances. It is a property of odorous substances that make them perceptible to our sense of smell. The term odour refers to the stimuli from a chemical compound that is volatilised in air. Odour is our perception of that sensation and we interpret what the odour means. Odours may be perceived as pleasant or unpleasant. The main concern with odour is its ability to cause a response in individuals that is considered to be objectionable or offensive. Odours have the potential to trigger strong reactions for good reason. Pleasant odours can provide enjoyment and prompt responses such as those associated with appetite. Equally, unpleasant odours can be useful indicators to protect us from harm such as the ingestion of rotten food. These protective mechanisms are learnt throughout our lives. Whilst there is often agreement about what constitutes pleasant and unpleasant odours, there is a wide variation between individuals as to what is deemed unacceptable and what affects our quality of life."

2.3 Odour Impacts The magnitude of odour impact depends on a number of factors and the potential for complaints varies due to the subjective nature of odour perception. The FIDOR acronym is a useful reminder of the factors that will determine the degree of odour pollution:

• Frequency of detection - frequent odour incidents are more likely to result in complaints;

• Intensity as perceived - intense odour incidents are more likely to result in complaints;

• Duration of exposure - prolonged exposure is more likely to result in complaints;

• Offensiveness - more offensive odours have a higher risk of resulting in complaints; and,

• Receptor sensitivity - sensitive areas are more likely to have a lower odour tolerance. It is important to note that even infrequent emissions may cause loss of amenity if odours are perceived to be particularly intense or offensive.

1 Odour Guidance for Local Authorities, Department for Environment, Food and Rural Affairs, 2010.



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The FIDOR factors can be further considered to provide the following issues in regards to the potential for an odour emission to cause a nuisance:

• The rate of emission of the compound(s);

• The duration and frequency of emissions;

• The time of the day that this emission occurs;

• The prevailing meteorology;

• The sensitivity of receptors to the emission i.e. whether the odorous compound is more likely to cause nuisance, such as the sick or elderly, who may be more sensitive;

• The odour detection capacity of individuals to the various compound(s); and,

• The individual perception of the odour (i.e. whether the odour is regarded as unpleasant). This is greatly subjective, and may vary significantly from individual to individual. For example, some individuals may consider some odours as pleasant, such as petrol, paint and creosote.

2.4 Odour Legislative Control The main requirement with respect to odour control from industrial activities is the Environmental Permitting (England and Wales) Regulations (2010) and subsequent amendments. If a process is deemed potentially odorous then the relevant regulator will usually include the following condition in the site's Environmental Permit:

"Emissions from the activities shall be free from odour at levels likely to cause pollution outside the site, as perceived by an authorised officer of the Agency, unless the operator has used appropriate measures, including, but not limited to, those specified in an approved odour management plan, to prevent or where that is not practicable to minimise the odour."

Enforcement of the condition is by the relevant regulator, either the EA for Part A(1) processes, or the Local Authority (LA) for Part (A2) and B processes. If the regulator is satisfied that odour from a facility is causing pollution beyond the site boundary then they can serve an improvement notice that requires remedial works to be undertaken to reduce impacts to an acceptable level. The measures that are deemed appropriate will depend on the industry sector and site-specific circumstances and will take costs and benefits into account. Should appropriate actions not be taken by the operator then the regulator has a number of available options, cumulating in the revocation of the Environmental Permit and cessation of all activities on site. 2.5 Odour Benchmark Levels There is no statutory limit in the UK for ambient odour concentrations, whether set for individual chemical species or for mixtures. However, the EA has issued guidance on odour

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which contains indicative benchmark levels for use in the assessment of potential impacts from facilities regulated under the Environmental Permitting (England and Wales) Regulations (2010) and subsequent amendments. Benchmark levels are stated as the 98

th percentile (%ile) of hourly mean concentrations in

2 H4: Odour Management, Environment Agency, 2011.



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European odour units (ouE) over a year for odours of different offensiveness. In practice this is the 175

th highest hourly average recorded in the year. This parameter reflects the

previously described FIDOR factors, where an odour is likely to be noted on several occasions above a particular threshold concentration before an annoyance occurs. EA odour benchmark levels are summarised in Table 1. Table 1 Odour Benchmark Levels

Relative Offensiveness of Odour Benchmark Level as 98th

Percentile of 1-hour Means (ouE/m

3)

Most offensive odours:

• Processes involving decaying animal or fish

• Processes involving septic effluent or sludge

• Biological landfill odours

1.5

Moderately offensive odours:

• Intensive livestock rearing

• Fat frying (food processing)

• Sugar beet processing

• Well aerated green waste composting

3.0

Less offensive odours:

• Brewery

• Confectionery

• Coffee roasting

• Bakery

6.0

It is considered that odours from the AD plant would be classified as 'moderately offensive' as they are likely to be similar to livestock and composting. As such, impacts have been assessed against an indicative criterion of 3.0ouE/m

3 as the 98

th percentile of 1-hour mean

concentrations.



