courteenhall anaerobic digestion (ad) facility local …...agrivert limited ii 402.2367.00001 local...

Courteenhall Anaerobic Digestion (AD) Facility

Local Air Quality Assessment

402.2367.00001

August 2008

Agrivert Limited i 402.2367.00001 Local Air Quality Assessment – Proposed Biogas Facility August 2008

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CONTENTS 1.0 INTRODUCTION............................................................................................................ 1

1.1 Context ................................................................................................................ 1 1.2 Scope................................................................................................................... 1 1.3 Structure of Report ............................................................................................ 2

2.0 REGULATIONS AND GUIDANCE ................................................................................ 3 2.1 UK / European Air Quality Standards and Regulations .................................. 3 2.2 Odour Regulation and Guidance ...................................................................... 5 2.3 Local Planning Policy ........................................................................................ 7

3.0 APPROACH................................................................................................................... 8 3.1 Odour................................................................................................................... 8 3.2 Combustion Products - Point sources (Gas engines) .................................... 9

4.0 BASELINE AIR QUALITY AND SITE SETTING......................................................... 10 4.1 Background Air Quality ................................................................................... 10 4.2 Topography....................................................................................................... 12 4.3 Meteorology ...................................................................................................... 12 4.4 Sensitive Receptor Locations ......................................................................... 13

5.0 ODOUR ASSESSMENT .............................................................................................. 15 5.1 Identification of Odour Sources...................................................................... 15 5.2 Assessment of Impacts ................................................................................... 16 5.3 Residual Significant Impacts........................................................................... 18

6.0 COMBUSTION PRODUCTS - POINT SOURCES ...................................................... 19 6.1 Proposed development – Point Sources........................................................ 19 6.2 Assessment of Impacts ................................................................................... 19 6.3 Residual Significant Impacts........................................................................... 25

7.0 CONCLUSIONS........................................................................................................... 26 7.1 Approach........................................................................................................... 26 7.2 Results .............................................................................................................. 26

TABLES Table 1: Air Quality Standards and Benchmarks (EALs) .................................................. 5 Table 2: Ambient Air Quality.............................................................................................. 10 Table 3: SNDC Real Time Monitoring Data....................................................................... 11 Table 4: SNDC Passive Monitoring Data .......................................................................... 11 Table 5: Discrete Receptor Locations............................................................................... 14 Table 6: Biofilter Odour Emission Calculations (per unit) .............................................. 17 Table 7: Energy Crop Silage Emission Calculations....................................................... 17 Table 8: Odour Impact at Receptor Locations ................................................................. 18 Table 9: Point Sources and Emissions............................................................................. 19 Table 10: Engine Pollutant Emissions Parameters ......................................................... 20 Table 11: Predicted Long Term Nitrogen Dioxide Impacts ............................................. 21 Table 12: Predicted Short Term Nitrogen Dioxide Impacts............................................. 22 Table 13: Predicted Long Term Sulphur Dioxide Impacts .............................................. 23 Table 14: Predicted Long Term Hydrogen Chloride Impacts.......................................... 24 Table 15: Predicted Long Term Benzo[a][Pyrene Impacts.............................................. 25

Agrivert Limited ii 402.2367.00001 Local Air Quality Assessment – Proposed Biogas Facility August 2008

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FIGURES

Figure 1: Windrose For Bedford Observation Station (1999-2003) ................................ 13

APPENDICES

Appendix A Detailed Dispersion Modelling Checklist Appendix B Detailed Dispersion Modelling Inputs

DRAWINGS

Drawing AQ1: Site Location Plan Drawing AQ2: Odour Impact Assessment Drawing AQ3: Short-term Nitrogen Dioxide Impacts Drawing AQ4: Predicted Long-term Nitrogen Dioxide Impacts

Agrivert Limited: Courteenhall AD Facility 1 402.2367.00001 Local Air Quality Assessment August 2008

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1.0 INTRODUCTION

1.1 Context

SLR Consulting have been appointed by Agrivert Ltd (Agrivert) to undertake an air quality assessment for a proposed anaerobic digestion (AD) facility located at West Lodge Farm, Courteenhall, Northamptonshire. The location of the application site is shown in Drawing AQ1.

The primary objective of this air quality assessment is therefore to determine whether the proposed development will give rise to significant air quality impacts.

This assessment quantifies and assesses the resultant impacts from the proposed development in terms of local air quality using Environment Agency and DEFRA approved techniques and then clarifies the significance of these impacts against published standards.

The report describes the assessment methodology, the baseline conditions currently existing at the application site and surroundings, the likely significant environmental impacts, the designed-in mitigation measures to prevent adverse impacts and the likely residual impacts.

1.2 Scope

The scope of the assessment has been determined in the following way:

• through pre-application discussions between Agrivert and representatives of the Northampton County Councils (NCC) planning department (who provided previous air quality assessments for proposed AD facilities);

• review of air quality data for the area surrounding the site, including data from the National Air Quality Information Archive (NAQIA), and that relating to South Northamptonshire’s District Council’s (SNDC)s Review and Assessment of air quality;

• a desk study to confirm the location of nearby areas that may be sensitive to changes in local air quality;

• review of information relating to construction and operational processes and traffic flow data; and

• reference to NCC’s and SNDC’s relevant planning policies.

1.2.1 Identification of potentially significant emissions

The following potentially significant emissions associated with the proposed AD development have been identified:

• odours arising from handling and processing of waste materials and the potential to cause annoyance in the locality of the development; and

• combustion products from point sources (i.e. gas engines) and the potential to affect local pollutant concentrations.

1.2.2 Identification of Insignificant emissions

The following potential emissions associated with the development have been classified as insignificant, and therefore not assessed further are;

• dust arising during construction and the handling and processing during the process;


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• bioaerosols released from waste treatment processes; and • exhaust emissions from vehicles associated with the site during construction and

operation.

The potential emissions of dust and bioaerosols are considered insignificant due to the small scale of construction activities, the enclosure and abatement of operational sources, and the distance to sensitive receptors. Given that all reception building air is extracted through a biofilter prior to release to atmosphere this is not considered a potential source of dust or bioaerosols (studies of enclosed composting sites have shown biofilters treating the exhaust air to typically remove more than 90% of incoming bioaerosols1). The only operational activity undertaken outside relates to the silage clamp (the majority of which would be covered), however this is a typical agricultural activity.

Emissions from traffic are considered insignificant given the low volume of traffic flows associated with the development. The maximum number of vehicle movements associated with the site would be approximately 60 vehicle movements per day. This increase of HGV traffic movements on the local road network is well below the criteria used to indicate the requirement for an air quality assessment of 200 HDV movements per day2

1.3 Structure of Report

The remainder of the report is structured as follows:

• Section 2 provides a summary of the legislation and guidelines relevant to the proposed activities at the site;

• Section 3 details the methodology applied in undertaking the assessment; • Section 4 provides a description of the surrounding environment, including the

identification of potentially sensitive receptors and a description of local climate and air quality conditions;

• Section 5 details the assessment of odour from the proposed facility; • Section 6 details the assessment of combustion products from point sources at the

proposed facility; and • Section 7 summarise the findings of the assessment.

Supporting information is provided in the Appendices.

1 Sanchez-Monedero, M.A et al. 2003. Biofiltration at composting facilities: effectiveness for bioaerosol control. Environ Sci Technol. 2003. 2 Design Manual for Roads and Bridges, Volume 11, Section 3, Part 1, HA202/07 – Ari Quality. Highways Agency May 2007.


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2.0 REGULATIONS AND GUIDANCE

This section provides a summary of the primary regulatory controls, planning policy and other relevant guidance to enable the assessment approaches to be viewed in context.

2.1 UK / European Air Quality Standards and Regulations

2.1.1 UK Air Quality Strategy (UKAQS)

The Government's policy on air quality within the UK is set out in the Air Quality Strategy for England, Scotland, Wales and Northern Ireland (UKAQS) most recently updated in July 20073. The UKAQS sets out a framework for reducing hazards to health from air pollution and ensuring that international commitments are met in the UK.

The UKAQS sets standards and objectives for ten pollutants. Standards are the concentrations of pollutants in the atmosphere which can broadly be taken to achieve a certain level of environmental quality. The standards are based on the assessment of the effects on human health (including sensitive sub groups) or ecosystems. In general, these are concentration limits, above which sensitive members of the public (e.g. children, the elderly and those of ill health) might experience adverse health effects. Objectives are policy targets often expressed as maximum concentrations not to be exceeded either without exception or with a limited number of exceedences within a specified timescale.

