Ricardo-AEA
Review of odour monitoring and control techniques at
rendering plants
Nigel Gibson
www.ricardo-aea.com
© Ricardo-AEA Ltd
Who am I
I have been involved with odour measurement, modelling and control since 1991
and now run one of the UK’s UKAS accredited olfactometry labs.
My experience with this topic area is based on work at a number of rendering
plants:
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Alba Proteins (formerly Wildriggs).
A Hughes and Son, animal rendering facility, Skellingthorpe.
Banham Compost (formerly Pimlotts).
Chetwynd Animal by-Products, Cardigan.
Fairfield Piggeries.
Fats and Protein, Lancaster.
John Knights ABP
Mayfield Rendering, Bromsgrove.
JG Pears animal rendering facility, Newark and Market Harborough.
Peninsular Protein, Great Torrington, Devon.
P Waddington animal by-products facility, Bradford.
Sun Valley foods, Hereford.
Isle of Man Animal By Products plant.
National By-Products (Ireland).
My work extends to providing expert support for operators, regulator and
stakeholders
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Overview of session
• Project context
• Background,
• Objectives.
• What’s in the report,
• Its structure,
• Contents,
• Key findings,
• Recommendations.
• Delegates are expected to have read
the report, so today’s presentation
will only provide an overview of the
project deliverable
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Before we start ……..
Just to remind ourselves why we are here
• All rendering plants have the potential to emit offensive odour, but not all odour emitted
from a rendering plant is equally offensive.
• Regulators need to implement IPPC/IED [EPR 2010]. The key requirements to be
addressed are:
– Best Available Techniques (BAT) should be applied in relation to preventative
measures against pollution.
– No significant pollution should be caused.
– The permit should include all measures necessary for compliance, including in
situations other than normal operating conditions.
This report shows that with careful design of the plant and full commitment from the
operator a rendering plant can be operated without causing significant numbers of odour
complaints
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Background to the project
• Rendering facilities account for a large proportion of
all complaints received from members of the public.
• The public expects regulators to deal effectively
with odour levels they find unacceptable – treating
these odours as pollution and taking appropriate
enforcement action to ensure that operators deal
with the sources of odour in a timely fashion (or
temporarily or permanently shutting down these
facilities if they are either unwilling or incapable of
bringing the impact of odour emissions to a level
that is considered acceptable).
• Cost regulation?
• Need a good grasp of what BAT is in terms of
odour control?
• Need good understanding of objective odour
assessment techniques?
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Background to the project
• Dealing effectively with odour levels that the
public finds unacceptable is fairly
straightforward when a facility operator is
violating specific conditions of their permit.
• This may not always be the case. The source
of an offensive odour may not be readily
identifiable, or is an occasional emission from
non-contained sources where either the
facility is operating within its permit conditions
or the relevant condition is a general ‘odour
boundary’ condition.
• Need for practical odour management and
control
• Understanding what has worked
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Background to the project
• Compliance violations involve the regulator
taking some sort of action against the facility
operator – frequently in response to a
complaint from the public.
• When odour releases are slight or negligible
and the facility operator is in compliance, then
more effective engagement with the impacted
public by both the regulator and the facility
operator may be the most appropriate
strategy.
• Not all odour from a rendering plant are highly
offensive therefore there is a need to manage
stakeholder expectation?
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Background to the project
• A regulator has to balance site regulation with
stakeholder expectation.
• Some stake holder comments [not included in
the report]:
“Intensity of odour has also declined but the
intensity of the smell varies, but on most
occasions it is sufficiently strong to make you gag.
Moreover, the emissions affect your mental and
physical well being, depress your appetite, and
force you to remain indoors (although the smells
often penetrate into even a modern, doubleglazed home).”
“Sheer frustration dealing with terrible odours.
Lack of respect for residents by the Plant
management.”
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Overall objective of the project
1. To identify best practice for implementing existing
guidance for the control and monitoring of odour
emissions, and recommend additional activities that
complement and enhance existing guidance and
improve performance.
The report
• Seeks to elaborate on the technical guidance that has
been prepared by Europe and transpose through national
sector guidance.
• Uses case studies to reinforce best practice.
• Purely provides supporting material.
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Overall objective of the project
2. To take stock of the legal landscape with regard to
odour, and identify, explain, and recommend
specific, objective and concrete permit conditions
that can be used to deal with any unacceptable
levels of offensive odour.
The report goes on to look at the types of legal action
involving odour. This is designed to show you the types
of problems encountered elsewhere and how they were
dealt with.
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Overall objective of the project
3. To assess odour control techniques/technologies, in order to aid their effective and
appropriate application.
The report provides advice on techniques/technologies used to minimise odour emission.
We provide some technical material on the techniques/technologies, and give an
indication of how effective it has been. We also give some advice on what to watch out
for and also how to monitor the situation.
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Structure of report
• General introduction
• BAT for odour control – UK and Ireland
• Background information on the rendering sector – the process, odour emission and
complaint scenarios
• Sections covering the implementation of BAT for odour control
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–
–
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Acceptance, reception, handling and storage of raw material
Containment
Active odour abatement systems (normal/abnormal conditions, process/foul/building ventilation odour)
Inspection and maintenance
• Compliance monitoring
• Management of odour
• Summary of recent odour cases
• Appendices covering
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–
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Provisions of SG8 relevant to BAT for odour control at rendering facilities
The determination of the exhaust ventilation rates
Example planned preventative maintenance schedule
Example odour diary sheet
An example site inspection report for a rendering plant
Outline odour management plan
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Data sources for report
The report draws on a number of information sources
• Literature search
– We tried to identify papers which dealt with odour management on rendering plants.
We were particularly interested in finding out how regulators deal with odour from
rendering outside Europe.
