Odour Assessment Rugeley Anaerobic Digestion Plant

www.red-env.co.uk

Odour Assessment

Rugeley Anaerobic Digestion Plant

Client: Wolseley Park Energy Ltd

Reference: 1214-2r2

Date: 4th September 2018

http://www.red-env.co.uk/


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Report Issue

Report Title: Odour Assessment - Rugeley Anaerobic Digestion Plant

Report Reference: 1214-2

Report Version Issue Date Issued By Comments

1 24th August 2018 Jethro Redmore Draft for comment

2 4th September 2018 Jethro Redmore -

Heliport Business Park, Liverpool Road, Manchester, M30 7RU

[email protected] | 0161 706 0075 | www.red-env.co.uk

This report has been prepared for Redmore Environmental Ltd in accordance with the agreed terms and conditions of

appointment. Redmore Environmental Ltd cannot accept any responsibility for any use of or reliance on the contents of

this report by any third party.


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Executive Summary

Redmore Environmental Ltd was commissioned by Wolseley Park Energy Ltd to undertake an

Odour Assessment in support of a proposed anaerobic digestion plant on land off Lichfield Road,

Rugeley.

Odours from a number of sources on site have the potential to cause impacts at sensitive

locations. An Odour Assessment was therefore undertaken to quantify effects in the vicinity of the

facility.

Potential odour releases were defined based on the size and nature of the proposed plant.

Impacts at sensitive receptors were quantified using dispersion modelling, the results compared

with the relevant odour benchmark level and significance assessed in accordance with the

appropriate guidance.

Predicted odour concentrations were below the relevant benchmark level at all sensitive

locations in the vicinity of the site for all modelling years. Resultant impacts were classified as not

significant in accordance with the stated criteria. As such, potential odour emissions from the

facility are not considered to represent a constraint to the proposed development.


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Table of Contents

1.0 INTRODUCTION 1

1.1 Background 1

1.2 Site Location and Context 1

2.0 ODOUR BACKGROUND 4

2.1 Odour Definition 4

2.2 Odour Impacts 4

2.3 Odour Legislative Control 5

2.4 Odour Benchmark Levels 6

2.5 National Planning Policy 8

2.6 Institute of Air Quality Management Guidance 8

3.0 METHODOLOGY 10

3.1 Introduction 10

3.2 Odour Sources 10

3.3 Odour Emission Rates 12

3.4 Dispersion Modelling 13

Modelling Scenarios 14

Emissions 14

Assessment Area 17

Terrain Data 18

Building Effects 19

Meteorological Data 19

Roughness Length 20

Monin-Obukhov Length 20

Modelling Uncertainty 20

3.5 Significance of Odour Impacts 21

4.0 ASSESSMENT 23

4.1 Predicted Odour Concentrations 23

4.2 Impact Significance 24

5.0 CONCLUSION 26

6.0 ABBREVIATIONS 27


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1.0 INTRODUCTION

1.1 Background

1.1.1 Redmore Environmental Ltd was commissioned by Wolseley Park Energy Ltd to undertake

an Odour Assessment in support of a proposed anaerobic digestion (AD) plant on land

off Lichfield Road, Rugeley.

1.1.2 Odours from a number of sources on site have the potential to cause impacts at sensitive

locations. An Odour Assessment was therefore undertaken to quantify effects in the

vicinity of the facility.

1.2 Site Location and Context

1.2.1 The facility is located on land off Lichfield Road, Rugeley, Staffordshire, at National Grid

Reference (NGR): 402930, 319885. Reference should be made to Figure 1 for a map of the

site and surrounding area.

1.2.2 It is proposed to construct and operate an AD plant that will be fuelled by biomass

feedstock in form of energy crops, farm yard manures, food waste, potato starch and fruit

waste. The majority of the biogas produced by the AD process will be upgraded for

injection into the gas grid. A proportion of the biogas will be combusted within a

Combined Heat and Power (CHP) unit to generate electricity.