For some pollutants, there is both a long-term (e.g. annual mean) standard and a short-term (e.g. one hour mean) standard. These periods reflect the varying impacts on health of differing exposures to pollutants. Long-term standards are generally lower than short-term standards owing to the chronic health effects associated with exposure to low concentrations of pollutants for longer periods of time.

The UKAQS standards have been set taking into account the limit values (objectives) contained in the European Air Quality Framework Directive (Directive 96/62/EC) and the first, second, third and fourth Air Quality Daughter Directives (1999/30/EC, 2000/69/EC, 2002/3/EC and 2004/107/EC) for the protection of health and ecosystems. These standards are as described in the Air Quality Standards Regulations 2007. These standards have been used in the assessment where relevant.

2.1.2 Local Air Quality Management (LAQM)

Part IV of the Environment Act 1995 requires local authorities to periodically review and assess the quality of air within their administrative area. The reviews have to consider the present and future air quality and whether any air quality objectives prescribed in regulations are being achieved or are likely to be achieved in the future.

Where any of the prescribed air quality objectives are not likely to be achieved the authority concerned must designate an Air Quality Management Area (AQMA).

For each AQMA the local authority has a duty to draw up an Air Quality Action Plan (AQAP) setting out the measures the authority intends to introduce to deliver improvements in local air quality in pursuit of the air quality objectives. Local authorities are not statutorily obliged to meet the objectives, but they must show that they are working towards them.

3 The Air Quality Strategy for England, Scotland, Wales and Northern Ireland - Defra - July 2007.


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DEFRA has published technical guidance for use by local authorities in their review and assessment work4. This guidance, referred to in this report as LAQM.TG(03), has been used where appropriate in the assessment presented here.

DEFRA has also recently published LAQM (08) as a consultation draft which proposes a number of changes to the core guidance documents for use by persons involved in LAQM, or considering the impacts of a development with the potential to impact on air quality. However the present guidance LAQM.TG (03) has been used where appropriate in the assessment presented here.

2.1.3 Environment Agency Guidance – EPR H1

The Environmental Permitting Regulations (EPR) Horizontal Guidance Note for Environmental Risk Assessment5 (H1) provides supplementary information, relevant to all sectors, to assist Applicants in responding to the requirements described in the Environmental Permitting Regulations (2008). This document can be used to support an Environmental Assessment of the overall impact of the emissions resulting from the installation to confirm that the emissions are acceptable (i.e. do not cause significant pollution).

The H1 guidance provides the assessor with a screening methodology and Environmental Assessment Levels (EAL’s) for each pollutant against which impact may be assessed.

Emissions to air are considered to be insignificant if:

• Maximum Process Contribution (long term) ≥ 1% of the EAL; or • Maximum Process Contribution (short term) ≥ 10% EAL.

If impacts are defined as being insignificant, no further assessment is required; where they are not classified as insignificant, further assessment is required where background concentrations are considered to calculate the Predicted Environmental Concentration (PEC), i.e. the PC plus background.

Emissions to air are considered to be significant with the need for detailed modelling as follows:

• (Maximum PC (long term) + background concentration) ≥ 70% of the EAL; or • (Maximum PC (short term) + 0.2 * background concentration) ≥ 20% EAL.

Although this report is intended to support a planning application, the EPR H1 guidance represents the most appropriate source of technical guidance for modelling point source emissions.

2.1.4 Benchmarks to be used in the Assessment

Table 1 below presents a summary of the air quality benchmarks (or Environmental Assessment levels – EALs) to be used in the assessment of traffic and point source emissions. Details on odour, dust and bioaerosols are provided in their respective topic sections.

4 Department for Environment, Food and Rural Affairs (DEFRA): Part IV The Environment Act 1995 Local Air Quality Management Review and Assessment Technical Guidance LAQM.TG(03) (Feb 2003). 5 Environment Agency, EPR H1 Environmental Risk Assessment, (2008)


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Table 1: Air Quality Standards and Benchmarks (EALs)

Pollutant Concentration Measured as Reference

200 µg/m3 1-hour mean not to be exceeded more than 18 times per year (99.79%ile of hourly averages) Nitrogen dioxide

(NO2) 40 µg/m3 Annual mean

AQS

Carbon monoxide (CO) 10 mg/m3 Maximum daily running 8 hour mean AQS

350 µg/m3 1 hour mean not to be exceeded more than 24 times per year (99.73 %ile of hourly averages)

125 µg/m3 24 hour mean not to be exceeded more than 3 times per year (99.18 %ile of hourly averages)

AQS Sulphur dioxide (SO2)

50 µg/m3 Annual mean EPR H1

50 µg/m3 24-hour mean not to be exceeded more than

35 times per year (90.4 %ile of hourly averages)

Particulate matter (PM10) (gravimetric)

40 µg/m3 Annual mean

AQS

PAHs 0.25 ng/m3 Annual mean AQS

800µg/m3 Peak hourly mean Hydrogen Chloride

20µg/m3 Annual Mean EPR H1

2.2 Odour Regulation and Guidance

2.2.1 Planning Policy and General Nuisance Legislation

The main legislation that relates to the control of odour is concerned with statutory nuisance, this is contained within Part III of the Environmental Protection Act (EPA) 1990 (as amended by the Noise and Statutory Nuisance Act 1993) and allows local authorities and individuals to take action to prevent a statutory nuisance. Section 79 of the EPA defines, amongst other things, smoke, fumes, dust and smells emitted from industrial, trade or business premises so as to be prejudicial to health or a nuisance, as a potential statutory nuisance.

Planning Policy Statement 236 (PPS23) Planning and Pollution Control and Annex 1 Pollution Control and Air and Water Quality provides a list of matters to be considered in determining planning applications. Under PPS23 any potential air pollutant, dust and odour releases that could affect amenity are considered to be a material planning consideration.

2.2.2 Odour - Regulatory Standards and Guidelines

Currently, in the UK there are no statutory standards for assessing odour nuisance. On this basis, odour impact criteria are typically based upon guideline documents and case law.

Where a site falls under the Environmental Permitting Regulations as a Part I or Part II process, the site will be regulated to ensure it does not result in unacceptable levels of offsite odour impact during normal operation. This is the case for the proposed development.

6 Office of the Deputy Prime Minister: Planning Policy Statement 23: Planning and Pollution Control (Oct 2004).


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2.2.3 UK Guidance

The Environment Agency has published a number of guidance and research documents relating to odour assessment. These are typically aimed at processes falling under the Pollution Prevention and Control Act (1999), now EPR. These include the draft Horizontal Guidance Notes H47 Parts 1 and 2, which were released for consultation in 2002. Consultation responses have yet to be published at the time of writing and it is likely to be re-issued, hence this document must be used to inform the reader of principles associated with odour, rather than representing a regulatory document.

The draft IPPC H4 Guidance proposes installation-specific exposure criteria (benchmarks) on the basis that not all odours are equally offensive, and not all receptors are equally sensitive. The conditions of a Permit will balance these installation-specific exposure criteria against what is realistically achievable in accordance with the concept of Best Available Techniques (BAT).

The draft H4 Guidance proposes indicative criteria of between C98, 1 hour 1.5 ouE/m3 and C98, 1

hour 6.0 ouE/m3 as a starting point before adjustments for local factors are made, dependent upon the relative offensiveness of the source (for an explanation of conceptual basis for odour assessment and an explanation of these units refer to the methodology (Section 3.1.1).

2.2.4 UK Case-law / Common Practice

The most frequently referenced case law in the UK in relation to odour assessment is that of the Newbiggin-by-the-Sea Inquiry8, defended by Northumbrian Water Limited. As a result of this case, and in the absence of any definitive Environment Agency guidance, an impact criterion of C98, 1 hour 5.0 ouE/m3 has been frequently applied and accepted for both planning and permitting purposes in the UK, as being sufficient to prevent unacceptable odour impacts for a number of industry sectors including waste handling operations.

2.2.5 UK Water Industry Research

The other source of research into odour impacts in the UK has been the wastewater industry, which given the nature of materials processed and the open nature of treatment processes is considered to be analogous to waste management operations conducted at Courteenhall. The most in-depth study published study in the UK of the correlation between of modelled odour impacts and human response (dose-effect) was published by UK Water industry Research (UKWIR) in 20019. This was based on a review of the correlation between reported odour complaints and modelled odour impacts in relation to 9 wastewater treatment works in the UK with ongoing odour complaints.