– Following conversation with US regulators it was apparent that
• The focus of control objectives was different [ground water rather than odour]
• Published guidance was relatively old [1974 !?!]
• Odour control requirement and objective were less stringent than in Europe.
• We contacted supplier of abatement plant but were unable/unwilling to supply any
information.
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Data sources for report …… cont.
• Results of the survey
– The survey captured information on a variety of plant characteristics:
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Site description
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Information on odour control plant (normal and abnormal operation)
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Raw material management and control of supply chain
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Understanding risk of odour emission
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Building design and managing negative pressure within buildings
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Approach taken to setting stack heights from all odour control plant
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Routine monitoring of odour and complaints investigation
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Approach to public engagement
•
Approach taken to dealing with any odour incidents
– In England & Scotland the survey was filled out by Regulators.
– In Ireland the survey was filled out by both the Regulators and Operators.
– In Republic of Ireland an additional questionnaire was sent to community groups, but
was not included in the report.
– Data was provided on 25 installations.
– A summary of the information provided is included at appropriate points in the report.
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Data sources for report …… cont.
• Existing guidance material [Slaughterhouse/Animal By-Products BREF ]
– This document is the primary information source used to establish BAT for the
sector.
– Key information was extracted from this document along with references to aid
navigation of the BREF,
• Other guidance material [food/drink/milk BREF]
– Document used to provide information on certain odour control techniques.
• Experience of TAG/Link members.
– There is a wealth of information held by regulators on the management and control
of odour at rendering plants.
– Within the limitation of this type of project some of this information has been
incorporated in the report.
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Section on BAT for odour control
States the overall objectives that operators must comply
with.
• Sector guidance note SG8
Source  pathway  receptor
– Odour boundary condition, plus
– Variety of other requirements designed to ensure
compliance with the OBC. Based on requirements of
BREF.
• Irish BAT note
– Defines specific benchmarks of <1.5 ouE/m3 as a
98th%ile 1 hour for new plant or <5 ouE/m3 as a
98th%ile 1 hour for existing plant, plus
– Variety of other requirements designed to ensure
compliance with the odour benchmark taken directly
from the BREF.
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Section on the rendering process/sector
• Provides a simple outline of the process:
– Raw material reception
– Storage and handling of raw materials
– Size reduction of raw materials
– Processing of materials
– Post-processing of materials
– Treatment of odorous emissions
– Storage of processed materials
– Washing and cleaning
– Effluent treatment (on site or to discharge)
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Section on the rendering process/sector …… cont.
• Lists the range of possible sources of odour:
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Excessive build-up of raw materials or excessive residence time of raw materials at the site prior to processing
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Inadequate control of odours during receipt and processing of odorous material
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Inadequate building containment and/or air extraction
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Loss of negative pressure in buildings through open doors, windows and compromised structural integrity
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Accidental loss of containment from failed plant and equipment (e.g. extraction system failure)
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Failure/Bypass of arrestment equipment resulting in discharge of odorous air or water effluent (eg. TO trip, Backup system)
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Conveyor systems (e.g. raw material conveyors)
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Open vessels (e.g. effluent treatment plants, lagoons)
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Storage areas (e.g. raw materials reception)
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Storage vessels (e.g. tallow storage)
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Loading and unloading of vehicles
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Vehicle washing areas
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Pipework and ductwork systems (e.g. pumps, valves, flanges, pressure relief valves, catchpots, drains, inspection hatches,
etc.)
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Spillages and leaks
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Contaminated surfaces, build-up of residues
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Condensate production and handling
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Burning of poor quality tallow.
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Section on the rendering process/sector …… cont.
• Background on the type of odorants emitted:
– Sulphur, nitrogen and oxygen containing compounds
– Aliphatic & aromatic hydrocarbons (fats and oils)
• Lists the common odour descriptor assigned to
emissions:
– ‘burnt meat/chicken’, ‘dog food’, ‘burnt fat’, ‘pork scratchings’,
‘OXO cubes’, and ‘rotten vegetables’
• Provides a simple odour balance to apportion
odour to the main emission types.
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Section on the rendering process/sector …… cont.
Data extracted from survey returns:
• Relationship between distance to nearest
receptor and number of complaints:
– Data shows that rendering plants can
operate without causing complaint.
• Relationship between number of complaints
and plant throughput:
– Data shows that the number of
complaints received is not proportional to
capacity.
• Complaints – Not an accurate measure
– Fatigue of complainants
– Planned changes
– Weather dependant (temp/wind direction)
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Implementation of BAT – what we cover
Section split into the following areas:
• Acceptance, reception, handling, and storage of raw material
• Containment
• Active odour control systems:
– Performance of odour-control systems treating process vapour and foul odour
(cooking, pressing, and sterilising)
– Treating low-intensity high-volume building extraction air
– Emission control during abnormal operation
• Maintenance.
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Implementation of BAT – what report provides
• Each section
– Gives practical background information on the topic area
• Why we are concerned with the topic
• Factors that influence odour generation or performance
• Any specific features that you should pay particular attention to
• Where appropriate references to sections of the BREF.
– Includes tables which cross reference with BREF, SG8 and Irish BAT note.
– A summary of relevant information submitted through the survey.
– Indicates the practical steps that could be considered to mitigate odour.
– Gives practical advice in the form of simple case studies. These case studies were
developed with the help of TAG/LINK members and direct contact with certain
operators.
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Implementation of BAT – raw materials
• Odour associated with the handling and
storage of raw materials is directly linked to
the decomposition process that
commences as an animal, fish, or bird is
slaughtered or dies.
• The rate of degradation is most affected by
the temperature under which the material is
stored, but the rate will also be influenced
by the nature of the waste material, and
how it is stored and handled while at the
slaughterhouse.
