odour assessment rugeley anaerobic digestion plant
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www.red-env.co.uk
Odour Assessment
Rugeley Anaerobic Digestion Plant
Client: Wolseley Park Energy Ltd
Reference: 1214-2r2
Date: 4th September 2018
Date: 4th September 2018
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Page i
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
info@red-env.co.uk | 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
4 Odour Guidance for Local Authorities, DEFRA, 2010.
5 Odour Guidance for Local Authorities, DEFRA, 2010.
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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
6 Odour Guidance for Local Authorities, DEFRA, 2010.
7 Odour Guidance for Local Authorities, DEFRA, 2010.
8 NPPF, Ministry of Housing, Communities and Local Government, 2018.
9 Guidance on the Assessment of Odour for Planning, IAQM, 2014.
10 Guidance on the Assessment of Odour for Planning, IAQM, 2018.
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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
30.0 ouE/m2/s Route between clamp and feed 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
75.0 ouE/m2/s Route between clamp and feed 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
11 Guidance on the Assessment of Odour for Planning, IAQM, 2018.
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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
R2 Residential - Orchard Lane 402674.0 320164.9 High
R3 Residential - Orchard Lane 402630.4 320250.3 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
R9 Residential - Bower Lane 403417.5 319316.8 High
R10 Residential - Bower Lane 403326.1 319241.6 High
R11 Residential - Bower Lane 403254.4 319179.1 High
R12 Residential - Bower Lane 403497.4 319510.2 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.
12 Guidance on the Assessment of Odour for Planning, IAQM, 2018.
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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.
13 Guidance on the Assessment of Odour for Planning, IAQM, 2018.
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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
R2 Residential - Orchard Lane 0.67 0.57 0.71 0.74 0.60
R3 Residential - Orchard Lane 0.42 0.35 0.42 0.43 0.37
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
R9 Residential - Bower Lane 0.16 0.13 0.15 0.17 0.16
R10 Residential - Bower Lane 0.13 0.11 0.14 0.15 0.13
R11 Residential - Bower Lane 0.12 0.11 0.12 0.14 0.11
R12 Residential - Bower Lane 0.25 0.25 0.26 0.28 0.27
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
R9 Residential - Bower Lane Less than 0.5 High Negligible
R10 Residential - Bower Lane Less than 0.5 High Negligible
R11 Residential - Bower Lane Less than 0.5 High Negligible
R12 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.
14 Guidance on the Assessment of Odour for Planning, IAQM, 2018.
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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
Date: 4th September 2018
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Figures
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