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3.0 ODOUR ASSESSMENT METHODOLOGY The proposed AD facility may result in odour emissions during normal operations. These were assessed in accordance with the following stages:

• Identification of odour sources;

• Identification of odour emission rates;

• Dispersion modelling of odour emissions; and,

• Comparison of modelling results with relevant criteria. The following Sections outline the methodology and inputs used for the assessment. These were agreed with Thomas Allen, Environmental Health Officer at Mole Valley District Council (MVDC), on 16

th November 2012 via email.

3.1 Odour Sources Potential odour sources were identified from the process description. These included:

• Exposed silage within the clamp;

• Exposed silage during transfer from the clamp to the vertical mixer;

• Exposed FYM during transfer from off-site sources to the vertical mixer;

• Exposed material within the vertical mixer; and,

• Expelled air during the filling of the digestate tanker. Further information on the anticipated operation of the facility was provided through discussions with AcrEnergy in order to define emissions from each source in more detail. 3.2 Odour Emission Rates There are no Emission Limit Values (ELVs) for odour and since the facility is not operational, it was not possible to monitor site specific emissions. In the absence of such information, estimations of future releases from the various identified sources had to be made to inform the dispersion model. These were made based on odour monitoring data reported at similar plants and are therefore considered to provide representative inputs for an assessment of this nature. Odour emission rates are summarised in Table 2. Table 2 Odour Emission Rates

Source Odour Emission Rate

Unit Reference

Silage 20.00 ouE/m2/s Odournet UK Ltd

(1)

FYM 68.66 ouE/m2/s Institute of Animal Science and

Technology(2)

Agitated material within vertical mixer

333 ouE/m2/s Calculated from silage and FYM

emission rates

Air expelled during filling of digestate transportation tanker for removal off site

100,000 ouE/m3 Odournet UK Ltd

(3)

References: (1) Odour Impact Assessment for a proposed Crop CHP Plant at Stoke Bardolph,



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Nottinghamshire, Odournet UK Ltd. (2) Odour Evaluation of a Dairy Farm with Anaerobic Digestion, Institute of Animal Science and

Technology Universidad Politécnica de Valencia. (3) Assessment of Potential Odour Impact from a Proposed Biomass Renewable Energy Facility

in Taverham, Norfolk, Odournet UK Ltd.

Odour emissions from the silage and FYM material within the vertical mixer were multiplied by a factor of 10, as shown in Table 2, in order to provide consideration of increased releases during the agitation of material. 3.3 Dispersion Modelling Dispersion modelling was undertaken using ADMS 4 (v4.2.1), which is developed by Cambridge Environmental Research Consultants (CERC) Ltd. ADMS 4 is a short-range dispersion modelling software package that simulates a wide range of buoyant and passive releases to atmosphere. It is a new generation model utilising boundary layer height and Monin-Obukhov length to describe the atmospheric boundary layer and a skewed Gaussian concentration distribution to calculate dispersion under convective conditions. The model utilises hourly meteorological data to define conditions for plume rise, transport and diffusion. It estimates the concentration for each source and receptor combination for each hour of input meteorology, and calculates user-selected long-term and short-term averages. 3.3.1 Modelling Scenarios The scenarios considered in the modelling assessment are summarised in Table 3. Table 3 Dispersion Modelling Scenarios

Parameter Modelled As

Short Term Long Term

Odour 98%ile 1-hour mean -

3.3.2 Emissions The emission rates shown in Table 2 were utilised with the information on anticipated plant operation provided by AcrEnergy to define emissions within the dispersion model. These are summarised in Table 4. Table 4 Emissions


Unit Characteristics

Silage clamp 20.00 ouE/m2/s 180m

2 of silage closest to sensitive

receptor exposed constantly within clamp

Silage transfer 20.00 ouE/m/s Route between clamp and vertical mixer utilised for 3-hours per day