• Thus odour mitigation must focus on raw
material quality
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Implementation of BAT – raw materials
• In general terms, the potential effects of raw material quality on odour will be:
– Relatively low where rendering is located close or adjacent to the slaughtering
or processing, and there is a relatively quick and direct flow of raw material to
the rendering facility.
– Relatively high in circumstances where:
• raw material has been rejected on the basis of its quality and odour;
• there is a delay in transfer and/or inadequate temperature control before
rendering raw material, especially during warm weather;
• where raw material is stored at a bulking up and mixing temporary facility
prior to arriving on site; and
• where material has travelled some considerable distance.
• Other related factors such as increased moisture (e.g. if a TO is employed) or
higher BOD/COD (e.g. if water is treated on site) may be important
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Implementation of BAT – raw materials
Aspect
Where does the raw material come from?
How many sites have formal mechanisms for controlling the quality
of raw materials entering the site?
Does this mechanism material to be rejected on grounds of odour?
Time period before dispatch
Storage arrangements while awaiting dispatch
If raw material is rejected from a particular source, would this
prohibit that source from supplying material in future?
On arrival is the raw material immediately unloaded in the raw
material area?
Is raw material allowed to be stored outside?
If raw material is allowed to be stored outside how many delivery
vehicles are allowed on site and for how long?
Are the same raw-material handling systems applied to all raw
material types handled on site?
Additional material provided
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Summary of responses
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Direct from slaughterhouse: 63%
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From transfer facility: 8%
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From both: 29%
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Yes: 62%
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No: 38%
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Yes: 54%
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No: 46%
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Immediately: 25%
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Within 1 hour: 50%
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When transport becomes available: 25%
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Left in covered trailer until removed from site.
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Materials would be loaded back into vehicle delivering and sent off-site.
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Rejected material not stored on site, it is not unloaded from the carrier.
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Any material to be rejected is pumped to lorry in an enclosed area.
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The material is stored in containers that are covered and sealed.
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Yes: 20%
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No: 60%
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Investigated/dealt with on a case by case basis: 20%
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Yes: 75%
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No: 25%
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Yes: 35%
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No: 65%
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No outside storage after 30 minutes: 33%
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Up to 4 vehicles allowed for 20 minutes: 33%
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2 vehicles may be parked for up to 8 hours: 33%
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Yes: 48%
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No: 52%
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Blood delivered directly into a specified tank.
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Fallen stock, blood and all other raw material are handled separately.
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Fallen stock that need samples removed from their brains or hides/pelts
removed prior to being rendered are allowed to be tipped on the floor.
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Offal and blood pumped from tanks; feathers in a wet system.
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Implementation of BAT – raw material management
• Effective management of the raw material supply chain will involve:
– Liaising with raw material supplier(s) to ensure that materials arrive on site as soon
as possible.
– Setting acceptance criteria for raw material received at the site, especially the odours
associated with raw materials, as well as specifying effective and leak-proof
enclosures/covers, and implementing a procedure to check and reject nonconforming deliveries.
– Setting a maximum period from production to delivery at rendering plant.
– Having a contingency for rejecting unacceptable raw material
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Implementation of BAT – raw materials - case studies
• Technical material supported by a case study on “Management of odour from
fallen stock”
• Fallen stock is often in an advanced state of decay when they arrive on site.
• The case study shows the benefit of:
– Procedures for managing odour during raw material reception and handling and
maintaining the procedures to minimise the emission of any nuisance odour in relation to
the handling of raw materials.
– Engaging and incentivising local farming communities as this can reducing delays in
receipt of fallen stock to the rendering plant, resulting in the delivery of lower odour and
higher value raw materials.
– Providing suitable management systems, with a range of odour control systems, can be
used to provide abatement of odours from fallen stock receipt and storage. Using an
appropriate odour control system delivers adequate abatement without incurring
additional costs which would result from more extensive treatment of less odorous air
streams, or mixed high/low odour air streams
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Implementation of BAT – Containment
• To minimise the release of fugitive emissions it is
necessary to ensure that as much of the rendering
process is carried out within a sealed containment
envelope. However, simply enclosing sources of
emission is generally not sufficient to ensure that
offensive emissions are prevented. It is also important to
consider ventilation/extraction of air, and treatment of
odorous air streams.
• The rate of ventilation required for effective containment
of offensive odour released within a building depends
mainly on how airtight the structure is.
• Deficiencies in the integrity of the structure and other
openings such as doors, gaps around pipe work, gaps
between cladding sheet etc. allow air to pass into and
out of the building. The larger the gaps in the structure
the greater the rate of flow of air through the building and
as a consequence the greater will be the rate of extract
ventilation required to contain any offensive odour.
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Implementation of BAT – Containment
• The natural forces, which give rise to the movement of air
through a building, are the result of wind passing through
the building and temperature effects created within the
building.
• Local extraction ventilation, can be applied to segregated
air streams containing different levels of odour. The use of
targeted ventilation prevents highly odorous air from plant
and equipment from leaking into the building space and
avoids unnecessarily contamination of the building air. This
reduces the odour strength of any fugitive emission and
has a beneficial effect on building air treatment
requirements. Additionally, applying odour control to a
small volume of concentrated air is more cost effective than
treating a large more diluted odorous air stream.
The overall objective of the ventilation system is to ensure
negative pressure is maintained
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Implementation of BAT – containment
• Summary of industry practice
Aspect
Summary of responses
Is there an airlock serving the raw
material area?
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Yes: 39%
No: 61%
How are the buildings enclosing the
raw materials and processing area
fabricated?
How is the negative pressure within
the buildings designed?