1.2.3 The process can briefly be described as follows:

• Feedstock - The site will operate using biomass feedstock in the form of energy crops,

farm yard manures, food waste, potato starch and fruit waste. The crops will be

transported to site by tractors and trailers during typical harvest periods prior to

unloading within the two silage clamps. Once full, the clamps will be covered using

protective sheeting. This will form an airtight layer to minimise emissions, ensure the

silaging process can complete and preserve the feedstock throughout the year. The

clamp cover will be slightly open at one end to allow access to the feedstock for

transportation via a tractor and grab into the feed hopper. The potato starch and

fruit waste will be transported to site in covered vehicles and stored on the clamp

area. Any material stored on the clamp will be covered and a proportion transferred


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via a tractor and grab into the feed hopper on a daily basis. Farm yard manures will

be imported to site in covered vehicles and deposited on the clamp for

acceptance testing, before transfer into the hopper. The feed systems will be fitted

with lids. As such, once these are closed emissions from this part of the process will be

effectively contained. Food waste will be delivered as a pumpable slurry and

transferred directly into the pre-storage tank;

• Operation - The feedstock will be digested within the plant in completely sealed

tanks. The biogas produced (a mixture of methane (CH4) and carbon dioxide (CO2))

will be stored in the fermenters prior to upgrade and injection into the grid or for use

in the CHP unit where it will be combusted for the generation of electricity. A flare is

also included at the plant for emergency venting of biogas during abnormal

operation; and,

• Digestate - The process will create digestate which can be used as a high quality

fertiliser. Animal manures and slurries, as well as many other types of AD feedstock,

including energy crops, are rich in plant nutrients. These remain within the material

throughout the process, making digestate a valuable biofertiliser. By making the best

possible use of digestate as a biofertiliser, nutrients are returned to the land through

natural cycles to replace the input of inorganic fertiliser. Recycling in this way closes

a loop to create more sustainable agricultural production systems. Digestate will be

split into solid and liquid fractions using a screw separator or similar prior to land

application as part of the agricultural cycle. This part of the process will be

undertaken in accordance with the Nitrate Pollution Prevention Regulations (2008)

(as amended) and the Code of Good Agricultural Practice for Farmers, Growers and

Land Managers produced by the Department for Environment, Food and Rural

Affairs (DEFRA)1.

1.2.4 Reference should be made to Figure 2 for a site layout plan.

1.2.5 The activities associated with the proposed plant are controlled under the Environmental

Permitting (England and Wales) Regulations (2016) 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

1 Protecting our Water, Soil and Air: A Code of Good Agricultural Practice for Farmers, Growers and Land

Managers, Department for Environment, Food and Rural Affairs, 2009.


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the plant is managed and operated in accordance with good practice guidance and

reduce the potential for environmental impacts.

1.2.6 The operation of the plant may result in odour emissions from a number of activities. These

have the potential to cause impacts at sensitive locations within the vicinity of the site

and have therefore been assessed within this report.


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2.0 ODOUR BACKGROUND

2.1 Odour Definition

2.1.1 DEFRA guidance2 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."

2.2 Odour Impacts

2.2.1 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,

as outlined below, 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;

2 Odour Guidance for Local Authorities, DEFRA, 2010.


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• 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.

2.2.2 It is important to note that even infrequent emissions may cause loss of amenity if odours

are perceived to be particularly intense or offensive.

2.2.3 The FIDOR factors can be further considered to provide the following factors in regard 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.

2.3 Odour Legislative Control

2.3.1 The main requirement with respect to odour control from industrial activities is the

Environmental Permitting (England and Wales) Regulations (2016) and subsequent

amendments. If a process is deemed potentially odorous then the relevant regulator will

usually include an appropriate condition in the site's Environmental Permit to restrict

impacts beyond the facility boundary.

2.3.2 Enforcement of the condition is by the relevant regulator, either the EA for Part A(1)

processes, or the Local Authority 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


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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.

2.4 Odour Benchmark Levels

2.4.1 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

odour3 which contains indicative benchmark levels for use in the assessment of potential

impacts from industrial facilities.

2.4.2 Benchmark levels are stated as the 98th percentile (%ile) of hourly mean concentrations in

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

this is the 175th 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 %ile of 1-hour Means

(ouE/m3)

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

3 H4: Odour Management, EA, 2011.


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Relative Offensiveness of Odour Benchmark Level as 98th %ile of 1-hour Means

(ouE/m3)

Less offensive odours:

• Brewery

• Confectionery

• Coffee roasting

• Bakery

6.0

2.4.3 Odours from the facility would be classified as 'moderately offensive' as they are likely to

be similar to green waste composting and livestock rearing. As such, an assessment

criterion of 3.0ouE/m3 as the 98th %ile of 1-hour mean concentrations has been utilised

throughout this report.

