FOR DISCUSSION
Butcher’s Pet Care Limited re Coton Park, near Rugby.
Comment on Second Response from AEA to ADAS
Supplementary Report of September 2007
Issued by Ian Barrie, Head of Met Office Rural Environment Team
& Steve Peirson, Principal Odour Consultant
Submitted to:
Butcher’s Petcare Limited
15 October 2007
Prepared by:
Steve Peirson
ADAS
Hollyshaw House
Hollyshaw Lane
Whitkirk
LEEDS
LS15 7BD
TEL: 01964 551317
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Ian Barrie
Met Office Rural Environment
Team
ADAS
Woodthorne
Wergs Road
Wolverhampton
WV6 8TQ
TEL: 01902 693245
1. Introduction
ADAS carried out dispersion modelling, and prepared a report of the findings, to
evaluate the odour impact of a proposed new factory for Butchers Pet Care at
Coton Park. This work was set out in a report dated February 2007 and will be
referred to as the ADAS February Report.
Further modelling and interpretation from ADAS was included in a response by
Butchers to questions raised by the local authority in July 2007 (Response to
Planning and Environmental Health Queries on Air Quality raised in e-mail dated
22nd June 2007). This work will be referred to as the Butchers June Response.
These submissions were subject to an independent appraisal by Dr Nigel Gibson
of AEA Energy & Environment on behalf of the Coton Park residents Association.
Dr Gibson’s appraisal was provided to Butchers and ADAS on 29 August and
ADAS was then commissioned by Butcher’s Petcare Limited (BPL) to conduct a
supplementary odour impact assessment to address some matters raised by
AEA. This supplementary report was prepared in early September and will be
referred to as the ADAS September Response.
AEA has now made a further response, to the ADAS September Response behalf
of the Coton Park Residents Association. This response was set out in a letter
from Dr Gibson dated 20 September 2007. The commentary set out below
provides a response to the points discussed in Dr Gibson’s letter.
2. Commentary
2.1.
Paragraph 10 of PPS23
Dr Gibson highlights planning guidance from PPS23 to the effect that “The
planning system should focus on acceptable use of land, rather than control of
processes or emissions themselves. Planning authorities should work on the
assumption that the relevant pollution control regime will be properly applied and
enforced. They should act to complement but not seek to duplicate it”
In this case the pollution control regime for the proposed development would be
the IPPC regulations, which would be enforced by the Environment Agency and
the proposed plant would not be allowed to operate until an IPPC permit was
issued by the Agency. The issue of such a permit would be conditional on
Butchers demonstrating, to the Environment Agency’s satisfaction, that adequate
odour and other pollution controls are in place.
2.2.
Emission Rate Data
Summer to Winter Variations - Any possible variations in odour emissions
from raw materials will be minimal because all raw materials would be, as
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they are at the Company’s current plant, chilled or frozen at the site of
origin and delivered to the proposed plant in temperature controlled
vehicles. The same chilling/cooling, refrigerated transport and storage
arrangements will be used throughout the year.
“Enforcement” of Proposed Emission Limits – The mechanisms for
regulating odour emissions at source are set out in some detail in the
Environment Agency’s H4 draft guidance on Odour at IPPC regulated
installations. This guidance clearly provides acknowledgement that such
limits are a practicable means of regulation. Routine emission sampling
and olfactometric analysis, at for example 6 or 12 monthly intervals,
provides a means to demonstrate compliance. A requirement for such
routine testing may well form the basis of a planning condition.
Emission limits have been successfully incorporated in regulatory
requirements on IPPC permitted sites elsewhere, such as at the Mersey
Valley Sludge Processing Plant (Shell Green).
As Dr Gibson points out, the guidance at paragraph 10 of PPS23 makes it
clear that the Environment Agency would be responsible for the control of
pollution and emissions from the proposed plant. The Agency is a
competent and experienced regulatory body, and as far as ADAS are
aware, it has not raised any objections to this proposed regulatory
approach in their responses as a statutory consultee. The matter of any
possible seasonal variation in emissions could be readily addressed in
permit conditions relating to the time of year when routine and/or regulatory
sampling and emission limit testing would have to be carried out.
2.3 Effective Stack Height
This point concerns the effect of stack diameter at the point of plume release, and
Dr Gibson had previously pointed out an anomaly in the ADAS modelling which
concerned a reduction in the proposed rate of air/odour extraction from the
factory.
In simple terms the modelling outlined in the main ADAS February Report was
based on Butcher’s best prediction, at that time, of air extraction from the factory
with emissions modelled as discharged to atmosphere through a stack with a
terminal diameter of 1.75m.
By June 2007 Butchers had received a more detailed proposal for ventilation and
extraction from the plant from Messrs Dust-EXtraction, as set out in Appendix 1 to
Butchers June Response. This proposal was based on more effective enclosure
of the steaming process line so that lower rates of extraction could be used (as
was later advocated by Dr Gibson in his commentary on the earlier ADAS
reports). The Dust-Ex proposals reduced total extraction rates, and this in turn
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meant that the terminal diameter of the stack could be reduced to 1.3m to
maintain a beneficially high discharge velocity of 18 m/s.