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single skinned: 71%
double skinned, with insulation: 19%
double skinned, without insulation: 10%
Set using air changes per hour (ACPH) : 86%
Monitoring negative pressure: 14%
Additional material provided
Where variable ACPH rates are applied:
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1.9 ACPH when there is one cooker operational (based on flow to biofilter). However, as
some addition extraction is applied directly to plant and equipment and is fed to the
thermal oxidiser (TO), the total ACPH may be slightly higher.
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ACPH by area: Raw Material Room 4; Dryer Room 9; Press Room 22.
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ACPH by area: RM Reception 2.6; Effluent Treatment Room 1.3; Filter Room 28.5; Meal
Lorry Loading Area 11.5; Meal Grinding & Sterilising 6.1; Process Area 4.8; Area above
Cooker 25.1; Crushing Area 7.2.
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ACPH by area: Raw Materials Building 10; Process Building 10; Meal Building 5.
Where fixed ACPH rates are applied:
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Rates applied range from 2 to 10 ACHP
Where negative pressure is monitored:
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Monitoring negative pressure: 9 to -11 Pa; negative pressure monitoring is used to adjust
extraction rates.
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Implementation of BAT – containment
• Summary of industry practice
Aspect
Is raw material deposited into a lidded
hopper which allows air to be extracted
directly from the raw material storage?
What equipment is fully enclosed and
extracted directly to an odour-control
system?
Other plant which is enclosed and
extracted to an odour-control system
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Summary of responses
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Yes: 21%
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No: 79%
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Cooker: 94%
Steriliser (where used): 84%
Presses/centrifuge: 83%
Meat and bone meal (MBM) coolers/grinder: 58%
Raw material bins, blood/waste water/tallow tanks.
MBM handling system.
Decanters/buffer tanks/bins.
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Implementation of BAT – containment - case study 1
• Technical material supported by a case study on “Building integrity and maintenance”
• The case study relates to an operator who has a policy of dealing with odour control
issues before they become problematic, and sees the whole of the site operation as
contributory to the control of odours. Consequently, a pro-active approach is also
incorporated into the site’s on-going maintenance regimes.
• The case study shows the benefit of:
– An experienced site management team to identify the importance of building integrity
and build this into the design and maintenance of the rendering plant.
– Controlling of air leakage from the building to enable a satisfactory negative pressure
regime to be maintained.
– Implement a regular building fabric inspection and maintenance programme to
ensure that building integrity is maintained.
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Implementation of BAT – containment - case study 2
• Technical material supported by a case study on
“Building integrity and air extraction”
• This case study describes the use of monitoring
techniques to verify building integrity and
pressure differentials at an animal rendering
facility.
• The case study shows that
– Building integrity testing is an important component of an
on-going maintenance programme to ensure that the
escape of fugitive odours is minimised. Appropriate inhouse procedures should be documented and all results
recorded and maintained for inspections.
Air
lock
Cooking Room
Thermal oxidiser
Storage
Material intake
Meat outloading
Poultry processing
– Smoke tests and pressure differential tests provide useful
tools for operators in ensuring a high standard of control of
fugitive odours. Ideally, the operator should identify key
locations within the process building where the pressure
drops can be monitored regularly across a series of
pressure transducers.
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Implementation of BAT – containment - case study 3
• Technical material supported by a case study on
“Continuous monitoring of negative pressure”
• The operator has located a series of pressure
transducers at key locations to monitor the
pressure drop across the fabric of different parts
of the process buildings.
• The case study
– Demonstrates the benefit of negative pressure testing
which provides a useful tool to demonstrate on a
continuous basis whether fugitive emissions are likely to
have occurred or are currently occurring /on-going.
– Shows that the magnitude of outward air flow (positive
pressure), monitoring should be carried out using a
pressure transducer capable of reading positive and
negative pressures. [see plots]
– Shows that placement of the pressure monitors
(transducers) is also important; typically, one monitoring
device is installed per area. They should not be placed
adjacent to building openings (doors or air intakes), as this
may result in false readings.
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Implementation of BAT - active odour control – risk
assessment
Sources of odour
• The main cooking process (highintensity process vapour/odour
sources);
• The downstream processing of the
cooked material (greaves) to separate
fat from meal (high-intensity foul-odour
sources); and
• Building ventilation air (low-intensity
odour sources).
The report presents information on
abatement of high and low intensity
odour
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Implementation of BAT - active odour control – risk
assessment
Lays out key questions required to determine whether
BAT is being applied:
• Does the operator know what the odour-control plant
must achieve to avoid complaints?
• Is the capacity of the control plant installed (or
proposed) adequate for the application?
• Is the technology appropriate and reliable for dealing
with the nature of the odour stream to which it is
applied?
• How reliable is the technique?
• What measures must be taken to ensure that the
odour control plant is controlled and operated
appropriately?
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Implementation of BAT - active odour control -– risk
assessment
Summary of impact assessment approaches used by operators
Aspect
How was (were) the height of the
stack(s) serving the main odour control
plant determined?
Is there a stack serving the odour
control plant which treats the air
extracted from the buildings or back-up
system?
How was the height of this stack
originally determined?
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Summary of responses

Manufacturer recommendation: 3%

Using HMIP D1 calculation: 16%

Using air dispersion modelling of air pollutants such as nitrogen dioxide: 34%

Using air dispersion modelling of residual odour: 25%

Not known / Other: 22%
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Yes: 63%
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No: 37%
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Manufacturer recommendation: 8%
Using HMIP D1 calculation: 12%
Using air dispersion modelling of air pollutants such as nitrogen dioxide: 24%
Using air dispersion modelling of residual odour: 36%
Not known / Other: 20%
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Implementation of BAT - risk assessment case study
• Technical material supported by a case study on “Advanced modelling techniques
in complex urban settings ”
• Dispersion modelling is a well established tool, however there are limitation in the
way models deal with certain situations (e.g. complex building situations).