2.4.4 In order to provide some context to the odour benchmark values, DEFRA have provided

the following descriptors4:

• 1ouE/m3 is the point of detection;

• 5ouE/m3 is a faint odour; and,

• 10ouE/m3 is a distinct odour.

2.4.5 An odour at a strength of 1ouE/m3 is in reality so weak that it would not normally be

detected outside the controlled environment of an odour laboratory by the majority of

people (that is individuals with odour sensitivity in the "normal" range - approximately 96%

of the population5). It is important to note that these values are based on laboratory

measurements and in the general environment other factors affect our sense of odour

perception. These include:

• The population is continuously exposed to a wide range of background odours at a

range of different concentrations, and usually people are unaware of there being

any background odours at all due to normal habituation. Individuals can also

develop a tolerance to background and other specific odours. In an odour

laboratory the determination of detection threshold is undertaken by comparison

with non-odorous air, and in carefully controlled, odour-free, conditions. Normal




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background odours such as those from traffic, vegetation, grass mowing etc, can

provide background odour concentrations from 5 to 60ouE/m3 or more6;

• The recognition threshold may be about 3ouE/m3 7:, although it might be less for

offensive substances or higher if the receptor is less familiar with the odour or

distracted by other stimuli; and,

• An odour which fluctuates rapidly in concentration is often more noticeable than a

steady odour at a low concentration.

2.5 National Planning Policy

2.5.1 The revised National Planning Policy Framework8 (NPPF) was published in July 2018 and

sets out the Government's core policies and principles with respect to land use planning,

including air quality. The document includes the following considerations which are

relevant to the proposed development:

"The planning system should contribute to and enhance the natural and local

environment by: […]

Preventing both new and existing development from contributing to or being put

at unacceptable risk from, or being adversely affected by unacceptable levels of

soil, air, water or noise pollution or land instability"

2.5.2 The implications of the NPPF have been considered throughout this assessment.

2.6 Institute of Air Quality Management Guidance

2.6.1 The Institute of Air Quality Management (IAQM) published the 'Guidance on the

Assessment of Odour for Planning'9 document on 20th May 2014. This was updated in

201810 and specifically deals with assessing odour impacts for planning purposes, namely



8 NPPF, Ministry of Housing, Communities and Local Government, 2018.

9 Guidance on the Assessment of Odour for Planning, IAQM, 2014.



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potential effects on amenity. The assessment methodology outlined in the guidance has

been utilised in throughout this report where relevant.


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3.0 METHODOLOGY

3.1 Introduction

3.1.1 The facility may result in odour emissions during normal operation. 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.

3.1.2 The following Sections outline the methodology and inputs used for the assessment.

3.2 Odour Sources

3.2.1 Potential odour sources were identified from the proposed facility layout and operating

procedures. These included:

• Exposed feedstock within the clamps;

• Exposed feedstock during transfer to the hoppers;

• Exposed material within the hoppers;

• Exposed solid digestate within the separation area;

• Air expelled from the digestate tanker during filling; and,

• Off-gas from the upgrading unit.

3.2.2 Further information on the anticipated operation of the facility was provided through

discussions with Wolseley Park Energy Ltd in order to define emissions from each source in

more detail.

3.2.3 It should be noted that the actual AD process itself is sealed and therefore does not form

a source of odour, or other emissions such as CH4 or hydrogen sulphide (H2S) under

normal operation. Should releases of these species occur then this would indicate a fault

with the plant and immediate remedial measures would be taken to eliminate the

problem to avoid affecting the AD process, with associated financial consequences for

the operator. Similarly, the CHP unit and flare will only emit products of combustion which


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do not typically have any associated odour. As such, they have not been considered as

potential sources in the context of this assessment.

3.2.4 The plant is designed to process industrial food waste which will be received in the form of

pumpable slurries. These will be pumped directly to pre-storage tank upon delivery. The

arrangement is a closed system and as such the material will not be exposed to

atmosphere. Air will not be displaced from the tank as all material is balanced throughout

the process. Therefore there will not be any emissions from this part of the process.