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Unit Characteristics

FYM transfer 68.66 ouE/m/s Route between site entrance and vertical mixer utilised for 3-hours per day

Agitated material within vertical mixer

333 ouE/m2/s Vertical mixer utilised for 3-hours per

day

Air expelled during filling of digestate transportation tanker for removal off site

2,500 ouE/s Constant tanker filling for 7-hours per day during February to May and August

The emission characteristics summarised within Table 4 include the following assumptions:

• The area of the silage clamp closest to the nearest sensitive receptor is constantly uncovered. The uncovered clamp area will vary throughout operation depending on the levels of stored silage. Additionally, it is estimated that between 105m

2 and

180m2 will be uncovered at any one time. As such, the assumption that 180m

2 of the

section closest to the sensitive receptors is uncovered is considered to provide a conservative over estimation;

• The silage and FYM transfer route is utilised constantly for 3-hours per day, 7-days per week. The delivery vehicles may only be at one location on either route at any time and material movement will not take place on either Saturday or Sunday. As such, the assumption that the entirety of both routes is used for the loading period 7-days per week is considered to provide a conservative over estimation; and,

• Tankers are filled constantly for 7-hours per day during the relevant spreading periods. It is anticipated that a maximum of 7-tankers will be processed per day with each taking approximately 10-minutes to fill. As such, the assumption of constant emissions for 7-hours is considered to be a conservative over estimation.

3.3.3 Assessment Extents Ambient concentrations were predicted over the area NGR: 512300, 147500 to 513300, 148500. One Cartesian grid with a resolution of 10m was used within the model to provide data suitable for plotting within the Surfer software package. A desk-top study was undertaken in order to identify any sensitive receptor locations in the vicinity of the site that required specific consideration during the assessment. Receptors are summarised in Table 5. Table 5 Sensitive Receptors

Receptor NGR (m)

X Y

R1 The Cedars 513144 148131

R2 9 The Rookery 513150 148041

R3 Tymullen 512998 147656



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Receptor NGR (m)

X Y

R4 17 Sheep House Lane 512689 147630

R5 Coast Hill 512965 148250

The sensitive receptors identified in Table 5 represent worst-case locations. However, this is not an exhaustive list and there may be other locations within the vicinity of the site that may experience odour impacts as a result of atmospheric emissions from the facility that have not been individually identified above. It should be noted that predicted odour levels at any location within the modelled area can be derived from the contour plots provided in the Figures Section. Reference should be made to Figure 3 for a graphical representation of sensitive receptor locations. 3.3.4 Terrain Data Ordnance Survey Landform Panorama terrain data was included for the site and surrounding area in order to take account of the specific flow field produced by variations in ground height throughout the assessment extents. This was pre-processed using the dedicated function within ADMS 4. 3.3.5 Building Effects The dispersion of substances released from elevated sources can be influenced by the presence of buildings close to the emission point. Structures can interrupt the wind flows and cause significantly higher ground-level concentrations close to the source than would arise in the absence of the buildings. Analysis of the site layout indicated that a number of proposed buildings should be included within the model in order to take account of effects on pollutant dispersion. Building input geometries are shown in Table 6. Table 6 Building Geometries

Building NGR (m) Height (m) Diameter/ Length (m)

Width (m) Angle (˚)

X Y

Technical building

512875.6 148035.7 5.66 16.24 11.49 0

Storage tank 512904.0 148052.4 6.90 25.50 - -

Digester tank 512935.9 148054.8 6.93 32.30 - -

3.3.6 Roughness Length A roughness length (z0) of 0.5m was used in this dispersion modelling study. This value of z0 was considered appropriate for the morphology of the assessment area due to the



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significant amount of tree cover and is suggested within ADMS 4 as being suitable for 'parkland, open suburbia'. 3.3.7 Monin-Obukhov Length The Monin-Obukhov length provides a measure of the stability of the atmosphere. The default Monin-Obukhov length (1m) within ADMS 4 was used in this dispersion modelling study. This value is considered appropriate for the nature of the assessment area and is suggested within ADMS 4 as being suitable for 'rural area'. 3.3.8 Assessment Criteria Predicted ground level odour concentrations were compared with the relevant odour benchmark level of 3.0ouE/m

3 as a 98

th percentile of 1-hour means.