• The case study showed that CFD
– can be an additional, and very powerful and useful, tool to assist with investigating odour issues and
designing solutions.
– is limited in the range of weather conditions that can be represented.
– Still requires good information on odour emissions
– Modelling is expensive
Neighbouring
industrial
building
(a)
stack
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Lower
Transportation
interchange station
(b)
stack
Higher
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Implementation of BAT – odour control – process fume
• For control of intense odour from the
process, the report considers the use:
– Boilers – treating odour as part of
combustion support air.
– Recuperative thermal oxidisers – using
back end boilers to recover heat
– Regenerative thermal oxidisers – using
canisters to transfer heat to incoming
odour
• The report provides a brief summary of the
operating principle of each technique
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Implementation of BAT – odour control – process fume
• Summary of current practice
Aspect
Summary of responses
How are the fumes from the
30% use condensation + oxidation in boiler.
cookers/processors and presses/centrifuges
94% use a purpose-built oxidiser.
treated?
6% use a non-thermal control technique. This represents one small site employing a biofilter.
What type of purpose-built thermal oxidiser 73% have a recuperative TO (i.e. the plant has a back end boiler to recover heat as steam).
(TO) is used?
23% have a regenerative TO (i.e. the plant has a heat exchange system to utilise heat to warm incoming air).
What is the target residence time and
8% have operating criteria of 0.81 second 850oC
combustion temperature used in the TO?
15% have operating criteria of 1 second 850oC
15% have operating criteria of 2 second 850oC
If oxidation is carried out in the steamraising boiler, what is the minimum rate of
boiler firing?
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62% have operating criteria of 2 second 950oC
Range of values from medium (ca. 30%) to high fire (ca. 70%)
© Ricardo-AEA Ltd
Implementation of BAT – odour control – process fume
• Example performance data – use of steam raising boilers
Category
ABP processed
Cat 3
Slaughterhouse and butchery waste 120,000
Inlet (ouE/m3)
Outlet (ouE/m3)
Odour
reduction (%)
90%
70%
55%
15%
1,420,000
2,390,000
2,982,000
1,601,000
5,700
22,500
19,800
9,100
99.6%
99.1%
99.3%
99.4%
15%
2,771,000
418,000
84.9%
<40%
826,400
11,200
98.6%
Plant throughput Firing rate
(tpa*)
Cat 1-3
Fat, bone, offal, knacker, blood, 155,000
poultry, food waste, feathers and
fallen stock
various
20%
1,667,725
3,389,706
5,639
6,922
99.7%
99.8%
Cat 1-3
Fat, bone, offal, knacker, blood, 150,000
poultry, food waste, feathers and
fallen stock
Not recorded
38,820,000#
26,950
99.93%##
6,700
99.98%
29,500
99.94%##
6,850
99.99%
48,435,000#
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Implementation of BAT – odour control – process fume
The report list factors which influences the
performance of oxidation using boilers for example:
• Poorer odour abatement performance can be
expected from a system where the process
demand for steam is lower than the total capacity
of the boiler – capacity of the boiler is important
• If the boiler-firing rate varies greatly, it may be
necessary to operate auxiliary burners in the
boiler to maintain the temperatures necessary for
oxidisation of the odorous substances – periods
of no or low fire are likely to be a problem
• The flow rate of the organic-contaminated stream
must not overwhelm the gas-handling capability
of the boiler induced-draught fans. May be a
problem at low firing rates
The report provides guidance on what could give
rise to problems. This is also provided as “do’s” and
“don’ts” to reiterate good and bad practice.
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Implementation of BAT – odour control – process fume
Similar data and guidance is also presented for recuperative and regenerative
thermal oxidisers:
• Example performance data
• Factors influencing performance:
– Combustion conditions
– Odour loading
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Implementation of BAT –process fume –case study
• Technical material supported by a case study on “Thermal oxidiser capacity”
• The case study compares the performance of recuperative thermal oxidation
by two operators with different design philosophies:
• The case study identified the following problem area with the first operator
– Poor maintenance of residence time
– There was no monitoring of process vapour flows to the TO
– The frequent plant breakdowns;
– Poor quality of workmanship on the backend boiler lead to odour emission
• The case study showed the need for
– Robust data on vapour throughput and energy balance for calculating the TO
capacity requirement.
– Adequacy of residence time, temperature and mixing must be demonstrated
– Adequate monitoring for example during sudden changes in the mass emission of
odour to the thermal oxidiser.
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Implementation of BAT – odour control – building air
• Summary of current practice
Aspect
How is the air extracted from raw-materials
reception and the process building treated?
Where a biofilter is used, is it covered, and is
the treated air discharged through a stack?
Where a biofilter is used, is the media
replaced at defined intervals?
Where a biofilter is used, have there been
problems with the management of the
media (e.g. drying out, compacting)?
Summary of responses
Biofilter using wood chip: 44%
Biofilter using other media: 11%
Chemical scrubber – single stage/scrubbing medium: 7%
Chemical scrubber – multiple stage, single scrubbing medium: 4%
Chemical scrubber – multiple single stages/scrubbing media: 11%
Carbon filter: 4%
Thermal oxidiser: 15%
No treatment: 4%
Yes: 22%
No: 88%
Yes: 67%
No: 33%
Yes: 38%
No: 62%
Odour removal efficiency data as well as do’s and don’t’s on non-combustion types of odour control systems are
in the report
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Implementation of BAT – odour control – abnormal
emissions
• During instances of oxidiser or boiler malfunction, the primary odour control plant
may not be able to destroy odour effectively, leading to an abnormal operating
condition.
• The operator must ensure that procedures are in place to ensure compliance with
the odour boundary condition.
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Implementation of BAT – odour control – abnormal
emissions
• Summary of current practice
Aspect
How are the fumes from the
cookers/processors and
presses/centrifuges treated when the
main combustion plant is unavailable?