3.2.5 Feedstock delivery of energy crops, potato starch and fruit waste will only be undertaken

for short-periods, with materials quickly covered once deposited in the clamps. Odour

emissions from these sources are therefore likely to be short in duration and controlled

effectively once the relevant materials are contained. As such, they are not anticipated

to be significant in the context of the other sources considered with the assessment and

were not included within the dispersion model.

3.2.6 Delivery of farm yard manures will be undertaken every 10-days. These will be transferred

to site in covered 29-tonne Heavy Goods Vehicles (HGVs) or tractor and trailers and

deposited on one of the clamps for acceptance testing and quarantine. It is anticipated

that the material will remain on the clamp for a maximum of 4-hours before it is

transported using a tractor and grab into the hopper. The length of time the manures are

left exposed will be minimised as far as practicable to limit emissions from this source.

Once the material is enclosed in the hopper the lid will be shut, effectively controlling any

releases from this part of the activity.

3.2.7 Digestate will be split into solid and liquid fractions using a screw separator. Emissions from

this activity are anticipated to be negligible as the unit is enclosed. Liquid digestate will

be stored in sealed tanks prior to transfer off-site. As such, releases will only occur when air

is expelled from the tanker during filling for subsequent removal. This source was therefore

included in the model. Solid digestate will fall from the separator for storage in the

separation area prior to transfer off-site. This source was therefore also included in the

model.

3.2.8 A proportion of the biogas produced from the AD process will be upgraded for injection

into the gas grid. This involves stripping out impurities, mainly CO2, specific Volatile

Organic Compounds (VOCs) and H2S, on an activated carbon filter before treatment


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with an odorant and transfer off-site. CO2 is odourless and therefore emissions of this

species will not cause adverse impacts. The majority of VOCs and H2S will be absorbed

onto the activated carbon and not released to atmosphere. However, there is the

potential for trace amounts of residual impurities within the emissions. These have

therefore been considered further through dispersion modelling.

3.3 Odour Emission Rates

3.3.1 There are no emission limit values 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 based on odour monitoring data reported at

similar facilities and the technical specification for a comparable gas upgrading unit. As

such, they are 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

Maize silage 20.0 ouE/m2/s Odournet UK Ltd(1)

Maize 18.7 ouE/m2/s Resource and Environmental

Consultants Ltd(2)

Maize, rye, barley, sugar beet,

fodder beet, grass and other

whole crops

20.0 ouE/m2/s ADAS(3)

Maize 20.0 ouE/m2/s SKM Enviros(4)

Digestate tanker 10,000 ouE/m3 Odournet UK Ltd(5)

Dewatered digestate 2.8 ouE/m2/s Odournet UK Ltd(5)

Chicken manure 75.0 ouE/m2/s Odournet UK Ltd(6)

Cattle manure 0.8 ouE/m2/s Odournet UK Ltd(6)

Pig manure 1.35 ouE/m2/s P.D.Le et al(7)

Waste vegetables 10.0 ouE/m2/s Odournet UK Ltd(5)

Waste fruit 30.0 ouE/m2/s Popławska A et al(8)

Gas upgrading unit 228.0 ouE/s Redmore Environmental Ltd(9)


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

Odournet UK Ltd.

(2) Odour Assessment Biomass Renewable Energy Unit Spring Farm, Taverham, Resource and

Environmental Consultants Ltd.

(3) An Odour Impact Study for a Proposed Agricultural Anaerobic Digester at Cleat Hill Farm, Haunton,

ADAS.

(4) Odour and Bioaerosol Risk Assessment, Proposed Anaerobic Digestion, Whitwell, Derbyshire, SKM

Enviros.

(5) Odour Impact Assessment for a proposed Anaerobic Digestion facility in Chatteris, Cambridgeshire,

Odournet UK Ltd.

(6) Odour Impact Assessment for a proposed Anaerobic Digestion facility near Kenninghall, Norfolk,

Odournet UK Ltd.

(7) Interactive effects of dietary crude protein and fermentable carbohydrate levels on odour from pig

manure, P.D. Le, A.J.A. Aarnink, A.W. Jongbloed, C.M.C. van der Peet-Schwering, N.W.M. Ogink,

M.W.A. Verstegen, Science Direct.

