Review of the Potential Impact on Air Quality from Increased Wood Fuelled Biomass Use in London

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Review of the Potential Impact on Air Quality
from Increased Wood Fuelled Biomass Use in London

• Peter Coleman

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Acknowledgements

• Ruth Calderwood from City of London and Jareed
  Boow from London Councils
• Colleagues who did all the work Robert Stewart,
  John Abbott, Alan Leonard, Alan Collings, Pat
  Howes and Nick Barker.

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Great Smog December 1952
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Desired Air Quality
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Scope of London Report

• commissioned by London Councils via the City of
  London
• Drivers for increasing use of biomass
• Legislation and potential controls on biomass
  plant
• Sustainability and transport impacts
• Combustion technologies
• Fuels
• Air quality impacts of renewable scenarios
• A toolkit for the assessment of planning
  applications for biomass heating

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Pollutants Associated with Biomass

• Nitrogen oxides
• Polyaromatic hydrocarbons (PAHs) formed from
  incomplete combustion
• Metals when treated wood is burned As, Cu, Cr(VI)
• Dioxins where waste or treated wood (PCP/
  lindane) is burned
• Particles (PM10 / PM2.5)
• Coarse material entrained chars, fine alkali
  metal salts
• Poor combustion increases coarse particle
  emissions
• Modern plant emissions lower and TSP PM10
  PM2.5
• Abatement therefore difficult

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Pollution Control Regulation for Biomass

• IPPC A(1)
• gt50MW combustion plant burning any fuel
• 3-50MW combustion plant burning fuels containing
  or derived from waste
• gt1te/hour incineration of waste
• LA-PPC A(2)
• Co-incineration of non-hazardous waste associated
  with any A(2) process less than 50MW
• Incineration of non-hazardous waste in an
  incineration plant with a capacity lt1te/h
• Co-incineration of non-hazardous waste in a
  co-incineration plant which is not otherwise an
  A(1) or A(2) process
• LA-PPC Part B
• Installations in which any Part B activity is
  carried out but no A activity including
• 20-50MWth input non-waste wood
• Combustion of fuels containing or derived from
  waste 0.4-3MW exempt from WID
• Incineration of non-hazardous waste in a plant
  exempt from WID but between 50 and 1 te/hour
• Otherwise Clean Air Act 1993

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Modelling Study

• National Biomass Strategy suggested 7 10 of
  energy demand from biomass, perhaps 2 from wood
  fuel combustion
• London Energy Partnership looked at stretch
  targets for carbon reduction by 2026 investigated
  impacts of 5 scenarios of biomass
• Concern at cumulative impact on air quality of
  large numbers of biomass heat/power developments
  in London
• What could the impact on air quality be ?

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Scenarios
Source Units Scenario 1 Scenario 2 Scenario 3 Scenario 4 Scenario 5
CHP MWe 200 200 800 400 500
Large boilers MWth 100 100 500 100 250
Domestic Dwellings 5,000 5,000 50,000 5,000 25,000
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Emission Factors Used
Pollutant Plant Modelled (MWth in) NAEI Factors g/GJnet Clean Air Act Limits g/GJnet Modelling Study g/GJ
Particles 0.022 790 185 76
0.556 37 1040 66
3.33 37 403 40
NOx 0.022 50 - 90
0.556 150 - 150
3.33 150 - 206
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Modelling Assumptions

• No geographic information on where development
  likely.
• Followed LAEI residential and industrial/commercia
  l energy use.
• Wide range of biomass to energy conversion
  technologies available including AD, pyrolysis,
  CHP and other advanced technologies
• Technologies in use by 2026 likely to be
  different from now however the initial wave is
  wood fuelled combustion.
• Assumed all take up by wood fuelled combustion
• Emissions assumed not to be just compliant nor
  best available but typical of modern appliances
  used UNECE Guidebook emission factors
• Date mismatch on background air quality is 2020
  emissions 2026

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PM10 Emissions (te/yr)
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NOx Emissions (te/yr)
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Modelled 2003 PM10
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Modelled PM10 2020 BAU
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Modelled PM10 2020 Scenario 1
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Modelled PM10 2020 Scenario 3
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Key Points from Scenario modelling