How quickly does the back-up system
become fully operational?
How often is the back-up used?
How often is the operation of back-up
checked?
Has the performance of the backup
system been tested using olfactometry?
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Summary of responses
Back-up incinerator: 5%
Condenser only: 5%
Condenser + boiler:– 30%
Condenser + boiler then chemical scrubber (only used until part
processed material is complete): 5%
Condenser + chemical scrubber: 15 %
Condenser + biofilter:– 30%
All inlet and outlet valves closed to contain odours:.5%
No treatment: 5%
Instantly: 50%
Within 3 minutes: 15%
Not specified: 35%
Every time the system shuts down: 55%
Once a week: 5%
Once a month: 5%
Less than once a month: 5%
Never: 5%
not specified: 25%
Every time the system shuts down: 24%
Once a day: 6%
Once a week: 18%
Once a month: 12%
Never: 12%
not specified:29%
Yes: 47%
No: 53%
© Ricardo-AEA Ltd
Implementation of BAT – odour control – abnormal
emissions
Options available include diverting process
air to :
• A second thermal system
• A biofilter or chemical scrubber
• Another dedicated back-up system e.g.
acid scrubber + carbon filter
The report contains limited data on the
performance of back-up systems.
The report recommends that monitoring is in
place to show when the back-up system is
used.
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Sample point
Non condensable flow
Outlet (ouE/s)
3,900,000
Post acid scrubber
1,800,000
Post condenser
1,200
© Ricardo-AEA Ltd
Implementation of BAT – inspection & maintenance
• For the effective operation of an animal by-product rendering plant, it is not just
sufficient to use appropriate plant and equipment. Routine inspection by the
operator will ensure that the plant and equipment is, where necessary, maintained to
ensure the impact of odour from the plant is minimised.
• For key plant and equipment, planned maintenance by the operator is essential.
This will comprise preventive maintenance (changing parts and routinely checking
the function of equipment), in which the maintenance event is pre-planned and all
future maintenance is pre-programmed. The operator should create a maintenance
schedule for every key item or plant according to operating experience or
manufacturer’s recommendation. The maintenance interval may be set based on
equipment running hours or based on environmental risk.
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Compliance monitoring - overview
Compliance monitoring for a rendering plant is focused on demonstrating that:
• The process does not cause significant pollution (specifically, offensive odour) beyond
the boundary of the installation, as required by an odour boundary condition.
• The process is operated in accordance with BAT - as defined by the conditions of the
permit  for both normal and abnormal operation, when some aspect of the plant fails.
The report provides:
• An overview of odour monitoring techniques to assess compliance with permit
conditions.
• An overview of operator and regulatory compliance monitoring with respect to the
application of, and general compliance with, BAT for the minimisation or elimination of
odorous emissions from rendering plants.
• An overview of site inspection procedures.
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Compliance monitoring – industry practice
Summary of current monitoring practice
51
Aspect
Are odour measurements carried out on the odour-control
system treating process/foul air?
Summary of responses
Yes: 76%
No: 24%
What techniques are used?
Olfactometry: 38%
Chemical: 19%
Both olfactometry and chemical: 19%
Other (not specified) : 24%
Are odour measurements carried out on the odour-control
system treating building extraction air?
Yes: 67%
No: 33%
What techniques are used?
Olfactometry: 29%
Chemical: 29%
Both olfactometry and chemical: 21%
Sniff test: 7%
Other (not specified) : 14%
Are olfactometry tests required by conditions of a permit?
Yes: 33%
No: 67%
Has odour modelling been carried out?
Yes: 71%
No: 29%
Are measurements carried out during peak production?
Yes: 53%
No: 47%
Have measurements been carried out during abnormal
operation?
Yes : 24%
No: 76%
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Compliance monitoring – techniques covered
• The report seeks to draw on established monitoring and assessment methods
published elsewhere:
Guidance document
SG8
Techniques for odour monitoring
Sniff test
Odour diaries
Olfactometry
Chemical quantification
Operator self-monitoring
Monitoring of process parameters
Techniques for compliance monitoring
Atmospheric dispersion modelling
Regulatory compliance visits
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Irish EPA AG5
(EPA, undated)
H4 (Environment
Agency, 2011)
(Northern Ireland
Environment
Agency, 2012)
SEPA Odour
guidance (SEPA,
2010)
Odour
guidance for
Local
Authorities
(Defra,
2010)
Section3
Section 4
Section 2.4
Section 2.4
Section 2.5
Section 5.4
Section 5.5
Section 5.6
Section 5.7
Section 5.1
Section 5.8
Section 3
Section 1.6.3
Section 1.6.2
Section 1.6.1
Section 4.4
Section 4.5
App 3
App 6
Section 1.6.2
Section 4.2
App 3
© Ricardo-AEA Ltd
Compliance monitoring – techniques covered
The report summarises the principles behind a range of monitoring approaches that you
may have come across:
• Use of diaries and other data gathering methods to assist in identifying the existence,
cause and extent of an odour problem.
• Sniff tests, as this relates to the test included in a typical odour boundary condition, may
be applied by regulators and operators.
• Testing for odour using surrogate chemical measurements (e.g. hydrogen sulphide and
other reduced sulphur compounds, ammonia and amines).
• Olfactometric analysis in accordance with European Standard EN ISO 13725:2003: “Air
quality. Determination of odour concentration by dynamic olfactometry”.
• The use of dispersion modelling to substantiate and develop odour measurements and
survey reports.
As with other aspects of the report it provides “do’s and don’t” on each technique and
considers the level of uncertainty associated with each technique.
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Compliance monitoring – process monitoring
Invariably odour emissions from the rendering process will be caused by parameters
within the process or the control system deviating from the ideal or normal situation.