(8) Application of Odour Predictions to Spatial Planning, the Case of Agricultural Biogas, Oniszk-

Popławska A., Kulig A., Chemical Engineering Transactions.

(9) Odour Assessment - Anaerobic Digestion Plant, Brigg Lane, Bonby, Redmore Environmental Ltd,

2017.

3.3.2 A number of farm yard manures will be utilised on site. For the purpose of the modelling it

was assumed that all of the material consisted of chicken manure, which was identified

as having the greatest odour potential of various animal wastes. This was considered to

provide a suitably robust assumption for an assessment of this nature.

3.3.3 Table 2 shows that maize, grass and rye and similar feedstocks are likely to have

comparable odour generating characteristics. As such, an emission rate of 20ouE/m2/s

was applied to all energy crops in the dispersion model.

3.3.4 An emission rate for potato starch could not be identified for use in the model. As such, a

general vegetable waste value was used in lieu of other information. This is considered a

reasonable assumption in the context of potato odour potential when compared with

other types of vegetables.

3.4 Dispersion Modelling

3.4.1 Dispersion modelling was undertaken using ADMS-5.1 (v5.1.2.0), which is developed by

Cambridge Environmental Research Consultants (CERC) Ltd. ADMS-5 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


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height and Monin-Obukhov length to describe the atmospheric boundary layer and a

skewed Gaussian concentration distribution to calculate dispersion under convective

conditions.

3.4.2 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.

3.4.3 The model requires input data that details the following parameters:

• Assessment area;

• Process conditions;

• Pollutant emission rates;

• Terrain information;

• Building dimensions;

• Meteorological data;

• Roughness length; and,

• Monin-Obukhov length.

3.4.4 These are detailed in the following Sections.

Modelling Scenarios

3.4.5 The scenarios considered in the modelling assessment are summarised in Table 3.

Table 3 Assessment Scenarios

Parameter Modelled As

Short Term Long Term

Odour 98th %ile 1-hour mean -

Emissions

3.4.6 The data shown in Table 2 was utilised with additional information provided by the plant

operator to define emissions within the dispersion model. These are summarised in Table 4.


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Table 4 Modelled Odour Emissions

Source Odour

Emission

Rate

Unit Characteristics

Silage in clamp 20.0 ouE/m2/s 214m2 of material exposed constantly

within the clamp

Silage transfer to

hopper

20.0 ouE/m2/s Route between clamp and feed hopper

utilised for 7-hours per day

Potato starch in

clamp

20.0 ouE/m2/s 23m2 of material exposed constantly

within the clamp

Waste fruit in clamp 30.0 ouE/m2/s 68m2 of material exposed constantly

within the clamp

Waste fruit transfer to

hopper


utilised for 7-hours per day

Material in feed

system 1

200.0 ouE/m2/s Feed hopper utilised for 7-hours per day

Material in feed

system 2

750.0 ouE/m2/s Feed hopper utilised for 7-hours per day

Manure on clamp 75.0 ouE/m2/s Manure present for 4-hours, once per

week

Manure transfer to

hopper


utilised for 2-hours, once per week

Solid digestate

storage

2.8 ouE/m2/s 97m2 of material constantly exposed

within the separation area

Digestate tanker 242.0 ouE/s Tanker is filled for 2-hours per day

Gas upgrading unit 228.0 ouE/s Constant emissions

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

• The silage face is located in the area of the clamp closest to the nearest sensitive

receptor and is constantly uncovered. The clamp face will vary throughout

operation depending on the levels of stored feedstock. Additionally, it is estimated

that a maximum of 214m2 will be uncovered at any one time. As such, the

assumption that 214m2 of the section closest to the sensitive receptors is constantly

uncovered is considered to provide a conservative over estimation;

• 23m2 of potato starch is constantly uncovered. The area of exposed material will

vary throughout operation depending on the amount stored on site. This value


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represents the maximum anticipated quantity and is therefore considered to provide

a conservative over estimation;

• 68m2 of fruit waste is constantly uncovered. The area of exposed material will vary

throughout operation depending on the amount stored on site. This value represents

the maximum anticipated quantity and is therefore considered to provide a

conservative over estimation;

• Emissions from the feed hoppers only consist of the most odourous materials to be

loaded into each system, which were silage and farm yard manures. This was

considered to provide a conservative over estimation as emissions from less

odourous feedstocks were not included;