• PM10
• BAU below annual and 24 hourly average objectives
  in 2010 and 2020
• Scenario 1 may be difficult to achieve 24 hourly
  objective near busy roads as adds 4 to a
  background of 24 ug/m3
• Scenario 3 both objectives difficult central
  London an. av. of 37 ug/m3
• PM2.5
• BAU below objective in 2010 and 2020
• Scenario 1 may be difficult to achieve near busy
  roads 24 hourly objective as adds 4 on to a
  background of 17 ug/m3
• Scenario 3 widespread breaking of cap
  concentrations approx 30 ug/m3
• Exposure reduction hard to achieve without
  further measures on other sources
• NO2
• BAU exceeds objective in 2010 and 2020
• 3 to 10 ug/m3 increase makes alternative measures
  more necessary
• Uncertainty in the Scenarios
• Potential Impact on Air Quality non-trivial
  what can be done ?

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Measures available to EHOs

• For larger appliances permits
• Smaller appliances Clean Air Act
• Planning permission where required
• Worst case nuisance
• Voluntary agreements on emission quality

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Clean Air Act Powers 1

• Requires all new furnaces other than domestic
  furnaces to be capable of operating smokelessly
  and to be notified to the local authority (s4).
• Allows the Secretary of State to prescribe
  emission limits on grit and dust from furnaces
  other than domestic furnaces (s5).
• Prohibits the use of a furnace other than a
  domestic furnace in a building or outdoors which
  burns pulverised fuel, solid fuel at 45.4 kg/h or
  more or liquid and gas fuels at 366.4 kW or more
  unless it has grit and dust arrestment plant
  fitted which have been agreed by the local
  authority or unless the Local Authority has been
  satisfied that the emissions will not be
  prejudicial to health or a nuisance (s6).
• The limit of 45.4 kg/h for solid wood fuels
  implies _at_ 10MJ/kg 126 kW, _at_ 20 MJ/kg 252kW.
  Hence, pellet appliances would be caught by the
  arrestment plant and chimney heights provisions
  at larger sizes than wood chip or green logs.

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Clean Air Act Powers 2

• Where a furnace is burning pulverised fuel, solid
  fuel at 45.4 kg/h or more of liquid and gas fuels
  at 366.4 kW or more the Local Authority may
  direct that measurements of the dust emissions
  are made (s10). However, if the furnace is
  burning solid matter at less than 1.02 te/h or
  liquid or gas at 8.21 MW or less then the Local
  Authority can be required to carry out the
  measurements (s11).
• Allows the local authority to request the
  occupier of a building to provide such
  information as may be reasonably required on the
  furnaces in the building and the fuels or wastes
  burnt on them (s12).
• Prohibits the use of furnace with a chimney which
  burns pulverised fuel, solid fuel at 45.4 kg/h or
  more or liquid and gas fuels at 366.4 kW or more
  unless the chimney height has been approved by
  the Local Authority following the provision of
  relevant information by the applicant, unless
  application was made and the Local Authority did
  not respond within 8 weeks or a longer time
  mutually agreed (s14, s15).

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Planning

• Where planning permission is required then LAs
  have an opportunity to influence the impact on
  air quality of biomass.
• Air quality is a material planning consideration
  particularly in Air Quality Management Areas (PPS
  23 Pollution Control).
• PPS 22 Renewable energy states Small scale
  renewable energy schemes utilising technologies
  such as .Biomass heating, can be incorporated
  both into new developments and some existing
  buildings. Local planning authorities should
  specifically encourage such schemes through
  positively expressed policies in local
  development documents.
• Planning and air quality can achieve joint
  objectives of sustainability.
• Possible use of S106 agreements under the Town
  and Country Planning Act 1990 to work with
  developers.