The findings of this research indicated the following:

• At modelled exposures of below C98, 1-hour 5ouE/m3, complaints are relatively rare, at only 3% of the total registered;

7 Environment Agency, 2002: Technical Guidance Note IPPC H4. Integrated Pollution Prevention and Control, Horizontal Guidance for Odour. Part 1 – Regulation and Permitting. October 2002. 8 Department of the Environment, Northern Reg. Office, Town and Country Planning Act – Section 78, Appeal by Northumbrian Water Ltd: Land adjacent to Sipal Burn, Newbiggin-by-the-Sea, Northumberland, planning reference APP/F2930/A/92 206240, 1993. 9 Odour Control in Wastewater Treatment – A Technical Reference Document. Ref 01/WW/13/3 – UKWIR, 2001.


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• at modelled exposures between C98, 1-hour 5ouE/m3 and C98, 1-hour 10ouE/m3, a significant proportion of total registered complaints occur; 38% of the total;

• the majority of complaints occur in areas of modelled exposure greater than C98, 1-hour 10ouE/m3; 59% of the total

2.3 Local Planning Policy

2.3.1 Northamptonshire County Council

NCC Waste Local Plan

The main aim of the NCC Waste Local Plan is to encourage increased waste treatment capacity for the county and reduce the reliance on landfill. One of the proposals for the Plan is to support new technologies to manage the waste.

In terms of environmental impact, the Local Plan takes into account that any new development will have some degree of environmental impact, but that any impacts would need to be minimised.

Policies that are included within the Local Plan that relate to the environmental impacts on the aerial environment are as follows:

• Policy 8…proposals should minimise the transportation of waste associated with the proposal…;

• Policy 10…proposals will not be permitted where they would be likely to result in harm to a statutorily protected species or habitat; and

• Policy 15…where relevant proposals should mitigate, attenuate and control any…air quality [or] odours…associated with the planned development.

The Local Plan states that in relation to air quality, providing that air re-circulation and exhaust equipment are appropriately designed and regularly maintained, that emissions are unlikely to present significant environmental problems. Processes such as anaerobic digestion, as stated in the Local Plan, incorporate odour control systems and would only cause problems if the units are opened for maintenance works.

2.3.2 South Northamptonshire District Council

SNDC Local Plan, 1997.

The Local Plan for SNDC was adopted in October 1997 and, together with the Structure Plan, forms the Development Plan for the area.

One of the primary, general policies the Local Plan states in relation to when planning applications will be allowed is the condition that any development ‘is neither of a hazardous nature nor likely to cause problems of pollution, noise, vibration, smell, smoke, discharge or fumes’.


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3.0 APPROACH

The detailed assessment of potential impacts has been undertaken utilising atmospheric dispersion modelling techniques (see Appendix B for overview). The actual assessment approach is dependent on the particular pollutant as detailed in the following sections.

3.1 Odour

The odour impact assessment has used atmospheric dispersion modelling. In particular this involves estimating the potential magnitude of odour emissions from sources at the site, modelling the dispersion of odour releases in the atmosphere on the basis of meteorological data, and determining the frequency and concentration of odour at locations in the surrounding environment, particularly at local receptors (e.g. residential locations). The following sections explain in further detail the methodology employed, beginning with a description of the conceptual basis for odour assessment.

3.1.1 Conceptual Basis for Odour Assessment

The assessment of an odour impact may be undertaken with two differing approaches, by the use of indicator determinands, or total odour.

Where an emission is dominated by one particular odorous gas, the use of an indicator determinand may allow simple validation of an assessment through monitoring at source and receptor. For example, hydrogen sulphide in the case of emissions from sewage treatment works.

However, more commonly an odour is the result of a complex mixture of chemicals. On this basis, a more appropriate approach in the case of this complex gas mixture is that of total odour. Odour assessments are undertaken using the concept of the European Odour Unit (ouE), as defined in BS EN 1372510. This approach allows impact assessment of any odorous gas as it is independent of chemical constituents and centres instead on multiples of the detection threshold (i.e. the physiological response of a human) of the gas in question.

As the odour unit is a Standard Unit in the same way as gram or milligram, the notation used in odour assessment follows the conventions of any mass emission unit as follows:

• concentration: ouE/m3 • emission: ouE/s • specific emission (emission per unit area): ouE/m2/s

Like air quality standards for individual pollutants, exposure to odour is given in terms of a percentile of averages over the course of a year. This prevents results being skewed by infrequent meteorological conditions. The exposure criteria most accepted in the UK at present is given in terms of (concentration) European Odour Units as a 98th percentile (C98) of hourly averages. This allows 2% of the year when the impact may be above the limit criterion (175 hours). The notation for impact is therefore C98, 1 hour X ouE/m3.

10 BS EN 13725:2003 Air Quality – Determination of Odour Concentration by Dynamic Olfactometry


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3.1.2 Impact Criterion to be used in the Assessment

The objective of this part of the assessment is to determine the potential extent to which annoyance could reasonably be expected to occur as a result of emissions of odour from the site.

The benchmark values proposed in the draft H4 Agency Guidance document are unlikely to be adopted. This, in conjunction with a lack of explicit guidelines in finalised regulatory and guidance documentation for an impact criterion, lead us to consider that the most appropriate impact criterion to use is C98, 1 hour 5.0 ouE/m3. This would follow an approach most commonly applied and accepted in the UK to date.

However, given that the site will be regulated by the Environment Agency under the Environmental Permitting regime, a C98, 1 hour 3.0 ouE/m3 has also been investigated. This is considered appropriate given the nature of the odours released from the site i.e. biofilter and silage which would fall within the ‘medium relative offensiveness’ category defined in Appendix 6 of the draft H4 guidance.

3.2 Combustion Products - Point sources (Gas engines)

Horizontal Guidance Note EPR H1 presents a stages approach for the assessment of point source emissions. This approach ‘screens’ out pollutants that present an insignificant risk of impact (‘Tier 1’). Those pollutants that cannot be screened out as having an insignificant risk of impact progress onto a more detailed assessment such as an advanced dispersion modelling exercise (‘Tier 2’).

Due to the proximity of receptors surrounding the Application site it is considered suitable to assess all likely combustion products using an advanced dispersion model. The predicted ground level impacts have been compared to the H1 criteria to assess significance. Where the predicted Process Contribution (PC) is not classified as ‘insignificant’, consideration has been given to the background concentration of the relevant pollutant.


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4.0 BASELINE AIR QUALITY AND SITE SETTING

4.1 Background Air Quality

4.1.1 Predicted Concentrations

Predicted background concentrations for Air Quality Strategy pollutants have been calculated from the National Air Quality Archive11 UK Background Air Pollution Maps. The 1 km grid resolution maps provide 2004 background annual mean pollutant concentrations from which future concentrations are predicted by application of conversion factors detailed in LAQM.TG(03).

In respect to background concentrations, at some point during 2008 / 2009 specific background maps for each 1x1km grid square will become available as described in the draft LAQM TG(08). These are unlikely to be significantly different for rural areas and at the time of writing these maps are not available. As such, correction factors provided in LAQM TG(03) have continued to be used.

As the proposed development lies across two 1km x 1km grid squares, the estimated annual mean background concentrations have been taken from the grid square with the highest concentrations (GR 475500, 253500) and are shown in Table 2 below.

Table 2: Ambient Air Quality

Pollutant 2008

Concentration µg/m3

2009 Concentration

µg/m3

2010 Concentration

µg/m3 Nitrogen dioxide (NO2) 18.69 18.15 17.10 Carbon monoxide (CO) 174 163 155 Sulphur dioxide (SO2) (a) 2.12 (2005 data) 2.12 (2005 data) 2.12 (2005 data) Particulate matter (PM10) 20.17 19.82 19.20 Benzo-a-pyrene PAHs(b) 0.00014 0.00014 0.00014 Hydrogen Chloride(c) 0.47 0.47 0.47 Notes: (a) No method for calculating concentrations in years beyond 2005 is published. (b) Stoke Ferry monitoring site concentration for 2006. (c) Peak annual mean from Nitric Acid Monitoring Network (Site: Rothamsted) 1999 – 2006.

The estimated annual mean background concentrations for 2009 have been used in the assessment of the first full year of operation of the proposed development. In general air pollution concentrations reduce (i.e. air quality improves) with time due to predicted reductions in vehicle pollutant emissions. Assessment of 2009 rather than a later year therefore represents the ‘worst case’ year in terms of background levels of air pollutants.

4.1.2 Local Authority Review and Assessment

SNDC have declared one Air Quality Management Area as a result of elevated Nitrogen dioxide levels relating to traffic emissions in the town of Towcester. The AQMA, declared in 2005 as a result of the Progress Report, is approximately 7km southwest of the Proposed Facility.