3.3.9 Meteorological Data Meteorological data used in this assessment was taken from Gatwick Airport meteorological station, over the period 1

st January 2009 to 31

st December 2011 (inclusive). Gatwick Airport

meteorological station is located at NGR: 526678, 140311, which is approximately 15.9km south-east of the proposed facility. DEFRA guidance LAQM.TG(09)

3 recommends

meteorological stations within 30km of an assessment area as being suitable for detailed modelling. All meteorological data used in the assessment was provided by Atmospheric Dispersion Modelling (ADM) Ltd, which is an established distributor of meteorological data within the UK. Reference should be made to Figure 4 for wind roses of the utilised meteorological data. 3.3.10 Modelling Uncertainty Uncertainty in dispersion modelling predictions can be associated with a variety of factors, including:

• Model uncertainty - due to model limitations;

• Data uncertainty - due to errors in input data, including emission estimates, land use characteristics and meteorology; and,

• Variability - randomness of measurements used. Potential uncertainties in model results have been minimised as far as practicable and worst-case inputs used in order to provide a robust assessment. This included the following:

• Choice of model - ADMS 4 is a commonly used atmospheric dispersion model and results have been verified through a number of studies to ensure predictions are as accurate as possible;

• Meteorological data - Modelling was undertaken using three annual meteorological data sets from the closest observation site to the facility to take account of worst-case conditions;

3 Local Air Quality Management Technical Guidance LAQM.TG(09), DEFRA, 2009.



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• Plant operating conditions - Operational parameters were supplied by AcrEnergy based on similar operational facilities. As such, these are considered to be representative of likely operating conditions;

• Emission rates - Emission rates were derived from monitoring undertaken at similar facilities and are therefore considered to be representative of potential releases during normal operation;

• Receptor locations - Receptor points were included at sensitive locations to provide consideration of impacts on these areas. Odour levels at any point within the assessment extents may be derived from the relevant Figure; and,

• Variability - All model inputs are as accurate as possible and worst-case conditions were considered as necessary in order to ensure a robust assessment of potential odour concentrations.

Results were considered in the context of the relevant odour benchmark level. It is considered that the use of the stated measures to reduce uncertainty and the use of worst-case assumptions when necessary has resulted in model accuracy of an acceptable level.



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4.0 ODOUR MODELLING RESULTS Dispersion modelling of potential odour emissions was undertaken using the input data specified previously. Predicted odour concentrations at discrete receptor locations are summarised in Table 7. Table 7 Predicted Odour Concentrations

Receptor Predicted 98th

Percentile 1-hour Mean Concentration (ouE/m

3)

2009 2010 2011

R1 The Cedars 1.55 1.25 1.07

R2 9 The Rookery 0.75 0.73 0.67

R3 Tymullen 0.10 0.20 0.08

R4 17 Sheep House Lane 0.18 0.26 0.11

R5 Coast Hill 1.12 0.78 0.91

As indicated in Table 7, predicted odour concentrations were below the odour benchmark of 3.0ouE/m

3 at all sensitive receptor locations for all modelling years.

Reference should be made to Figure 5 to Figure 7 for graphical representations of predicted odour concentrations throughout the assessment extents. These indicate maximum levels in close proximity to the odour sources, particularly the silage clamp due to the large surface area, with concentrations reducing sharply over a short distance. Due to the remoteness of the proposed site it is not anticipated that significant odour impacts will occur at any sensitive location.



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5.0 AIR QUALITY SCREENING ASSESSMENT Emissions associated with the combustion of biogas within the proposed engine have the potential to cause increases in pollutant concentrations in the vicinity of the site. These have been assessed by identifying baseline conditions and the relevant regulatory controls for the plant, before considering the potential risk of exceeding the relevant air quality standards. 5.1 Air Quality Legislation 5.1.1 European Legislation European Union (EU) air quality legislation is consolidated under Directive 2008/50/EC, which came into force on 11

th June 2008. This Directive consolidated previous legislation

which was designed to deal with specific pollutants in a consistent manner and provided new air quality objectives for particulate matter with an aerodynamic diameter of less than 2.5µm. The consolidated Directives include:

• Directive 99/30/EC - the First Air Quality "Daughter" Directive - sets ambient Air Quality Limit Values (AQLVs) for nitrogen dioxide (NO2) and oxides of nitrogen (NOx), sulphur dioxide (SO2), lead and particulate matter with an aerodynamic diameter of less than 10µm;

• Directive 2000/69/EC - the Second Air Quality "Daughter" Directive - sets ambient AQLVs for benzene (C6H6) and carbon monoxide (CO); and,

• Directive 2002/3/EC - the Third Air Quality "Daughter" Directive - seeks to establish long-term objectives, target values, an alert threshold and an information threshold for concentrations of ozone in ambient air.

