Otago’s air quality newsletter
June 2009
JOE wON’t gO back tO wOOD
INSIDE
page 2
Why is coal bad?
Learn why ORC is working to
reduce our dependence on
coal.
How does double
glazing work?
Using thermal science to keep
your house warm and dry.
page 3
Lawrence pupils
learn about their air
page 4
Temperature
inversion study
After one winter with his new gas fire, Joe
Forsyth of Alexandra would never go back to
using a wood burner.
Joe found gathering firewood was becoming
a chore and his wood burner was messy,
circulating ash and dust around the house. So
he had a gas fire installed at the beginning
of last winter and received assistance for its
purchase and installation from the Clean Heat
Clean Air Warm Home assistance programme,
run by Otago Regional Council (ORC) and its
partners.
Now the Forsyth family is enjoying the
convenience of their Rinnai Gas Energy Saver
fire, especially the timer which they set for
7am, then off again at 9am when everyone
goes to work, and back on again at 4.30pm.
The house is warm when they get up in the
morning and warm when they get home
from work. They also like the thermostat
for minimum and maximum temperatures,
the quiet, unobtrusive fan, and the lack
of condensation as it vents to the outside.
“It produces plenty of heat and heats our
large living areas – the whole bottom floor
of our two-storey home - and we leave the
lounge door open overnight to heat our
upstairs bedrooms,” Joe said.
Why does Central Otago have
temperature inversions?
Heating options
See which energy source best
suits you.
The cost of gas during the coldest part of
winter was worth it for the fire’s convenience,
effectiveness and having a constantly warm
home without any work. They decided on a
gas fire over a pellet burner or heat pump
because they liked the silence of gas, and
after considering the long-term the rising cost
of electricity.
The Forsyths also received assistance to
insulate their home through the Clean Heat
Clean Air programme. They have concrete
floors but the ceilings were reinsulated with
an extra 150mm of polyester material in
both split level ceiling cavities, making a big
difference to heat retention.
For more information on the Clean Heat
Clean Air programme, phone EnergySmart
on 0800 777 674 or ORC on 0800 474 082.
page 1 - AirZone - June 2009
WHY IS COAL BAD?
Smog is a big problem in some parts of Otago during winter. The
smog caused by burning coal is particularly acrid. Historically coal
has been a massive problem in large industrial countries and cities
overseas where it has been burned in huge quantities.
When smog was stuck over London during the Great London Smog
in 1952, it became hard to breathe and see clearly. More than
4000 people died during this catastrophe, leading to the creation
of clean heat laws with the passage of the Clean Air Acts of 1956
and 1968. The first Act regulated where smokeless fuels had to be
burnt and relocated power stations to rural areas. The second Act
introduced the use of tall chimneys to disperse air pollution from
industries burning coal, liquid or gaseous fuels. Clean air zones
were established and burning coal in these was banned.
There has always been pollution from coal burning in New Zealand
but it has never been comparable to large industrial sites overseas. In
Otago towns such as Milton and Balclutha, it’s convenient for many
people still to burn coal in their fires and multi-fuel burners which
contributes to high PM10 levels in the area. Modern wood burners
emit much lower levels of pollution especially when burning bright
and hot and provide high levels of heat output.
When coal is burned, whether to heat a home, by industry or by a
power station to generate electricity, the gas going up the chimney
contains carbon dioxide, PM10, sulphur oxides nitrous oxides, carbon
monoxide, water vapour, and fly ash to name a few of the major
ingredients.
Sulphuric dioxide is subject to transformative processes in the
atmosphere, which can result in sulphuric acids, sulphites and
sulphates being formed.
Overseas, rain has become acidified from air pollutants including
coal emissions and contains heavy metals including arsenic, lead,
mercury, nickel, vanadium, beryllium, cadmium, barium, chromium,
copper, molybdenum, zinc, selenium and radium, which can
be dangerous at certain levels. While these substances are trace
impurities, if enough coal is burned they can produce harmful
effects on the environment.