11 www.airquality.co.uk


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Air Quality Review and Assessments undertaken since the declaration of the Towcester AQMA have concluded there is no significant risk of exceedences of any of the remaining AQS pollutants within the district.

Nitrogen dioxide concentrations are continually monitored within the AQMA and across the district where residential areas are in close proximity to busy road networks such as the M1.

SNDC Air Quality Monitoring Data

SNDC monitor Nitrogen dioxide concentrations using a real time monitor for monitoring within the AQMA and passive diffusion tubes located across the district.

Real Time Monitoring Data

SNDC operate a chemiluminescent real time monitor for monitoring Nitrogen dioxide concentrations within the Towcester AQMA. The monitor, located outside Towcester Town Hall (grid reference SP693486) has been in operation since 2005, due to poor data capture during 2005, results are only available for 2006 and 2007, as shown in Table 3 below.

Table 3: SNDC Real Time Monitoring Data

Year Annual Average (ug/m3) Average Data Capture (%) Analyser data 2006 37.4 N/A* Analyser data 2007 37.2 98.5 * Data capture from 2006 was not available

The annual mean concentrations of Nitrogen dioxide within the AQMA were recorded to be marginally below the annual mean objective of 40ug/m3. The short term objective (18 exceedences of 200ug/m3 per year) was not exceeded during 2006 and 200712.

Given that the real time monitor is located within an urban area and in excess of 5km from the application site, the results are not considered to be representative of Nitrogen dioxide levels in the locality of the proposed Facility.

Passive Monitoring Data

Nitrogen dioxide is monitored by SNDC using passive diffusion tubes at 32 locations across the district. The locations have been chosen based upon the potential for traffic related issues that may cause elevated levels of the pollutant. Diffusion tube monitoring locations within 2km of the Application Site are shown below in Table 4 for the years 2006 and 2007.

Table 4: SNDC Passive Monitoring Data

Diffusion Tube Location Classification Distance to Application

Site

2006a Annual Average (ug/m3)

2007b Annual Average (ug/m3)

Roade; 40/40a Stradford Road Roadside 1.9km 25.13 21.86 Roade; 16 London Road Roadside 1.4km 34.97 31.40 Roade; 1 London Road Roadside 1.5km 29.03 27.76

a) Annual 2006 concentrations have been bias adjusted using bias adjustment factor 0.906 b) Annual 2007 concentrations have been bias adjusted using bias adjustment factor 0.864

12 South Northamptonshire Council, Environment Division. Air Quality Progress Report May 2008.


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Given that these diffusion tube locations are at roadside locations and in close proximity to the M1 motorway, and the rural nature of the application site, concentrations in the locality of the development will be lower.

4.1.3 Background Odour

It is not possible to quantitatively measure background odour concentrations because of the low concentrations and large uncertainties in the results. Odour is therefore not routinely monitored at the site and there have been no detailed quantitative odour impact studies for the site carried out in the past.

The land surrounding the application site is predominantly agricultural; as such background odours would be typical of rural locations. These would typically include occasional odours due to agricultural practises undertaken in the local area.

4.2 Topography

The presence of elevated terrain can significantly affect the dispersion of pollutants and the resulting ground level concentration in a number of ways. Elevated terrain reduces the distance between the plume centre line and the ground level, thereby increasing ground level concentrations. Elevated terrain can also increase turbulence and, hence, plume mixing with the effect of increasing concentrations near to a source and reducing concentrations further away.

The topography of the local area is relatively flat, with ground levels reducing slightly to the north. Within 500m of the application site ground levels reduce by 25m to the north and rise by approximately 6m to the south. To the west and east directions ground levels remain relatively flat, varying by between 3m and 4m.

Topography has been incorporated into the detailed dispersion models for both combustion point sources and odour impact assessment.

4.3 Meteorology

In the UK, detailed point source (odour and air pollutants) models require 3-5 years consecutive meteorological data for one station in accordance with Environment Agency Air Quality Modelling and Assessment Unit13 (AQMAU) requirements. Following consultation with the meteorological data provider, it was concluded that Bedford Observation Station, located approximately 30km to the east of the development site, would provide the most representative data set for purposes of this assessment. A 5 year data set for this station, covering the period 1999 – 2003 has been used for this assessment. Information on wind direction frequency, wind speed, frequency of stability conditions and mixing height were obtained for the Observation Station.

13 Environment Agency Air Quality Modelling and Assessment Unit (AQMAU). Online resource, available at http://www.environment-agency.gov.uk


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A windrose for the Bedford Observation Station for the years 1999-2003, providing the frequency of wind speed and direction, is presented in Figure 1. Windroses for individual years are presented in Appendix B.

Figure 1: Windrose For Bedford Observation Station (1999-2003)

0%

2%

4%

6%

8%

10%

10 + m/s

8 - 10 m/s

6 - 8 m/s

4 - 6 m/s

3 - 4 m/s

2 - 3 m/s

0.5 - 2 m/s

<0.5m/s

The predominant wind direction is from the south south-west and southwest, producing a combined frequency of 24.8%. Winds from the north and eastern sectors are infrequent. Calm conditions (wind speeds less than 0.5 m/s) occur for approximately 2.2% of the period.

4.4 Sensitive Receptor Locations

For the purposes of this air quality assessment the term 'sensitive receptors' includes any persons, locations or ecosystems that may be susceptible to changes as a consequence of the proposed development.

According to the Local Air Quality Management Technical Guidance (LAQM.TG(03)), air quality standards should apply to all locations where members of the public may be reasonably likely to be exposed to air pollution for the duration of the relevant objective. Thus short term standards such as the 1 hour standard for NO2 should apply to footpaths at site boundaries and other areas which may be frequented by the public even for a short period of time. Longer term standards such as the 24 hour for PM10, or annual means, should apply at houses and other locations which the public can be expected to occupy on a continuous basis. These standards do not apply to exposure at the workplace.

There are no areas in the immediate vicinity (5km radius) of the Application site that have been designated for nature conservation value that warrant specific consideration of air quality impacts.

A number of discrete sensitive receptors have been selected for presentation of the air quality impacts in the surrounding area. These include representative residential properties and recreational areas (such as footpaths) in proximity to the application site. The location of the sensitive receptors considered can be seen in Drawing AQ2 and below in Table 5.


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Table 5: Discrete Receptor Locations

National Grid Reference Receptor Receptor Type

Exposure X Y

R1 West Lodge Farm Building

Agricultural Building

Short-term/transient 474980.7 253137.1

R2 Courteenhall West Lodge Residential Long-term 474893.7 253245.4

R3 West Lodge Cottages Residential Long-term 475264.4 253342.7 R4 The Lodge Residential Long-term 475345.5 253033.6 R5 Bridge Cottage Residential Long-term 474761.4 253051.4

R6 Woodleys Farm (day nursery) Residential Long-term 475320.3 252862.4

R7 Gamekeepers Cottage Residential Long-term 475717.3 253034.3 R8 Thorpewood Farm Residential Long-term 474363.1 252822.1 R9 Roade (north) Residential Long-term 475242.1 252105.9

R10 Hyde Farm Residential Long-term 474695.8 251786.9 R11 Blisworth Lodge Farm Residential Long-term 473521.4 253465.9 R12 Manor Farm Residential Long-term 474605.1 254423.8 R13 Grange Park Residential Long-term 476455.1 254437.3

R14 West Lodge Farm Building

Agricultural Building

Short-term/transient 474953.5 253091.5

In addition to these discrete receptors, addition receptors were located along the nearest area of public access i.e. road and footpaths, where short-term exposure could occur as shown in Drawing AQ1. The dispersion modelling of odour and point sources has also been completed using a receptor grid, so that concentrations can be determined at any location surrounding the site.


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5.0 ODOUR ASSESSMENT

5.1 Identification of Odour Sources

Potential odour sources associated with the proposed development have been identified by consideration of details of the operations proposed on the application site. Typically odour will potentially be generated as a result of handling and processing wastes with a biodegradable fraction and the storage of silage on site.

The aspects of the proposed development which will have the potential to generate odour beyond that which would be expected for the baseline situation are limited to the operational phase of the proposed development and are as follows:

• reception building operations (waste receipt and handling); • storage of maize (energy crop) in silage clamp; • processing of waste; and • export of digestate from storage tanks for distribution.

All other aspects of the proposed development are not considered to be significant odour sources and have not been considered further.

5.1.1 Description of Odour Sources and designed-in Mitigation

Reception Building (waste receipt and handling)

Operations including waste receipt and handling undertaken within the reception building would have the potential for odorous emissions to arise if the designed-in odour abatement technologies were absent. The designed-in mitigation measures include:

• Fast acting roller-shutting doors; • negative pressure ventilation system; and • biofiltration of extracted air prior to discharge to atmosphere.