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Toolkit

• EHOs approve chimney heights
• 3rd ed Chimney Heights Memorandum not suitable
  for biomass
• Existing LAQM Technical Guidance (LAQM TG(03))
  inappropriate undergoing revision
• Toolkit designed as a simple process to assist in
  the range 50kW to 2MW with chimney height
  determination
• Based on approach used for Technical Guidance
• NOTE uses emission rate so combination of plant
  size and pollutant concentration
• Also provided a tool for LAQM to estimate when
  domestic solid fuel use unlikely to cause
  exceedances for annual mean objective for PM2.5

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24 hour mean PM
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Conclusions 1

• Biomass offers many advantages as a source of
  energy.
• Inappropriate biomass use may impact
  significantly on air quality particularly
  cumulative impacts.
• The impact on air quality of a development is
  influenced by the energy demand, the appliance
  selected, the fuel quality the abatement used and
  the chimney height installed.
• range of emissions especially particles from
  appliances of same output is significant and
  influenced by appliance design and fuel quality.
• Regulation currently does not require high
  quality appliances except through planning
  system.

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Conclusions 2

• A toolkit of approaches has been developed to
  assess the air quality impact of wood combustion
  both plant by plant and cumulatively.
• A fuel certification scheme could greatly reduce
  uncertainty in future plant performance.
• Industry needs clear guidance to enable
  appropriate stalled projects to proceed.
• Industry needs predictability of projects not
  variations between LAs in treatment.
• Significance and cumulative impact need
  addressing.
• Developers and local authorities can achieve
  acceptable gains in sustainability without
  degrading air quality significantly.
• http//www.londoncouncils.gov.uk/biomassresearch

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Possible Future Actions

• Fuel certification scheme for pellet, chip and
  log to reassure purchasers, regulators and supply
  chain - in early stages
• Guidance to developers on chimney heights
  published in appropriate fora to access relevant
  users
• Publication of emission factors so LAs know range
  of performance
• Reminder to specify emission performance in
  planning permission
• Tools to convert between units
• Revision of Chimney Heights Memorandum to provide
  clarity
• Emission Limits for CAA appliance size range fit
  for purpose

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• END

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Scope

• London Biomass Report

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Recent Happenings

• Edinburgh 7 schools biomass project stopped
• Dundee rejected high quality biomass plant as
  will increase air pollution even though no
  exceedences predicted with 5 fold conservative
  modelling and no increase significant at
  receptors.
• Concern about lifetime emissions in absence of
  powers to ensure good operating practice for
  un-permitted plant

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Drivers for Increased Biomass Use

• Issues
• Climate change biomass energy is approaching
  carbon neutrality (excluding limited supply chain
  impacts)
• Sustainable
• Energy security
• Policy Reponses
• EU Biomass Action Plan
• UK Energy White Paper
• Biomass Task Force
• Biomass Strategy
• Merton rule 10-20 of energy demand of
  developments from renewables
• Zero-carbon new homes by 2016

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Air Quality Strategy Environment Act 1995

• PM10
• 50 ug/m3 24h mean not to be exceeded gt35
  times/year
• 40 ug/m3 annual mean
• PM2.5
• lt25 ug/m3 (12.5 Scotland)
• 15 reduction between 2010 and 2020
• NO2
• 200 ug/m3 1h mean not to be exceeded gt18
  times/year
• 40 ug/m3 annual mean
• PAHs
• 0.25 ng BaP /m3 by 2020, EU target 1 ng BaP/m3
  by 2012

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Size Distribution (Erlich et al. 2007)
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Clean Air Act Emission Limits
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Comparison of EU Measurement Methods
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Emission Limits elsewhere
Pollutants Plant Modelled (MWth in) Austria Finland Denmark Sweden
Particles 0.022 111 - 80 207
0.556 111 - 80 59
3.33 37 196 80 59
Nitrogen Oxides 0.022 - - 215 -
0.556 184 - 215 -
3.33 184 - 161 118
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Toolkit

• Anywhere
• Is the appliance permitted?
• Is it a lt16.12kW boiler for domestic purposes
• Is it capable of smokeless operation?
• Burning at gt45.4 kg/h (approx 120 200kW)?
• If so, then agreed abatement equipment must be
  used and
• Chimney height must be determined unless AQ
  impact shown to be so far as practicable not
  prejudicial to health.
• If within a smoke control area then an exempt
  appliance