The fourth daughter Directive was not included within the consolidation and is described as:

• Directive 2004/107/EC - sets health-based limits on polycyclic aromatic hydrocarbons, cadmium, arsenic, nickel and mercury, for which there is a requirement to reduce exposure to as low as reasonably achievable.

5.1.2 UK Legislation The Air Quality Regulations (2010) came into force on 11

th June 2010 and transpose EU

Directive 2008/50/EC into UK law. AQLVs were published in the regulations for seven pollutants, as well as Target Values for an additional five pollutants. Critical levels for the protection of vegetation were also included for two species. Table 8 presents the AQLVs for pollutants likely to be emitted from the plant. Table 8 Air Quality Limit Values

Pollutant Air Quality Limit Value

Concentration (µg/m3) Averaging Period

NO2 40 Annual mean

200 1-hour mean; not to be exceeded more than 18 times a year



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Pollutant Air Quality Limit Value

Concentration (µg/m3) Averaging Period

SO2 125 24-hour mean; not to be exceeded more than 3 times a year

350 1-hour mean; not to be exceeded more than 24 times a year

C6H6 5 Annual mean

CO 10,000 8-hour running mean

Part IV of the Environment Act (1995) requires UK government to produce a national Air Quality Strategy (AQS) which contains standards, objectives and measures for improving ambient air quality. The most recent AQS was produced by DEFRA and published in July 2007

4. The AQS sets out Air Quality Objectives (AQOs) that are maximum ambient pollutant

concentrations that are not to be exceeded either without exception or with a permitted number of exceedences over a specified timescale. 5.1.3 Local Air Quality Management Under Section 82 of the Environment Act (1995) (Part IV) LAs are required to periodically review and assess air quality within their area of jurisdiction under the system of Local Air Quality Management (LAQM). This review and assessment of air quality involves considering present and likely future air quality against the AQOs. If it is predicted that levels at locations of relevant exposure (normally residential properties) are likely to be exceeded, the LA is required to declare an Air Quality Management Area (AQMA). For each AQMA the LA is required to produce an Air Quality Action Plan, the objective of which is to reduce pollutant concentrations in pursuit of the AQOs. 5.1.4 Industrial Pollution Control Legislation Atmospheric emissions from industry are controlled in the UK through the Environmental Permitting (England and Wales) Regulations (2010) and subsequent amendments. The facility will be classified as a specific activity under the Regulations and as such will operate under the requirements of an Environmental Permit as defined by the EA. Amongst conditions of operation will be stated ELVs for various pollutants produced by the process. Compliance with these conditions must be demonstrated through periodic monitoring requirements, which have been set in order to limit potential impacts in the surrounding area. 5.2 Baseline Existing air quality conditions in the vicinity of the proposed development site were identified in order to provide a baseline for assessment. These are detailed in the following Sections.

4 The Air Quality Strategy for England, Scotland, Wales and Northern Ireland, DEFRA, 2007.



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5.2.1 Local Air Quality Management As required by the Environment Act (1995), MVDC has undertaken Review and Assessment of air quality within their area of jurisdiction. This process has indicated that concentrations of all pollutants considered within the AQS are currently below the relevant AQLVs and as such no AQMAs have been designated within the district. 5.2.2 Background Pollutant Concentrations Predictions of background pollutant concentrations on a 1km by 1km grid basis have been produced by DEFRA for the entire of the UK to assist LAs in their Review and Assessment of air quality. The proposed development site is located in grid square NGR: 512500, 148500. Data for this location was downloaded from the DEFRA website

5 for the purpose of

this assessment and is summarised in Table 9. Table 9 Predicted Background Pollutant Concentrations

Pollutant Predicted Background Concentration (µg/m3)