Given the controls that would be employed, it is considered that all odorous emissions arising from the reception building would be emitted through the biofilter.

Two biofilters would be installed at the facility, to provide backup in the event of failure of one biofilter. Each biofilter would be 100m2 in area (10m x 10m) and 2m high with bark / woodchip filter material to a depth of 1.6m. Each has a treatment facility of 20,000m3 per hour, giving a retention time of approximately 30 seconds within the media, which is considered suitable for abatement of odours of this type.

Extracted air would be maintained at a suitable humidity content using a humidification chamber to ensure saturation does not occur and to avoid dust blockages. Moisture control minimises the risk of shrinkage and crusting within the biofilter material, thus ensuring that short circuiting (uneven air flow) does not occur. During prolonged hot periods of weather, a surface irrigation system would be employed if required. Replacement of the biofilter media would be undertaken as necessary, typically within the time range of 3 to 7 years.

Maize Silage Clamp

In order for the proposed facility to accept a variety of waste streams, an energy crop silage will be used in the process to act as a balancing feedstock. The energy crop silage would be


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stored on site in a silage clamp on a concrete pad and delivered on a daily basis to the energy crop reception bunker.

Odorous emissions from the storage of the maize energy crop on site would be contained using a silage ‘clamp’ system comprising of push walls and a tarpaulin cover, a similar practice to that of traditional farm silage clamps. The entire surface of the maize storage would be enclosed with the exception of the front end of the store, required for transferring the maize to the digester tanks. Effluent arising from the silage clamp would be captured by a drainage grid and used within the process.

The potential for odour emissions from the silage clamp are therefore expected to be small and only occur through the exposure of a small area of the maize to the digesters. The area of exposure would, at its maximum, be an area of 450m2 (90m x 5m).

Digesters and Storage Tanks

The anaerobic digestion process leads to the generation of volatile organic compounds, including of course methane which is fed to the gas engines. If unmitigated this source is considered to have the greatest potential to lead to the detection of odours at sensitive receptor locations with the potential to cause annoyance.

The primary and secondary digesters and storage tankers are fully contained air tight containers with the biogas (methane) extracted to gas engines. The off-gas is combusted in the gas engines which leads to the effective destruction of odorous compounds. Consequently this source is considered to be fully abated.

Removal of Digestate for Application Offsite

The product digestate is stored within large sealed tanks for up to 6 months prior to the use of this material as a ‘biofertiliser’ for crops on the adjacent farmland. As with the digesters, the storage tanks are fitted with roofs to capture any residual biogas emitted during storage to maximise energy production.

When the digestate is ready to be applied to the adjacent farmland (dependent on seasonal factors), the digestate is pumped into sealed tankers. This process is undertaken within the Reception Building. The digestate is then transported by the sealed tankers to a selected field where specialised slurry applicators apply the digestate in accordance with the relevant legislation.

The operations associated with the removal of digestate from the application site do not therefore produce any potential odorous emissions given that at every stage the digestate is held within sealed containers.

5.2 Assessment of Impacts

Following consideration of the designed-in odour abatement measures, the only potential odorous sources from the application site are the biofilters and the exposed area of the maize silage clamp which have been assessed though the application of dispersion modelling.

5.2.1 Derivation of Odour Emissions Rates

The generation of odour emissions data for the dispersion modelling has been based on values given in published literature in the UK and Europe as detailed in the following


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sections (for a more detailed description of the odour model input parameters see Appendix B).

Biofilter

As a result of the designed-in odour control at the reception building, it is considered that all emissions from the handling and processing of waste within the building would be emitted through the biofilter. Potential odorous emissions from the biofilter have been based upon results from over 150 odour concentration measurements from biofilters serving composting plants14. The odour emission is calculated based on the estimated odour concentration multiplied by the designed volume air flow through the filter.

Table 6: Biofilter Odour Emission Calculations (per unit)

Parameter Value Length (m) 10 Width (m) 10 Cross Sectional Area (m2) 100 Height of release (m) 2 Depth of biofilter media (m) 1.6 Volume of biofilter media (m3) 160 Throughput of Biofilter (each) (m3/hour) 20,000 Residence Time (s) 29 Residual Odour Concentration (ouE/m3) 1,000 Odour Emission Rate (ouE/s) 5556

Energy Crop Silage

The odour emission rate from the exposed area of the energy silage crop has been based upon professional experience from previous, similar developments such as green waste composting.

Table 7: Energy Crop Silage Emission Calculations

Parameter Value Length (m) 90 Width (m) 3 Cross Sectional Area (m2) 270 Height of release (m) 3 Specific Odour Emission Rate (ouE/m2/s) 25

5.2.2 Predicted Impacts

The odour impact of the proposed development is presented in Drawing AQ2. The predicted impact at sensitive receptor locations is presented in Table 8 below. For identified sensitive

14 Biowaste Composting - New Developments and Solutions for the Reduction of Odour Emissions - Adam Srecker Biofilter - Practical Experiences from Plant Monitoring


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receptors the minimum, maximum and annual average concentration has been presented for the 5 years of results.

Table 8: Odour Impact at Receptor Locations

Odour Concentration C98, 1 hour ouE/m3 (n=5) Receptor

Minimum Maximum Average R2 Courteenhall West Lodge 0.85 1.28 1.08 R3 West Lodge Cottages 1.39 1.95 1.63 R4 The Lodge 0.32 0.58 0.43 R5 Bridge Cottage 0.12 0.25 0.17 R6 Woodleys Farm 0.25 0.50 0.32 R7 Gamekeepers Cottage 0.08 0.13 0.10 R8 Thorpewood Farm 0.03 0.05 0.04 R9 Roade (north) 0.02 0.04 0.03 R10 Hyde Farm 0.02 0.06 0.04 R11 Blisworth Lodge Farm 0.01 0.01 0.01 R12 Manor Farm 0.01 0.02 0.02 R13 Grange Park 0.04 0.06 0.05

The results of the odour impact assessment are shown in Drawing AQ2 and indicates that there will be no exceedence of either the C98, 1 hour 5ouE/m3 or theC98, 1 hour 3ouE/m3 limit criterion at any identified sensitive receptor. The receptor location likely to experience the greatest impacts is at West Lodge Cottages at C98, 1 hour 1.63 ouE/m3, approximately 33% of the limit criterion. The impact at Receptor 2, Courteenhall West Lodge, is C98,1 hour 1.08 ouE/m3, approximately 22% of the criterion.

Approximately one third of the modelled odour impact will result from the exposed area of silage and the remainder from the treated emissions from the biofilter. On this basis, whilst offsite odours may be perceptible from time to time, the concentration and frequency of odours is considered to be acceptable.

5.2.3 Mitigation and Enhancement Measures

All mitigation measures (such as the enclosure and extraction of sources to the biofilter) are ‘designed in’ and it is therefore not appropriate to consider the impacts without them.

5.3 Residual Significant Impacts

Atmospheric dispersion modelling of the predicted impact of the proposed development after application of designed-in mitigation measure shows there are no residual significant odour impacts.


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6.0 COMBUSTION PRODUCTS - POINT SOURCES

6.1 Proposed development – Point Sources

Point sources of combustion products at the proposed development have been identified by consideration of details of the operations proposed and are as follows:

• 2 No. cogeneration Combined Heat and Power (CHP) gas engines; and • 1 No. Biogas Flare.

The following pollutants are considered to be potentially released from these sources as detailed in Table 9 below.

Table 9: Point Sources and Emissions

Source Pollutant Gas Engines NO2 PM10 SO2 CO BaP HCl Flare NO2 SO2 CO

The biogas flare will only operate in emergency and maintenance situations when biogas will be diverted from the engines to the flare. This is likely to be for less than 200 hours per year (<3% of the year) and is therefore a ‘standby’ unit. Furthermore the emission rate of pollutants from a flare is lower than those from the engines, and exhaust gases will be at higher temperatures. Emissions from the flare have therefore not been considered further in the assessment.

6.2 Assessment of Impacts

As with the odour modelling, the Atmospheric Dispersion Model used for the assessment was BREEZE AERMOD GIS version 6. For further details of the model, topographical and meteorological data and GIS capability refer to Appendix B.

6.2.1 Derivation of Pollutant Emission Rates

The emission parameters input into the dispersion model are presented in Table 10 below.

The Agency document Guidance for monitoring landfill gas engine emissions15 and monitoring research16 has been used to derive pollutant concentration for the plant as it will be powered by biogas (methane) from the anaerobic digesters, the exhaust is therefore considered likely to have similar emissions to a landfill gas engine.