• Emissions from the farm yard manure on the clamp occur for 4-hours, once per week

whilst acceptance testing and quarantine is undertaken;

• Emissions from the manure transfer route occur for 2-hours, once per week after

delivery and acceptance testing;

• Odour emissions from silage and farm yard manures within the feed systems were

multiplied by a factor of 10 in order to provide consideration of increased releases

during the agitation of material;

• The silage and waste fruit feedstock transfer routes are utilised constantly for 7-hours

per day. The routes were defined as 2m wide line sources between the uncovered

clamp and fruit waste and the relevant hoppers. The tractor grab may only be at

one location on the route at any time. As such, the assumption that the routes are

used for the entire loading period is considered to provide a conservative over

estimation;

• 97m2 of solid digestate is constantly uncovered in the separation area. The amount

of exposed material will vary throughout operation depending on the amount stored

on site. This value represents the maximum anticipated quantity and is therefore

considered to provide a conservative over estimation; and,

• It was assumed that digestate tankers are filled constantly for 2-hour per days. It is

anticipated that a maximum of four tankers will be processed per day, each taking

approximately 10-minutes to fill. As such, the assumption of constant emissions for 2-

hours per day is considered to be a conservative over estimation.

3.4.8 Reference should be made to Figure 3 for a graphical representation of the source

locations.


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Assessment Area

3.4.9 The assessment area was defined based on the facility location, anticipated pollutant

dispersion patterns and the positioning of sensitive receptors. Ambient concentrations

were predicted over NGR: 402180, 319140 to 403680, 320640. One Cartesian grid with a

resolution of 10m was used within the model to produce data suitable for contour plotting

using the Surfer software package.

3.4.10 Reference should be made to Figure 3 for a graphical representation of the assessment

grid extents.

3.4.11 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. The

sensitivity of each receptor was defined based upon the guidance provided within the

IAQM document 'Guidance on the Assessment of Odour for Planning'11. This recommends

that the assessor uses professional judgement to identify where on the spectrum between

high and low sensitivity a receptor lies, taking into account the principles summarised in

Table 5.

Table 5 Odour Receptor Sensitivity

Sensitivity Description

High Surrounding land where:

• Users can reasonably expect enjoyment of a high level of amenity; and,

• People would reasonably be expected to be present here continuously, or at

least regularly for extended periods, as part of the normal pattern of use of the

land

Examples may include residential dwellings, hospitals, schools/education and

tourist/cultural

Medium Surrounding land where:

• Users would expect to enjoy a reasonable level of amenity, but would not

reasonably expect to enjoy the same level of amenity as in their home; or,

• People would not reasonably be expected to be present here continuously or

regularly for extended periods as part of the normal pattern of use of the land

Examples may include places of work, commercial/retail premises and

playing/recreation fields



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Sensitivity Description

Low Surrounding land where:

• The enjoyment of amenity would not reasonably be expected; or,

• There is transient exposure, where the people would reasonably be expected

to present only for limited periods of time as part of the normal pattern of use of

the land

Examples may include industrial use, farms, footpaths and roads

3.4.12 The identified sensitive receptors and associated sensitivity are summarised in Table 6.

Table 6 Sensitive Receptor Locations

Receptor NGR (m) Sensitivity

X Y

R1 Residential - Orchard Lane 402652.5 320086.9 High



R4 Residential - Mill House 402294.0 319914.6 High

R5 Residential - Bellamour Lane 402722.7 320565.3 High

R6 Residential - Wharf Cottage 403629.7 320157.1 High

R7 Residential - Levett Grange 403558.2 319568.4 High

R8 Residential - Bower Lane 403509.0 319433.7 High





3.4.13 Reference should be made to Figure 4 for a map of the receptor locations.

Terrain Data

3.4.14 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


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variations in ground height throughout the assessment extents. This was pre-processed

using the dedicated function within ADMS-5.

Building Effects

3.4.15 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.

3.4.16 Analysis of the site layout indicated that a number of structures should be included within

the model in order to take account of effects on pollutant dispersion. Input geometries

are shown in Table 7.