NO2 11.68

SO2 2.84

CO 263

C6H6 0.239

It should be noted that concentrations of NO2 were predicted for 2012, whilst C6H6 was for 2010 and SO2 and CO was for 2001. These were the most recent predictions available from DEFRA at the time of assessment and are therefore considered to provide a reasonable representation of background concentrations in the vicinity of the site. As indicated in Table 9, background concentrations are low and a significant increase in pollution levels would be required to result in AQLV exceedences. 5.3 Assessment The operation of the AD facility may result in air quality impacts as a result of atmospheric emissions associated with the combustion of biogas. These will be emitted through a dedicated 10m stack which exceeds the minimum EA height requirement for biogas engines. Concentrations of pollutants in the exhaust gases will be controlled to the levels shown in Table 10 through a condition of the Environmental Permit. Table 10 Pollutants and Emission Limit Values

Parameter Emission Limit Value (mg/m3)

NOx 500

SO2 350

5 http://laqm1.defra.gov.uk/review/tools/background.php.



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Parameter Emission Limit Value (mg/m3)

Total non-methane volatile organic compounds (NMVOCs)

75

CO 1,400

The ELVs shown in Table 10 have been defined by the EA based on Best Available Technique (BAT) for the sector to ensure environmental impacts are not significant at any location within the vicinity of the site. Annual stack emissions monitoring will be required as a condition of the Environmental Permit to ensure the ELVs are not exceeded during normal operation. The results will be submitted to the EA and subject to associated verification procedures. As identified previously, baseline pollution levels in the vicinity of the site are low, with a large change in concentrations necessary to result in exceedences of the relevant AQLVs. Additionally, the closest residential receptor is approximately 230m from the biogas engine stack. This provides a significant buffer zone to allow for emission dispersion. It is considered unlikely that atmospheric emissions from the combustion of biogas within the engine will result in significant air quality impacts in the vicinity of the site due to the following factors:

• Legislative control of emissions through the Environmental Permit;

• Low baseline pollution levels; and,

• Distance to the closest sensitive receptor. As such, planning consent should not be restricted on air quality grounds.



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6.0 CONCLUSION REC Ltd was commissioned by AcrEnergy to undertake an Odour and Air Quality Assessment of potential emissions from the proposed Surrey Hill Energy Farm Based AD Plant on land off Coast Hill, Wotton, Surrey. Odours from a number of sources on site, as well as atmospheric emissions from the biogas engine, have the potential to cause impacts at sensitive receptors. An Odour and Air Quality Assessment was therefore undertaken to consider effects in the vicinity of the site. Potential odour emissions were defined based on the proposed plant operation and monitoring undertaken of materials similar to those to be used on site. These were represented within a dispersion model produced using ADMS 4. Impacts at sensitive receptors in the vicinity of the site were quantified and the results compared with the relevant odour benchmark level. Predicted odour concentrations were below the relevant benchmark level of 3.0ouE/m

3 at all

sensitive receptors in the vicinity of the site for all modelling years. Maximum levels were predicted in close proximity to the odour sources, particularly the silage clamp, with concentrations reducing sharply over a short distance. Due to the remoteness of the proposed site it is not anticipated that significant odour impacts will occur at any sensitive location. Additional consideration was provided to potential air quality impacts as a result of atmospheric emissions from the proposed biogas engine. This indicated that the relevant regulatory controls, as well as the rural nature of the development, would ensure effects would not be significant at any location in the vicinity of the site.



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7.0 ABBREVIATIONS %ile Percentile AD Anaerobic Digestion ADM Atmospheric Dispersion Modelling AQLV Air Quality Limit Value AQMA Air Quality Management Area AQO Air Quality Objective AQS Air Quality Strategy BAT Best Available Technique C6H6 Benzene CERC Cambridge Environmental Research Consultants CH4 Methane CO Carbon monoxide CO2 Carbon dioxide DEFRA Department for Environment, Food and Rural Affairs EA Environment Agency ELV Emission Limit Value EU European Union FYM Farm yard manure LA Local Authority LAQM Local Air Quality Management MVDC Mole Valley District Council NGR National Grid Reference NO2 Nitrogen dioxide NOx Oxides of nitrogen REC Resource and Environmental Consultants SO2 Sulphur dioxide z0 Roughness length



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Documents

Odour and Air Quality Assessment Surrey Hill Energy ... Consultancy, Locally Delivered Odour and Air Quality Assessment Surrey Hill Energy Anaerobic Digestion Plant REC Report: 33276r1