15 Environment Agency, Guidance for monitoring landfill gas engine emissions LFTGN08, (September 2004) 16 Land Quality Management Ltd, Landfill Gas Engine Exhaust and Flare Emissions (September 2002)


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Table 10: Engine Pollutant Emissions Parameters

Parameters Units CHP Plant 1 CHP Plant 2 x OS (m) 475028.3 475030.2

Location y OS (m) 253136.3 253136.3

Engine - Jenbacher 320 Jenbacher 320 Stack height m 12m 12m Release temperature K 456 456 Efflux velocity m/s 28.8m/s 28.8m/s Stack diameter m 0.3 0.3 Flow rate (Actual) Am3/s 2.04 2.04 Flow rate (Normalised) Nm3/s 0.89 0.89 NOx Emission Level mg/m3 650 650 PM10 Emission Level mg/m3 10 10 BaP Emission Level mg/m3 0.001 0.001 CO Emission Level mg/m3 1500 1500 HCl Emission Level mg/m3 20 20 NOx Emission Rated g/s 0.58 0.58 PM10 Emission Rated g/s 0.01 0.01 BaP Emission Rated g/s 0.0000009 0.0000009 CO Emission Rated g/s 1.33 1.33 SO2

Emission Rate e g/s 0.07 0.07 HCl Emission Rated g/s 0.02 0.02 Reference Sources: a) Environment Agency, Guidance for monitoring landfill gas engine emissions LFTGN08, (September 2004) b) Land Quality Management Ltd, Landfill Gas Engine Exhaust and Flare Emissions (September 2002) c) Environment Agency, IPPC Sector Guidance Note – Combustion Activities, (2002) d) Emission rates of NOX, PM10, BaP, CO and HCL based upon the normalised flow rate and the relevant emission level. e) SO2 emission rate based upon a maximum concentration of 250ppm H2S in the inlet gas, representing the highest concentration before corrosive damage occurs on the engine.

Nitric Oxide to Nitrogen Dioxide Conversion

Oxides of nitrogen (NOx) emitted to atmosphere as a result of combustion will consist largely of nitric oxide (NO), a relatively innocuous gas. Once released into the atmosphere, NO is oxidised to NO2. The proportion of NO converted to NO2 depends on a number of factors including wind speed, distance from the source, solar irradiation and the availability of oxidants, such as ozone (O3).

Guidance from AQMAU17 states that ‘for short-term impacts, convert all measured or estimated nitrogen oxide emissions to NO2 and assume 50 per cent of this value when making comparisons with the short term NO2 environmental benchmark’. Therefore, the modelled NOx impact has been corrected by a factor of 0.5 to represent the impact of NO2 for short term (1-hour) impact.

17 Environment Agency Air Quality Modelling and Assessment Unit (AQMAU). Online resource, available at http://www.environment-agency.gov.uk


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Total oxidation has been assumed for comparison of predicted concentrations with the long-term objective for NO2. Therefore, 100% of the NOx value has been used to show annual average impact of NO2.

6.2.2 Dispersion Modelling Results

Nitrogen Dioxide: Long Term (annual)

The maximum predicted long term process contribution of nitrogen dioxide from the proposed development at relevant receptor locations is 6.9µg/m3, 17.3% of the EAL of 40µg/m3. The maximum Predicted Environmental Concentration (PEC) is 62.7% of the EAL and therefore long-term impacts of nitrogen dioxide are not considered to be significant (according to the H1 criteria).

As impacts are not classified as insignificant, a summary of the PC and PEC concentrations for each relevant discrete receptor is shown below in Table 11.

Table 11: Predicted Long Term Nitrogen Dioxide Impacts

Receptor PC µg/m3 PC % EAL PEC

µg/m3 PEC % EAL

R2 Courteenhall West Lodge 2.86 7.1% 21.01 52.5% R3 West Lodge Cottages 6.92 17.3% 25.07 62.7% R4 The Lodge 2.50 6.3% 20.65 51.6% R5 Bridge Cottage 1.91 4.8% 20.06 50.1% R6 Woodleys Farm 1.50 3.8% 19.65 49.1% R7 Gamekeepers Cottage 0.71 1.8% 18.86 47.1% R8 Thorpewood Farm 0.32 0.8% 18.47 46.2% R9 Roade (north) 0.24 0.6% 18.39 46.0% R10 Hyde Farm 0.26 0.6% 18.41 46.0% R11 Blisworth Lodge Farm 0.07 0.2% 18.22 45.6% R12 Manor Farm 0.17 0.4% 18.32 45.8% R13 Grange Park 0.37 0.9% 18.52 46.3% Nb, Receptors R1 and R14 are not included within assessment as they are classified as working agricultural buildings and therefore assessed for short term impacts only.

Nitrogen Dioxide: Short Term (hourly)

The maximum predicted short term process contribution of nitrogen dioxide from the proposed development at relevant receptor locations is 102.3µg/m3, 51.2% of the EAL of 40µg/m3 at the closest point of potential public exposure (Courteenhall Road). The maximum predicted PEC is 138.6µg/m3. This represents 69.3% of the EAL of 200µg/m3 and therefore short-term impacts of nitrogen dioxide are not considered to be significant (according to the H1 criteria).

As impacts are not classified as insignificant, a summary of the of PC and PEC concentrations at the relevant receptor locations is shown in Table 12.


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Table 12: Predicted Short Term Nitrogen Dioxide Impacts


µg/m3 PEC % EAL

R1 West Lodge Farm Building 31.95 16.0% 68.25 34.1% R2 Courteenhall West Lodge 29.39 14.7% 65.69 32.8% R3 West Lodge Cottages 50.12 25.1% 86.42 43.2% R4 The Lodge 39.22 19.6% 75.52 37.8% R5 Bridge Cottage 32.76 16.4% 69.06 34.5% R6 Woodleys Farm 28.43 14.2% 64.73 32.4% R7 Gamekeepers Cottage 11.07 5.5% 47.37 23.7% R8 Thorpewood Farm 7.02 3.5% 43.32 21.7% R9 Roade (north) 5.81 2.9% 42.11 21.1% R10 Hyde Farm 6.23 3.1% 42.53 21.3% R11 Blisworth Lodge Farm 1.96 1.0% 38.26 19.1% R12 Manor Farm 3.75 1.9% 40.05 20.0% R13 Grange Park 4.41 2.2% 40.71 20.4% R14 West Lodge Farm Building 60.97 30.5% 97.27 48.6% PRa Maximum at Receptor 102.30 51.2% 138.60 69.3% a) Maximum receptors taken as the nearest point of public exposure i.e. nearest public road / track in each direction from the facility and not the installation boundary

Carbon Monoxide: Short term (8 Hour Running Mean)

The maximum predicted short term process contribution of carbon monoxide from the proposed development at relevant receptor locations is 367.8µg/m3, 3.7% of the EAL for carbon monoxide of 10,000µg/m3. The impacts of carbon monoxide are therefore classified as insignificant (according to the H1 criteria) and have therefore not been reported in full.

PM10: Long Term (annual)

The maximum predicted long term process contribution of PM10 from the proposed development at relevant receptor locations is 0.12µg/m3, 0.3% of the EAL for PM10 of 40µg/m3. The long term impacts of PM10 are therefore classified as insignificant (according to the H1 criteria) and have therefore not been reported in full.

PM10: Short Term (24 hour)

The maximum predicted short term process contribution of PM10 from the proposed development at relevant receptor locations is 0.88µg/m3, 1.9% of the 24 hour EAL for PM10 of 50µg/m3. The short term impacts of PM10 are therefore classified as insignificant (according to the H1 criteria) and have therefore not been reported in full.

Sulphur Dioxide: Long term (annual)

The maximum predicted long term process contribution of sulphur dioxide from the proposed development at relevant receptor locations is 0.79µg/m3, 1.6% of the EAL for sulphur dioxide of 50µg/m3. The maximum PEC of sulphur dioxide is 2.91µg/m3. This represents 2.3% of the long term EAL for sulphur dioxide of 50µg/m3 and therefore long-term impacts of sulphur dioxide are not considered to be significant (according to the H1 criteria).


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As impacts are not classified as insignificant, a summary of the PC and PEC concentrations for each relevant discrete receptor is shown below in Table 13.