The deviation from the normal situation may only occur for a short period, but this may be
sufficient for an offensive odour to be released beyond the boundary of the site.
Good process monitoring focused on the correct parameters may show the root cause of
such an emission.
Examples of the type of periodic process monitoring that may be applied are:
• Raw material delivery and inspection;
• Signs of potential blockage/damage/leakage of surfaces/sumps/interceptors/drains;
• Integrity of buildings (only those parts that can be accessed);
• Internal and external housekeeping activities;
• Maintenance/repairs/replacement carried out on critical plant;
• Depressurisation of batch cookers/sterilisers
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Compliance monitoring – process monitoring
Examples of the type of continuous process monitoring that may be applied are:
Odour control plant
Boiler (when used for odour control)
Thermal oxidisers
Chemical scrubber
Biofilter
Condenser
Extraction system
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Parameter
Exit temperature
Excess oxygen
Steam demand of the process
Exit temperature
Excess oxygen
Carbon monoxide
Steam demand of the process
pH
Redox
Temperature
Pressure
Inlet and outlet temperature
Negative pressure
Fan operation (e.g. volume flow rate)
© Ricardo-AEA Ltd
Compliance monitoring – site auditing
Site inspections provide a means of critically assessing current performance of a facility
against BAT.
The report suggests that there are three basic types of inspection:
• Routine inspections - the report describes that as a walk around inspection in order
to carry out a thorough visual check upon compliance with licence conditions and
ensure that no pollution is likely to be caused. There may a targeted focus to the
inspection (e.g. completeness of records, complaints investigation)
• Incident response – may be carried out in response to complaints. The objective is to
identify potential breaches of conditions or pollution at a rendering facility.
• Full site audit – these are usually more detailed site inspections providing a
comprehensive review of the site’s compliance with some or all of its permit conditions
(and, in the case of noncompliance, an investigation into the reasons for the
noncompliance). An audit may also include a thorough assessment of the site’s
operations against its operation procedures.
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Implementation of BAT – site auditing
• An example site inspection carried out is provided and includes:
– Reference to a series of smoke tests which were observed
– A general check of records, logs, procedures etc.
– The findings of a general site work over
No
1
time
13:20
photos
1a
2
13:36
2z
3
13:40
3a
4
5
6
7
13:50
14:05
14:15
14:25
4a
5a
6a
7a
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location
Meal shed: very low wind speed. Lots of orange smoke seen along western eaves (side
adjacent to backyard), eastern eaves obscured, and lots of smoke also seen at southern side
Meal lorry loading area: lots of orange smoke seen along western eaves (side adjacent to
backyard)
Filter house/ tallow filter room: lots of orange smoke from western eaves (not from adjacent
pipe as white smoke/steam undiluted with orange) and possibly from roof ridge.
DAF plant: no smoke observed.
Boiler house (NB boiler off): orange smoke observed from eastern corner
Press area – no smoke observed
Lots of orange smoke observed exiting through roof of CG tower around the cladding inside
the parapet wall and through roof hatches.
© Ricardo-AEA Ltd
Implementation of BAT – site auditing
• The objective for the management of odour is to ensure that there is continual
improvement – the odour situation will be better this year that last year.
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Management of odour
The report compares and contrasts various techniques for the management of odour:
• Management through the application of SG8/ Irish BAT guidance via the permit
• Management through a site specific Odour Management Plan
• Management through a third party audited Environmental Management System
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Management of odour
Permit
realisation
route
SG8 & Irish
guidance
Activity-specific
Continuous
improvement
element
Reflects
current
activity BAT
Third-party
accredited
EN Standard
No
Yes
No
No
BAT Yes
Advantages – can define permit conditions based on BAT statements. Provides sector-wide definition of BAT.
Disadvantages – no element of continuous improvement specific for odour management. Review period driven by
permit updates (4 yearly) and BREF review, sector-wide consultation on changes.
OMP
Yes
Yes
Yes
No
No
Advantages - allows dynamic development of odour management in response to changes in process/experience. More
operator involvement in deciding management of process perhaps than in SG8-defined conditions.
Disadvantages - Not definitively part of BAT but could be argued to be part of EMS. A poor or unsupported OMP will not
aid management of installation impacts or regulatory burden.
EMS
No
Yes
Yes
Yes
Yes
Advantages - allows dynamic development of odour management in response to changes in process/experience. May
have more operator involvement in deciding management of process than in SG8-defined conditions. External
accreditation may allow move to ‘light touch’ supervision.
Disadvantages - EMS may be too generic to allow rigorous management of odour. Odour control may effectively pass
partly to EMS auditors, who are unlikely to have expertise or resources to focus on odour management.
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Management of odour
In relation to the management of odour the report concludes:
• To be effective, an OMP needs to be endorsed and operated by all levels of the
installation management. The OMP needs to be a structured management tool that
identifies and sets out control measures for all the operations that have the potential to
release odour. It must also include mechanisms to review and address issues and
ensure improvement and development of the OMP.
• Each of the three options considered in the report has benefits and draw backs.
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Management of odour – practical guidance
The report provides practical guidance on the areas of plant operation and management
that should be considered:
• Source identification and characterisation
• Critical path identification/definition
• Monitoring of critical parameters
• Control measures
• Site-specific odour evaluation
• Odour monitoring
• Communication
• Site management and training
• Review
The report provides an example OMP.
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Management of odour – case studies
The report is re-enforced by reference to a series of case studies:
• Case study 1 – Odour management philosophy
– Viewed as an integral part of the animal rendering process, not as a separate activity.
– Awareness of philosophy reinforced via regular training and updates.