Table 7 Building Geometries

Building NGR (m) Height

(m)

Length /

Diameter

(m)

Width (m) Angle ()

X Y

Fermenter 2 402932.6 319919.2 13.7 26.0 --- ---

Fermenter 1 402966.9 319903.0 10.0 33.0 --- ---

Buffer tank 402907.5 319914.9 8.0 2.8 --- ---

Gas upgrading system 402878.0 319921.4 3.6 15.9 2.8 206.2

Pre storage tank 402914.0 319906.9 4.0 9.0 --- ---

Meteorological Data

3.4.17 Meteorological data used in the assessment was taken from East Midlands Airport

meteorological station over the period 1st January 2013 to 31st December 2017 (inclusive).

East Midlands Airport observation station is located at NGR: 445745, 326055, which is

approximately 43.8km north-east of the facility. It is anticipated that conditions would be

reasonably similar over a distance of this magnitude. The data was therefore considered

suitable for an assessment of this nature.


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3.4.18 All meteorological files used in the assessment were provided by Atmospheric Dispersion

Modelling Ltd, which is an established distributor of data within the UK. Reference should

be made to Figure 5 for wind roses of utilised meteorological records.

Roughness Length

3.4.19 A roughness length (z0) of 0.2m was used within the model. This value of z0 is considered

appropriate for the morphology of the area and is suggested within ADMS-5 as being

suitable for 'agricultural areas (min)'.

Monin-Obukhov Length

3.4.20 The Monin-Obukhov length provides a measure of the stability of the atmosphere. A

minimum Monin-Obukhov length of 10m was used in the dispersion modelling study. This

value is considered appropriate for the nature of the area and is suggested within ADMS-

5 as being suitable for 'small towns <50,000'.

Modelling Uncertainty

3.4.21 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,

operational procedures, land use characteristics and meteorology; and,

• Variability - randomness of measurements used.

3.4.22 Potential uncertainties in the model results were 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-5 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;


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• Meteorological data - Modelling was undertaken using five annual meteorological

data sets to take account of a range of conditions. The assessment was based on

the worst-case year to ensure maximum concentrations were considered;

• Surface characteristics - The z0 and Monin-Obukhov length were determined for

both the dispersion and meteorological sites based on the surrounding land uses

and guidance provided by CERC;

• Plant operating conditions - Information was provided by the Wolseley Park Energy

Ltd to describe the activities and associated durations associated with the facility. As

such, these are considered to be representative of likely operating conditions;

• Emission rates - Emission rates were derived from monitoring undertaken at similar

facilities. As such, they are considered to be representative of potential releases

during normal operation;

• Receptor locations - A Cartesian Grid was included in the model in order to provide

suitable data for contour plotting. Receptor points were also included at sensitive

locations to provide additional consideration of these areas; 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

pollutant concentrations.

3.4.23 Results were considered in the context of the relevant odour benchmark level and IAQM

criteria. 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.

3.5 Significance of Odour Impacts

3.5.1 The significance of impacts was assessed through the interaction of the predicted 98th

%ile of 1-hour mean odour concentrations and receptor sensitivity, as outlined in the

IAQM guidance12 for odours of moderate offensiveness. The relevant assessment matrix is

summarised in Table 8.



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Table 8 Odour Impact

Odour Exposure Level as

98th %ile of 1-hour Means

(ouE/m3)

Receptor Sensitivity

Low Medium High

Greater than 10 Moderate Moderate Substantial

5 - 10 Slight Moderate Moderate

3 - 5 Negligible Slight Moderate

1.5 - 3 Negligible Negligible Slight

0.5 - 1.5 Negligible Negligible Negligible

Less than 0.5 Negligible Negligible Negligible

3.5.2 The IAQM guidance13 states that an assessment must reach a conclusion on the likely

significance of the predicted impact. Where the overall effect is moderate or substantial,

the effect is likely to be considered significant, whilst if the impact is slight or negligible,

the impact is likely to be considered not significant. It should be noted that this is a binary

judgement of either it is significant or it is not significant. This has been considered to

determine the overall significance of potential odour impacts associated with the facility.



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4.0 ASSESSMENT

4.1 Predicted Odour Concentrations

4.1.1 Dispersion modelling of potential odour emissions was undertaken using the input data

specified previously. Predicted odour concentrations at the discrete receptor locations

are summarised in Table 9. It should be noted that the odour concentrations are

presented as a 98th %ile of 1-hour mean values over the relevant assessment year.

