feasibility study assessing the impact of biogas digesters ...€¦ · • household air quality...
TRANSCRIPT
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Feasibility study assessing the impact of biogas digesters on
indoor air pollution in households in Uganda
Vianney Tumwesigea, Lauren Harroffb, Andrew
Apsleya, Sean Samplea, Jo Smitha
a University of Aberdeen; bMakerere University
a b
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Vianney Tumwesige,
University of Aberdeen
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Biomass fuel use and poverty
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Environment & Health…
• Humans spend much of their time indoors
• 3 billion people globally exposed to biomass smoke in homes
• Link to pneumonia, lung cancer, chronic lung diseases
• Estimated leads to ~1.2 million premature deaths annually
• In Uganda only 1.3% of rural people have access to modern fuels
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What do we mean by biomass?
Crop residues & dung
Charcoal
Wood
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What are the pollutants in biomass smoke?
• Fine particulate matter (‘smoke’) – PM2.5
– PM10
– Inhalable dust – Respirable dust
• Carbon Monoxide (CO)
• Airborne endotoxin (inflammatory agent)
• Other chemicals (PAHs, Arsenic, Aldeyhdes, Nitric Oxides, Benzene. Sulphur Dioxide)
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What is PM2.5?
• Small particles inhaled into deep areas of the lung
• Epidemiological evidence that PM2.5 air pollution is linked to respiratory and cardiovascular health effects
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A summary of biomass smoke risk…
Relative risk • Acute lower respiratory tract infection children <5y 2.3 (1.9-2.7) • Chronic obstructive pulmonary disease women >30y 3.2 (2.3-4.8) men >30y 1.8 (1.0-3.2) • Lung cancer women >30y 1.9 (1.1-3.5) men >30y 1.5 (1.0-2.5) • Asthma children 5-14y 1.6 (1.0-2.5) >15y 1.2 (1.0-1.5) • Cataracts 1.3 (1.0-1.7) • Tuberculosis >15y 1.5 (1.0-2.4)
- Large increases in risks - Large population exposure (3 billion people globally) - Leads to ~1.2 million premature deaths annually
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Estimated burden of disease for major risk factors
Measures as percentage of total healthy life years lost in the world in 2000
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Air quality targets
…for fine particles PM2.5 - US EPA Air Quality Index
PM2.5 g/m3 AQI Advice
35 Unhealthy for sensitive groups
Heart/lung disease and elderly/ children advised to reduce prolonged exertion
65 Unhealthy Heart/lung disease/elderly/children avoid prolonged exertion; everyone reduce prolonged exertion
150 Very unhealthy Heart/lung disease avoid all physical activity; everyone avoid prolonged exertion
250 Hazardous Heart/lung disease remain indoors; everyone avoid physical activity
…for CO - WHO Air Quality Guidance
6ppm 24-hour mean
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Methods PM2.5 and CO measured before and after installation of digesters in 9 household in Tiribogo, Uganda
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Methods Direct reading instruments used
TSI AM510 Sidepak Lascar CO logger
PM2.5 CO
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PM2.5 and CO levels were measured over 24hours
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Sampling issues
• Sampling equipment problems – Noise – Battery life – Interference
(sources/deliberate) – Cost/security – Modifications of behaviour
• Personal exposures up to 4 times higher than area/static sampling
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Typical household exposure over 24 hours
0
50
100
150
200
250
0
1000
2000
3000
4000
5000
6000
7000
Carb
on M
onox
ide
Conc
entr
atio
n pp
m
PM2.
5Co
ncen
trat
ion
gm-3
Time
PM2.5
Carbon Monoxide
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0
5
10
15
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35
H1 H11 H13 H17 H20 H21 H24 H27 H47
Ave.
CO
Co
nc
(p
pm
)
Households
Average before
Average after
Household exposure to CO (ppm)
Including All Excluding H27 & H13
Mean % Change 24% -25%
Median % Change -27% -33%
EPA limit
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0
200
400
600
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1400
H1 H11 H13 H17 H20 H21 H24 H27 H47
Avera
ge
PM
2.5
Co
nc
(μ
gm
-3)
Households
Pre-installation
PostInstallation
Including All Excluding H13 & H27
Mean % Change 352% -32%
Median % Change -25% -31%
Household exposure to PM2.5
WHO limit
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Conclusions
• Median reduction in PM2.5 and CO are 25%
and 27% respectively
• Household air quality remains outside safe limits for CO (WHO = 6 ppm) and PM2.5 (EPA = 250 g m-3)
• To bring household air quality within safe limits, biogas use should be sufficient to reduce firewood use to less than 10 kg day-1 household-1
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Acknowledgements
Thanks to the Department for International Development (DfID) for supporting this work