Many schools in New Zealand which once used coal fired burners,
are moving away from coal boilers for heating and hot water and
replacing them with electrical or wood pellet boilers.
Dunstan High School and its boarding hostel in Alexandra changed
to a pellet fired system when their air emissions consents came up
for renewal. The school and hostel’s year-round demands for hot
water and heating made them ideal candidates for the new clean
heat system. Tougher emissions regulations meant that the old
coal system had to go, as it was an ongoing source of particulate
pollution in inversion-prone Alexandra. The new boiler gives the
school a level of control and automation that was not possible with
coal, as well as ultra-low particulate emissions.
The Earnslaw steamship in Queenstown is also contributing to
Otago’s clean air campaign. Two combustion fans are being installed
above and below the engine to reduce the carbon emissions from
its engine. The fans will improve airflow around the engine, making
the coal burn more efficiently.
The carbon dioxide and water vapour coal emits also contributes
to greenhouse gases. The combustion of coal adds a significant
amount of carbon dioxide to the atmosphere, more than the
combustion of other fossil fuels. Carbon dioxide emissions from all
forms of coal burning causes pollution by releasing carbon dioxide
molecules into the atmosphere, which react with water molecules
to produce carbonic acid.
Sulphur dioxide from burning coal is one of the most harmful
contaminants for your health, irritating the lining of the nose,
throat and lungs.
Photo right: Earnslaw manager Andrew Husheer shovels coal into the
engine, which is soon to be adapted to emit less carbon
Photo supplied by Southland Times
HOW DOES DOUBLE GLAZING WORK?
There are several methods of keeping your house warm over
winter months, especially in Otago.
Double glazing is one way you can insulate your home and retain
a lot of the heat usually lost through your windows.
All new homes and major extensions built in New Zealand are
required to meet the Government’s new insulation requirements
introduced recently, which includes the use of double glazing.
A single pane of glass provides poor insulation because glass is a
good conductor of heat so much of the heat in your room literally
goes out the window.
Your home’s double glazing operates just like fibreglass insulation
and woollen clothing. It traps a layer of air between two panes.
page 2 - AirZone - June 2009
Air is a poor conductor of heat, so the trapped layer sets up a
blanket of protection between cold air on one side and warm on
the other.
In a home without double glazing, heat goes straight out the
window. Heating (or cooling) bills are reduced in the doubleglazed home.
Low emissivity glass is completely transparent, but provides an
ultimate reduction of heat loss. Sit next to a window in a doubleglazed home and notice the absence of draughts and cold spots.
Condensation is also reduced.
Lawrence pupils learn about their air
Lawrence Area School teacher Bill Lovell-Smith and ORC environmental monitoring officer Lorena Smith instruct pupils how to collect samples from the
town’s air quality monitor
Year 10 pupils from Lawrence Area School are learning valuable
lessons about air pollution since ORC installed an air quality monitor
in the town last year.
Under the guidance of teacher Bill Lovell-Smith, the 13 and 14-yearold pupils are collecting daily samples from the monitor at the
Lawrence bowling club to find out if the town’s air quality exceeds
the National Environmental Standard.
The results of the students’ monitoring will go into ORC’s State of
the Environment air report, due to be released this year, and help
assess if there is an air quality problem in Lawrence, says ORC Air
Quality Scientist Deborah Mills.
“The students are doing a great job changing filters, setting timers
and maintaining the logbooks. This is a screening tool for us and an
educational opportunity for the school,” Deborah says.
Mr Lovell-Smith agrees, saying co-operative projects such as the
one between Lawrence Area School and ORC enrich the curriculum
and make learning meaningful for older students.
They collect samples over 24 hours, one day in three during the
winter from mid-May to the end of September, and every sixth
day the rest of the year. ORC held a workshop last year to teach
the pupils about air quality and how to change filters and run the
sampler.
to have temperature sensors to track the cold air and development
of inversion layers.