Table 13: Predicted Long Term Sulphur Dioxide Impacts


µg/m3 PEC % EAL

R2 Courteenhall West Lodge 0.33 0.65% 2.45 2.0% R3 West Lodge Cottages 0.79 1.58% 2.91 2.3% R4 The Lodge 0.29 0.57% 2.41 1.9% R5 Bridge Cottage 0.22 0.44% 2.34 1.9% R6 Woodleys Farm 0.17 0.34% 2.29 1.8% R7 Gamekeepers Cottage 0.08 0.16% 2.20 1.8% R8 Thorpewood Farm 0.04 0.07% 2.16 1.7% R9 Roade (north) 0.03 0.05% 2.15 1.7% R10 Hyde Farm 0.03 0.06% 2.15 1.7% R11 Blisworth Lodge Farm 0.01 0.02% 2.13 1.7% R12 Manor Farm 0.02 0.04% 2.14 1.7% R13 Grange Park 0.04 0.09% 2.16 1.7% Nb, Receptors R1 and R14 are not included within assessment as they are classified as working agricultural buildings and therefore assessed for short term impacts only.

Sulphur Dioxide: Short term (24 Hour Average)

The maximum predicted short term (24-hr average) process contribution of sulphur dioxide at relevant receptor locations is 3.43µg/m3, 2.7% of the EAL of 125µg/m3. The short term (24-hr average) impacts of sulphur dioxide are therefore classified as insignificant (according to the H1 criteria) and have therefore not been reported in full.

Sulphur Dioxide: Short Term (1 Hour)

The maximum predicted short term (1-hr) process contribution of sulphur dioxide at relevant receptor locations is 23.04µg/m3, 6.6% of the EAL of 350µg/m3. The short term (1-hr) impacts of sulphur dioxide are therefore classified as insignificant (according to the H1 criteria) and have therefore not been reported in full.

Hydrogen Chloride: Long Term (annual)

The maximum predicted process contribution of hydrogen chloride from the proposed development at relevant receptor locations is 0.24µg/m3, 1.2% of the EAL. The maximum PEC of hydrogen chloride is 0.71µg/m3. This represents 3.5% of the long term EAL of 20µg/m3 and therefore the long term impacts of hydrogen chloride are not significant (according to the H1 criteria).

As impacts are not classified as insignificant, a summary of the PC and PEC concentrations for each relevant discrete receptor is shown in Table 14.


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Table 14: Predicted Long Term Hydrogen Chloride Impacts


µg/m3 PEC % EAL

R2 Courteenhall West Lodge 0.10 0.5% 0.57 2.8% R3 West Lodge Cottages 0.24 1.2% 0.71 3.5% R4 The Lodge 0.09 0.4% 0.56 2.8% R5 Bridge Cottage 0.07 0.3% 0.54 2.7% R6 Woodleys Farm 0.05 0.3% 0.52 2.6% R7 Gamekeepers Cottage 0.02 0.1% 0.49 2.5% R8 Thorpewood Farm 0.01 0.1% 0.48 2.4% R9 Roade (north) 0.01 <0.1% 0.48 2.4% R10 Hyde Farm 0.01 <0.1% 0.48 2.4% R11 Blisworth Lodge Farm 0.00 <0.1% 0.47 2.4% R12 Manor Farm 0.01 <0.1% 0.48 2.4% R13 Grange Park 0.01 0.1% 0.48 2.4% Nb, Receptors R1 and R14 are not included within assessment as they are classified as working agricultural buildings and therefore assessed for short term impacts only.

Hydrogen Chloride: Short Term

The maximum predicted short term (1-hr) process contribution of hydrogen chloride at relevant receptor locations is 8.99µg/m3, 1.1% of the EAL of 800µg/m3. The short term (1-hr) impacts of hydrogen chloride are therefore classified as insignificant (according to the H1 criteria) and have therefore not been reported in full.

PAHs: Long term (annual; modelled as Benzo[a]Pyrene)

The maximum predicted process contribution of Benzo[a][Pyrene from the proposed development at relevant receptor locations is 0.011ng/m3, 4.3% of the EAL. The maximum PEC of Benzo[a][Pyrene is 0.15ng/m3, This represents 60.3% of the EAL of 0.25ng/m3 and therefore the long term impacts of Benzo[a]Pyrene are not significant (according to the H1 criteria).

As impacts are not classified as insignificant, a summary of the PEC concentrations for each relevant discrete receptor is shown in Table 15.


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Table 15: Predicted Long Term Benzo[a][Pyrene Impacts

Receptor PC ng/m3 PC % EAL PEC

ng/m3 PEC % EAL

R2 Courteenhall West Lodge 0.004 1.8% 0.144 57.8% R3 West Lodge Cottages 0.011 4.3% 0.151 60.3% R4 The Lodge 0.004 1.6% 0.144 57.6% R5 Bridge Cottage 0.003 1.2% 0.143 57.2% R6 Woodleys Farm 0.002 0.9% 0.142 56.9% R7 Gamekeepers Cottage 0.001 0.4% 0.141 56.4% R8 Thorpewood Farm <0.001 0.2% 0.141 56.2% R9 Roade (north) <0.001 0.2% 0.140 56.1% R10 Hyde Farm <0.001 0.2% 0.140 56.2% R11 Blisworth Lodge Farm <0.001 0.1% 0.140 56.0% R12 Manor Farm <0.001 0.1% 0.140 56.1% R13 Grange Park <0.001 0.2% 0.141 56.2% Nb, Receptors R1 and R14 are not included within assessment as they are classified as working agricultural buildings and therefore assessed for short term impacts only.

6.2.3 Mitigation and Enhancement Measures

All mitigation measures (such as release of combustion pollutants through elevated stacks) are ‘designed in’ and it is therefore not appropriate to consider the impacts without them.

6.3 Residual Significant Impacts

There are no significant short or long term significant residual impacts associated with combustion products from point sources.


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7.0 CONCLUSIONS

7.1 Approach

This report assesses the potential significant impacts of the proposed development in terms of Air Quality. The report describes the assessment methodology, the baseline conditions currently existing at the application site and surroundings, the likely significant source of emission, the designed-in mitigation measures and the likely residual impacts after these mitigation measures have been implemented.

The assessments have been undertaken and reported using the latest and most appropriate UK guidance and all modelling has been undertaken using appropriate models.

7.2 Results

The results of the assessment demonstrate the requirement for designed-in and ongoing operational mitigation at this site. In particular, the site has the potential to generate odours which can be effectively mitigated through correct maintenance of the odour control equipment (containment, extraction and treatment) and day-to-day operational practice (such as site cleanliness).

Subject to all appropriate mitigation described in the report being adopted at this site, it can be concluded that:

• odour impacts will be within acceptable limits and unlikely to cause annoyance; and • impacts of point source emissions of combustion products will not be significant

(according to the H1 criteria) and will be within EAL’s for all pollutants.

APPENDICIES

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APPENDIX A

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Appendix A: Detailed Modelling Inputs

Detailed Dispersion Modelling Checklist

Document EPR H1 appendix C provides guidance relating to the structure of dispersion modelling reports, and includes a dispersion modelling report checklist. to aide the reviewer to determine the appropriateness of reporting.

Dispersion model checklist

Location Map and Site Plan Included with supporting statement and Drawing AQ1

List of pollutants modelled and relevant air quality guidelines

A table of pollutants modelled and relevant EAL’s is included in the report. H1 screening was omitted with all pollutants progressing directly onto detailed modelling.

Details of modelled scenarios The scenario considering the plant running 24 hours per day 365 days per year has been considered. A precautionary approach has been adopted and flare emissions have not been considered as the flare will only be used in maintenance situations and presents less risk than other sources.

Details of relevant ambient concentrations used

All ambient concentrations were based upon background levels provided at www.airquality.co.uk .

Model description and justification

Trinity Consultants version of US EPA AERMOD v6 was used in accordance with guidance issued by the Environment Agency Air Quality Modelling Assessment Unit. This is an advanced dispersion model and appropriate for modelling situations and pollutants such as those relevant in this study.

Special model treatments used None. Table of emission parameters used

A table of emission parameters is included in the report

Details of modelled domain and receptors

A table of discrete receptors is included in the report and the following gridded receptors applied:

Odour: 2km x 2km (SW corner NGR 474050, 252200) at a resolution of 50m. Combustion sources: 3km x 3km (SW corner NGR 473500, 251700) at a resolution of 100m & a finer 1km x 1km grid (SW corner NGR 474600, 252700) with a resolution of 25m was also located over the installation.

Details of meteorological data used (including origin) and justification

AERMOD meteorological data (surface and profile files) for the five years 1999 to 2003 inclusive was obtained for Bedford Observation Station from Trinity Consultants.