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Approach

• ADMS used to predict ground level concentrations
  for a unit emission rate from stacks between 10.6
  and 40m and diameters from 0.1-1m
• Stack at centre of 10m cube building
• Discharge temperature 100oC
• Discharge velocity sufficient to overcome
  pressure drop
• Heathrow 2005 metrological data
• 1m roughness
• 1km x1km 10m grid receptors
• 24 model scenarios
• Annual mean, 90th ile 24h mean, 99.8th ile
  hourly mean
• Emission rate for 1 ug/m3 estimated

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Requirements from Developer

• OS grid coordinates of stack
• Height of stack above ground
• Diameter of stack
• Dimensions of buildings within 5 stack heights
• Description of the combustion appliances
• Description of abatement equipment
• Maximum rates of emission of particles and NOx
  (not necessarily at capacity
• If size fractionated PM available use if not all
  PM2.5.

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Annual mean NO2 /PM 1 ug/m3
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99.8th ile hourly NO2 of 40 ug/m3
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Modelled NOx 2020 Scenario 1 Increment
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Modelled NOx 2020 Scenario 3 Increment
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Process PM10

• Calculate a background adjusted emission rate EA
• EA E/(32-G)
• E emission rate G annual average background
  concentration
• If existing concentration gt32 then
• EA E/delta C
• Where delta C is maximum allowed increment
• Use Nomagraph to estimate effective stack height
• If this is lt2.5 times building height or
  buildings closer than 5 stack heights then use
  CHM to calculated corrected stack height
• In all cases
• gt3m above any adjacent area to which there is
  general access,
• gt calculated effective stack height,
• gt any building within 5 stack heights

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Process PM2.5 /NOx

• Calculate a background adjusted emission rate EA
• EA E/(25-G)
• As before
• NOx
• EA E/(40-G) annual mean
• EA E/(200-G) hourly average
• Minimum chimney height is the tallest of the
  three calculated

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Example

• A 500kw wood boiler in a building 30m high by 20m
  square. Stack diameter 0.5m
• Particle emission rate from CAA 0.048 g/s
• NOx from Corinair gives 0.075 g/s

PM10 PM2.5 Annual NO2 Hourly NO2
Emission rate 0.048 0.048 0.075 0.075
Background 25 15 35 35
Adjusted emission rate 0.007 0.005 0.015 0.023
Effective stack height 9.5 3 9 5
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90th ile 24 hour mean PM10 1 ug/m3
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Annual mean NO2 /PM 1 ug/m3
NO2
PM2.5
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99.8th ile hourly NO2
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Example (cont.)

• Critical effective stack height less than 2.5 x
  building height
• From CHM
• Building width B root (202202) 28.3 m
• Lesser of building height (30m) and width K
  28.3 m
• T 30 1.5 x 28.3 72.5m
• T gt corrected stack height so
• Corrected chimney height C 30 9.5 x
  (1-(30/72.5)) 35.6 m
• Required stack height 35.6m (5.6m) if no taller
  buildings within 47.5m of stack

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Screening Assessment for Domestic Biomass

• Seeks to identify maximum density of domestic
  solid fuel use before exceeding PM2.5 objective
• Estimate number of solid fuel using houses in
  500m x 500m square
• Weight houses
• Ceq C 0.36 anthracite 0.56 SSF 0.79 wood
• Estimate proportion of open space L
• Deq Ceq/(1-L)
• If Deq lt D then PM2.5 objective unlikely to be
  exceeded

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Nomograph for Risk of Exceeding for PM2.5
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Validation with 2003 NOx Measurements
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Modelled NOx/NO2 2020 BAU
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Modelled 2003 NOx
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Modelled NOx/NO2 2010 BAU
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Modelled NOx/NO2 2020 Scenario 1
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Modelled PM10 2010 BAU
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Modelled NOx/NO2 2020 Scenario 3
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Modelled PM10 2020 Scenario 1 Increment
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Modelled NOx 2020 Scenario 3 Increment