The point that Dr Gibson quite correctly raised in his review of the ADAS
supplementary report was that the stack diameter had not been adjusted down by
ADAS to 1.3 m in model Run 9. The effect of not making this adjustment in stack
diameter would be a slight exaggeration of the dispersion effect in this model
runs. ADAS expects that the lower plume inertia effect of this omission would be
largely, if not entirely, offset by additional thermal buoyancy from the adjacent the
hot boiler plume which is discharged from the same stack.
However, further modelling was undertaken, along with other “worst” case factors,
to fully address the issue of the reduced stack diameter in early September. The
results of this modelling with the correctly adjusted stack diameter (1.3m) were
presented in model runs 14, 16 & 17 in the ADAS September Response. These
later model runs still do not take any account of the beneficial additional
heat/buoyancy effect of the boiler emissions on the dispersion of odour plumes,
so they effectively represent a worse than worst case scenario in terms of
effective stack height.
2.4 Reduced Weekend Emissions
Dr Gibson quite rightly points out that the lower rates of ventilation at weekends
will reduce odour plume momentum and dispersion. However this effect would
not offset the significant reduction in overall odour emissions at weekend caused
by the fact that there would be no “production” odour emissions. Dispersed
weekend odours, with the lower stack momentum were modelled in Run 15, and
peak off-site impact concentrations at 1.5m are a factor of two to three lower (at
ground level) than the already low levels predicted for weekdays.
The effects of ambient temperature on weekend emission rates will be
insignificant. Firstly, because of the proposal to use refrigeration plant to control
temperature in the “waste” room of the plant, and secondly because the Company
would, as they do now, remove waste trailers from the site at the end every
production week.
2.5 Odour Impact at Higher Levels
The 5m and 10m receptor height dispersion modelling carried out by ADAS to
address previous concerns expressed by AEA showed no breaches of the most
testing H4 odour impact criteria (98th percentile1.5 ouE/m3). Practically, it is
inconceivable that any goods or products in neighbouring warehouses and
factories could be tainted by odours that would in any case not be strong enough
to cause any annoyance or loss of amenity.
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2.5 Impact Criteria
As Dr Gibson pointed out, there would be a range of odours from the proposed
development, with the likelihood that the most offensive odours would arise from
the waste and effluent facilities, while less offensive odours would arise from the
meat steaming/cooking operations. Despite the fact that the less offensive
steaming or “cooking” odours will predominate, ADAS has adopted precautionary
approach by adopting the “most offensive” impact criterion of 1.5 ouE/m3
suggested in the draft H4 guidance.
ADAS has included 0.5 ouE/m3 odour contours in mapping impacts for many other
sites simply as a means of adding useful information about the nature and extent
of dispersion characteristics. ADAS has not advocated the use of such a
standard as an impact criterion in any application. The H4 guidelines are widely
acknowledged to provide a very high level of protection without any adjustment.
In fact some industry sectors, such as the wastewater industry, have always
maintained that the H4 guidelines apply an overly strict test in comparison with
perceived odours in practice.
It is not clear why Dr Gibson advocates such a massive adjustment (a factor of
three reduction) in impact criterion in this case. He was apparently content to
suggest, and use, an unadjusted “medium” offensiveness standard (3 ou E/m3) in
the case of food factories in London (Kolak and Katsouris). These food factories
had an established complaints history, and heightened receptor sensitivity to
odours, which could well be considered to be verging on most offensive as
residents have reported odour descriptors including “hot vomit” and “like belly
pork gone off”.
2.6 The Precautionary Principle
The accumulated effects of a number of “worst case” factors by ADAS in the
dispersion work, such as an assumption of 24/7 production, the ridged roof
simulation and no account of enhance odour plume buoyancy from the boiler
plume, together with use of the most rigorous 1.5 ouE/m3 impact criterion
demonstrate a precautionary approach.
2.7 Peak to Mean Ratios in Modelled Outputs
The procedures and interpretation that ADAS have used are fully compliant with
the most authoritative regulatory guidance, which is the methodology provided in
the Environment Agency’s H4 Odour guidance.
2.8 BAT Assessment
BAT will be addressed in the IPPC permit application procedures with the
Environment Agency.
However, as pointed out above, and detailed in
submissions in June 2007, Butchers have already received, and in principle
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adopted, proposals from Dust-EXtraction for enhanced enclosure and lower
ventilation rates from production areas. These reductions in ventilation rates
provide the opportunity for significant reduction in electrical energy requirements,
and thereby significantly contribute to the longer-term energy efficiency and
overall sustainability of the plant.
The thin layer steam cooking process is potentially vulnerable to uneven product
temperature treatment if, for example, high air speed were to be inadvertently
generated at the sides of the steaming “belts” by low level hoods and extraction.
The Company currently has a proven steaming process and product consistency
that could be compromised by more radical enclosures and reductions in overall
extraction ventilation.
2.9 High Level Receptors
The concerns raised by AEA about potential high level receptors were fully
addressed by ADAS in the supplementary modelling undertaken and reported as
Runs 16 and 17 in the ADAS September Response. These runs included other
“worst case” factors and there was compliance with the strict 1.5 ou E/m3 impact
criterion which ADAS has consistently applied in this case for all receptors. Had
ADAS used the 3 ouE/m3 impact standard which AEA were happy to use or accept
for commercial premises in the Beckton study, then there would have been an even
greater margin of (perceived) protection.
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