Details of terrain treatment Terrain included from .ntf file SP64 Details of building treatment Buildings taken into consideration in the model using

AERMODS BPIP module are detailed in Appendix B. Sensitivity analysis No impacts are classified as significant and therefore no

sensitivity analysis has been undertaken. Assessment of impacts Impacts have been assessed against Air Quality Strategy

objectives for each pollutant where available or EALs where they are not.

APPENDIX B

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APPENDIX B

DISPERSION MODEL INPUT DATA

APPENDIX B

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Description of Atmospheric Dispersion Modelling

The Atmospheric Dispersion Model used for the assessment was BREEZE AERMOD GIS version 6, this is an advanced dispersion model and is accepted for use by the Environment Agency. The model incorporates the odour emission parameters of each source (e.g. release rate, height, and temperature), meteorological data, terrain data, sensitive receptor locations.

A number of commercially available dispersion models are able to predict ground level concentrations arising from emissions to atmosphere. No dispersion model is wholly accurate and all models will produce variations in results under certain conditions. For this assessment the AERMOD GIS PRIME model18 has been applied.

The AERMOD dispersion modelling program is widely used and accepted by the Environment Agency in the UK for undertaking such assessments and its predictions have been validated against real-time monitoring data by the USEPA19. It is therefore considered a suitable model for this assessment.

AERMOD utilises digital elevation data to determine the impact of topography on dispersion from a source. Topographical data for the site has been obtained in OS digital (.ntf) format.

AERMOD incorporates local meteorological data in order to calculate the dispersion of emissions in the environment. Five years data, covering the period 1999 to 2003 inclusive were used in the model.

AERMOD incorporates a Geographical Information System (GIS) capability. The GIS is used to register Ordnance Survey data at 1:10000 resolution. This is used to correctly register the locations of all sources and receptor locations (e.g. residencies, schools, etc).

Meteorological pre-processing

The meteorological data for Bedford Observation Station was obtained in .met format from the data supplier and converted to .the required surface and profile formats for use in AERMOD using AERMET Pro (v6.2) meteorological pre-processor.

Details specific to the exact site location are required for the pre-processing, such as latitude, longitude and surface characteristics. Given the varying nature of the surface features in the vicinity of the site, the surface characteristics were divided into five sectors and applied as shown below in accordance with the latest guidance20.

Met Data Preparation – Applied Surface Characteristics

Zone (Start)

Zone (end)

Dominant Landscape Character

Albedo Bowena Surface Roughness

0 45 Cultivated Land 0.172 45 165 Coniferous Forest 1.038

165 215 Cultivated Land

0.254 0.958

0.288

18 Software used: BREEZE AERMOD GIS Pro, v6.2. 19 AERMOD: Latest Features and Evaluation Results. USEPA Report: EPA-454/R-03-003 June 2003, (http://www.epa.gov/scram001/dispersion_prefrec.htm#aermod) 20 AERMOD Implementation guide. AERMOD implementation workgroup, USEAP. Last revised January 8, 2008.

APPENDIX B

SLR

Zone (Start)

Zone (end)

Dominant Landscape Character

Albedo Bowena Surface Roughness

215 280 Cultivated Land 0.273 280 360 Cultivated Land 0.442

a) Bowen Ration based upon assessment of land-use in 10x10km grid surrounding Application Site being 68% Cultivated Land, 23% Urban and 9% Coniferous Forest.

Windroses for Individual Years

Bedford Meteorological Station - Windrose 1999

0%

2%

4%

6%

8%

10%

10 + m/s

8 - 10 m/s

6 - 8 m/s

4 - 6 m/s

3 - 4 m/s

2 - 3 m/s

0.5 - 2 m/s

<0.5 m/s

APPENDIX B

SLR


0%

2%

4%

6%

8%

10%

10 + m/s

8 - 10 m/s

6 - 8 m/s

4 - 6 m/s

3 - 4 m/s

2 - 3 m/s

0.5 - 2 m/s

<0.5 m/s


0%

2%

4%

6%

8%

10%

10 + m/s

8 - 10 m/s

6 - 8 m/s

4 - 6 m/s

3 - 4 m/s

2 - 3 m/s

0.5 - 2 m/s

<0.5 m/s

APPENDIX B

SLR


0%

2%

4%

6%

8%

10%

10 + m/s

8 - 10 m/s

6 - 8 m/s

4 - 6 m/s

3 - 4 m/s

2 - 3 m/s

0.5 - 2 m/s

<0.5


0%

2%

4%

6%

8%

10%

10 + m/s

8 - 10 m/s

6 - 8 m/s

4 - 6 m/s

3 - 4 m/s

2 - 3 m/s

0.5 - 2 m/s

<0.5

APPENDIX B

SLR

Odour Assessment Input Data

AERMOD provides various methods for modelling different sources, such as the use of an area, point or volume source. Using an area source assumes that there is no exit velocity of the emission and does not take into account the effects of building downwash. Point sources assume the emissions has an exit velocity and models the effect of building downwash.

The energy crop silage is modelled as an area source, given its relatively low height and that any emisison would not have an exit velocity.

The biofilters would typically be seen as an area source given that each biofilter is 2m high with an area of 100m2. This model scenario however would not allow for an exit velocity to be added to the model or for the effects of building downwash to be accounted for. Although very small, the biofilters would produce gas with an exit velocity. On this basis, the biofilters as a number of point sources, thereby allowing building downwash to be taken into account.

Described below is the emission input data used for the detailed odour modelling. It has been summarised by source.

Odour Emission Rates and Release Parameters

Parameter Biofilter No. 1 Biofilter No. 2 Energy Crop Silage

Source Type Point Point Area 475018.5 475019.6 475022.6 475023.6 475019.2 475020.0

X Coordinate

475023.2 475024.0

475123.6a

253120.9 253110.9 253121.3 253111.4 253116.4 253106.6

Y Coordinate

253116.9 253107.2

253147.1a

Emission rate (ouE/s) 1389 (x4) 1389 (x4) 25 Height of release (m) 2 2 2

Dimensions (m) - - 3 x 90 Applied diameter (m) 5.64 5.64 -

Exit Velocity (m/s) 0.056 0.056 - Temperature (°C) 25 25 -

a) Coordinates taken at southern corner of source.

APPENDIX B

SLR

The following table provides a description of buildings taken into consideration in the model. A graphical presentation of the modelled buildings can be seen below.

APPENDIX B

SLR

Modelled Buildings

Building Number Tier Description X Y Height (m)

X length (m)

y Length (m) Angle (°) Radius (m)

1 1 Existing Farm Building 474924.3 253139.4 12.0 17.8 58.2 84.1 - 2 1 Engine No. 1 475023.5 253148.4 3.0 12.2 3.0 81.5 - 3 1 Engine No. 2 475027.8 253149 3.00 12.2 3.0 81.5 -

1 9.0 35.4 31.4 83.0 - 2 10.0 35.4 21.0 83.0 - 3 11.0 35.4 12.2 83.0 -

4

4

Reception Building 475024.2 253135.8

11.8 35.4 4.0 83.0 - 5 1 Energy Silage Clamp 475116.5 253153.1 3.0 90 24 41.4 -

1 5.0 - - - 16.2 2 7.0 - - - 12.0 3 9.0 - - - 9.0 4 11.0 - - - 6.0

6

5

Storage Tank 1 475001.6 253138.3

12.1 - - - 3.0 7 1 Flare 475040.5 253159.8 7.0 - - - 1.5

1 5.0 - - - 17.5 2 7.0 - - - 13.0 3 9.0 - - - 9.0 4 11.0 - - - 5.0

8

5

Secondary Digester 475076.4 475076.4

12.1 - - - 2.0 1 5.0 - - - 17.5 2 7.0 - - - 13.0 3 9.0 - - - 9.0 4 11.0 - - - 5.0

9

5

Primary Digester No. 2 475109.8 253127.3

12.1 - - - 2.0

APPENDIX B

SLR

Building Number Tier Description X Y Height (m)

X length (m)

y Length (m) Angle (°) Radius (m)

1 5.0 - - - 17.5 2 7.0 - - - 13.0 3 9.0 - - - 9.0 4 11.0 - - - 5.0

10

5

Primary Digester No. 1 475081.5 253103.2

12.1 - - - 2.0 1 5.0 - - - 16.2 2 7.0 - - - 12.0 3 9.0 - - - 9.0 4 11.0 - - - 6.0

11

5

Storage Tank 2 475008.2 253094.0

12.1 - - - 3.0 12 1 Biofilter 475015.1 253127.6 2.0 20 10 83 -

* Ground Level across site assumed to be 112.00m, thereby taking into account site works prior to construction of facility.

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