• Case study 2 – Odour risk evaluation
– Need to detail all potential sources/conditions which give rise to odour
• Case study 3  Data recording
– Highlights benefit of recording details of process parameter in a usable format
• Case study 4 - Site liaison committee
– Highlighting benefit of open relationship with stakeholder
– Operator need to be seen to deliver on promises
• Case study 5 - Dealing with complaints
– Highlights benefit of attention to detail when designing odour control plant
– Illustrates benefit of building good relationships with stakeholder
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Legal cases
The report
• Reviewing recent (1999 – 2011) legal proceedings relating to odour. It draws on
relevant odour cases (both rendering and non-rendering) and provides examples of:
–
–
–
–
Prosecutions for breach of permit conditions;
Public nuisance action;
Planning appeals; and
Ombudsman cases;
• Almost all the cases considered demonstrate the repetitive nature of regulatory
infractions arising from animal rendering operations. This suggests that the regulatory
tools currently available are inadequate. A more targeted risk-based approach, which
utilises a range of direct measures, might be more effective in allowing earlier
intervention and avoiding cumbersome criminal processes.
• Operators who breach odour regulations have often breached a range of other
regulations. In many cases, it is the larger rendering businesses which are responsible
for repeat offences, unlike in other sectors. Regulators should be aware of factors such
as regulatory history of the site, the operator’s record of compliance and any non-odour
regulatory failings of the operator’s business.
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Legal cases - examples
Site
Type
Dundas Brothers Limited
Various prosecutions for Numerous breaches of permit between Pleaded guilty
1999-2002- relating to raw material
breach of permit
processing, spills, building maintenance
and the standard of odour control
equipment
Fines imposed [£23K]
Cluttons Agricultural
Various prosecutions for 
breach of permit (2000)
and ABP Licence (2007)

Fines imposed [ £175K]
Milka v Chetwynd Animal
By-Products Ltd
Private nuisance
Sacone Environmental
Limited
[Glasgow & Brechin]
Fairfield Piggeries / RJ
Compton & Sons
Various prosecutions
Various cases relating to
between 1999 and 2009 state/performance of odour control plant,
raw materials management
Planning appeal relating Refused to issue permit on the basis that
to permit application
the operator would be unable to comply
with permit conditions
Private nuisance
Whether a site operating under a EPR
permit can be subject to private nuisance
Barr v Biffa
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Issue
Decision
exceeded permitted throughput,
Pleaded guilty
poor record keeping, making false
statements
Poor raw material management
leading to decomposing material on
site
Poor site operation and odour
management
Outcome
Permit revoked/site closed
[later reopened by another
operator]
Found in favour of the
claimants
Compensation awarded
Found guilty in all
cases
Fines imposed [ £30K]
Appeal dismissed
Found for the
claimants
A site operating under a EPR
licence can still be subject to a
private nuisance action
© Ricardo-AEA Ltd
Legal cases - examples
Site
Type
Issue
Decision
Outcome
Ulster Farm By-Products
Various prosecutions
relating to water quality
and odour from 2002 on
wards
Breach of ammonia limits and failure to
use BAT for odour control; also issues
relating to storage and handling of
materials; and maintenance
Pleaded guilty
Fines imposed [£105K]
Ombudsman case
Failures relating to the regulation of the
site
A degree of
maladministration
found
Appeal allowed
John Clarke Farms, Bury St
Edmonds
Moy Park
John Knights
66
Planning appeal relating Refused to issue permit on the basis of
to permit application
historic complaints and adequacy of
controls
Prosecution relating of Poor practices including shed doors being
odour from poultry
left open, litter (bedding) capped and
rearing
visibly damp underneath, badly
maintained hard standing and no method
of segregating rainwater from dirty water
Appeal to vary permit
Seeking permission to reduce boiler firing
rate limit
Prosecution relating of Various permit breaches
breach of permit 200811
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Pleaded guilty
Fine and costs imposed (£42K)
Appeal dismissed
Pleaded guilty to
permit breaches, with
breaches of OBC left
on file
Fine and costs imposed (£150K)
© Ricardo-AEA Ltd
Legal cases - examples
Legal material supported by a case study on “permit
revocation”
• The case study describes the way the Irish EPA
handle a persistently bad operator and highlighted
the following problem areas
– management and permit compliance leading to
serious odour
– siting of plant
– relationship with stakeholder
– Inability to upgrade OCS to control odour
• The case study showed
– the need for Careful siting of plant
– the need for Increased regulatory action may be
required on some sites
– That the regulatory process can be long and drawn
out
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Legal cases - conclusions
Example cases show they are generally decided on the basic failures in management
and/or operating practices, rather than on breaches (or potential breach) of an OBC.
• Thus to mount a successful actions it is clear that the regulator must have a good
understanding of the process Almost all of the cases above demonstrate the repetitive nature of regulatory
infractions arising from animal rendering operations. This suggests that the regulatory
tools currently available are inadequate, assuming that the goal of regulation is not
merely to punish infractions but also to anticipate them and avoid their occurrence.
• Overcome by instilling a philosophy of self-regulation by means of improving
management of odour??
Operators that breach odour regulations have often breached a range of other
regulations, both environmental (e.g. water, air) and non-environmental (e.g. health
and safety, competition).
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Conclusion
We hope that
• The report as a whole provides additional material, which taken alongside the existing
statutory guidance will aid you in improving the management and control of odour at
rendering facilities.
• The information contained in the report shows that rendering plants can be operated so
that their impact on the local community is minimal. In order to achieve this it is
necessary to treat odour management as a principal function of the process activity
rather than as a supplementary issue.
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Dr Nigel Gibson
Ricardo-AEA Ltd
The Gemini Building
Fermi Avenue
Harwell, Didcot,
OX11 0QR
T: 01235 75 3609
E: nigel.gibson@ricardo-aea.com
W: www.ricardo-aea.com
www.ricardo-aea.com
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