Table 9 Predicted Odour Concentrations

Receptor Predicted 98th %ile 1-hour Mean Odour Concentration

(ouE/m3)

2013 2014 2015 2016 2017

R1 Residential - Orchard Lane 0.81 0.73 0.80 0.80 0.65



R4 Residential - Mill House 0.25 0.23 0.22 0.25 0.15

R5 Residential - Bellamour Lane 0.13 0.18 0.15 0.15 0.16

R6 Residential - Wharf Cottage 0.19 0.21 0.20 0.23 0.21

R7 Residential - Levett Grange 0.26 0.24 0.26 0.28 0.25

R8 Residential - Bower Lane 0.20 0.20 0.22 0.23 0.22





4.1.2 As indicated in Table 9, predicted odour concentrations were significantly below the EA

odour benchmark of 3.0ouE/m3 at all locations for all modelling years. It should be noted

that the lower EA odour benchmark value of 1.5ouE/m3 was also achieved at all

receptors.


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4.1.3 Reference should be made to Figure 6 to Figure 10 for graphical representations of

predicted odour concentrations throughout the assessment extents. These indicate

maximum levels in close proximity to the odour sources with levels reducing sharply over a

short distance.

4.2 Impact Significance

4.2.1 The significance of predicted odour impacts at the sensitive receptors is summarised in

Table 10.

Table 10 Predicted Odour Impacts

Receptor Odour Exposure

Level as 98th

%ile of 1-hour

Means (ouE/m3)

Receptor

Sensitivity

Significance of

Impact

R1 Residential - Orchard Lane 0.5 - 1.5 High Negligible

R2 Residential - Orchard Lane 0.5 - 1.5 High Negligible

R3 Residential - Orchard Lane Less than 0.5 High Negligible

R4 Residential - Mill House Less than 0.5 High Negligible

R5 Residential - Bellamour Lane Less than 0.5 High Negligible

R6 Residential - Wharf Cottage Less than 0.5 High Negligible

R7 Residential - Levett Grange Less than 0.5 High Negligible

R8 Residential - Bower Lane Less than 0.5 High Negligible





4.2.2 As indicated in Table 10, the significance of odour impacts as a result of the development

was predicted to be negligible at all receptors.


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4.2.3 The IAQM guidance14 states that only if the impact is greater than slight, the effect is

considered significant. As such, impacts are considered not significant, in accordance

with the stated methodology. Additionally, given that the concentrations are below the

EA benchmark level and the maximum impact predicted at the receptors is negligible, it

is not anticipated that significant impacts will occur at any sensitive location during

operation of the development.



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5.0 CONCLUSION

5.1.1 Redmore Environmental Ltd was commissioned by Wolseley Park Energy Ltd to undertake

an Odour Assessment in support of a proposed AD plant on land off Lichfield Road,

Rugeley.

5.1.2 Odours from a number of sources on site have the potential to cause impacts at sensitive

receptors. An Odour Assessment was therefore undertaken to quantify effects in the

vicinity of the facility.

5.1.3 Potential odour releases were defined based on the size and nature of the proposed AD

plant. These were represented within a dispersion model produced using ADMS-5.

Impacts at sensitive receptor locations in the vicinity of the site were quantified, the results

compared with the relevant odour benchmark levels and the significance assessed in

accordance with the IAQM guidance.

5.1.4 Predicted odour concentrations were below the relevant EA odour benchmark level at all

receptors for all modelling years. The significance of predicted impacts was defined as

negligible at all receptors. In accordance with the stated guidance, the overall odour

effects as a result of the proposed AD plant are considered to be not significant.

5.1.5 Based on the assessment results, potential odour impacts are not considered a constraint

to the facility.


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6.0 ABBREVIATIONS

AD Anaerobic digestion

CERC Cambridge Environmental Research Consultants

CH4 Methane

CHP Combined Heat and Power

CO2 Carbon dioxide

DEFRA Department for Environment, Food and Rural Affairs

EA Environment Agency

H2S Hydrogen sulphide

IAQM Institute of Air Quality Management

NGR National Grid Reference

VOC Volatile Organic Compound

z0 Roughness length

%ile Percentile


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Odour Assessment Rugeley Anaerobic Digestion Plant

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