The monitoring work by pupils provides cross-curricular learning
opportunities in subjects such as science and maths (e.g.
measurement and statistics); social studies inquiry leading to social
action (e.g. fuel and fire choices, household heating options, old
and at risk people living in Lawrence); health (respiratory disease
and keeping warm); geography (weather, patterns, landscapes and
resources).
Mr Lovell-Smith said what started as a simple mechanical task
for the pupils now also involved social inquiry and action. “The
students feel as if they are part of the whole thing. For example,
they’ve been looking at the impact of diesel vehicles on air quality
as State Highway 8 carries lots of heavy traffic,” he said.
“They have learned the air we breathe is full of different particles
(some filters from a sample day show it can be quite smoggy inside
the inversion layer), they have polished their IT skills (such as using
Excel), looked for patterns in data and attempted to use geographic
ideas to hypothesise connections, relationships and explanations.”
They also collect data from two wireless weather stations, based
at Tuapeka flats and at the school, to observe any connections
between the landscape, weather and PM10 results. They are hoping
page 3 - AirZone - June 2009
The placement of the sensors reasonably replicates the increasing height in the atmosphere.
temperature at Ventry street is colder than that on the hilltop there is a temperature inversion. On
these days the inversion
has at
formed
around sunset
and last until
mid-morning,
a typical
pattern we can see h
By looking
the difference
in temperature
between
sites at different
elevations,
when the sky is clear
in Central
Otago.layer was on any given night and how long it lasted. Figure # Plots
strong
the inversion
temperatures at two different elevations across two days during winter 2008. When
10
temperature at Ventry street is colder than that on the hilltop there is a temperature inversion.
these days the inversion has formed around sunset and last until mid-morning, a typical patt
8
Ventry Street
when the sky is clear in Central Otago.
Hilltop
Temperature inversion study
10
8
Ventry Street
Hilltop
6
Temperature (oC)
Temperature (oC)
Otago Regional Council (ORC) air quality reports often 6make
reference to temperature inversions contributing to increased
4
pollution levels during winter months in Central Otago. An inversion
exists when air temperature increases with increasing height 2above
the Earth’s surface. This often occurs overnight when skies are clear
0
and the surface has cooled significantly, cooling the air directly
above the ground. Since cold air is denser (thus, heavier) than-2warm
air, when an inversion exists the colder air at the surface remains
-4 the
there – along with all of the smoke and pollution. Generally
inversion breaks up in the mid-morning as the sun warms the
-6
ground which, in turn, warms the air at the surface and helps
the
8/07/2008
0:00
atmosphere turn over.
4
2
0
-2
9/07/2008 0:00
10/07/2008 0:00
Date/time
-4
Figureand
#. Average
In order to understand more about this phenomenon
how hourly -6temperature at Ventry Street and on the Hilltop measured on July 8-9
2008.
8/07/2008 0:00
9/07/2008 0:00
10/07/2008 0:00
it relates to air pollution, ORC air quality scientists installed five
Date/time
4-4 shows that when the inversion layer is more intense the day is more likely to
temperature sensors at different points on a hillsideFigure
in Alexandra
experience
high air
pollution
levels.hourly
This istemperature
because anatinversion
layer and
has on
stopped
smokemeasured
and
Figure
#. Average
Ventry Street
the Hilltop
on July 8
at the start of winter. The placement of the sensors
reasonably
Figure 1. Average hourly temperature at Ventry St and on the Hilltop
2008.
replicates the increasing height in the atmosphere.
measured on July 8-9 2008.
By looking at the difference in temperature between sites at Figure 4-4 shows that when the inversion layer is more intense the day is more likely
experience high air pollution levels. This is because an inversion layer has stopped smoke a
Thispollutants
data can
be used
when
looking
at long-term
trendsDays
in with
from moving
upward
from the
surface higher
into the atmosphere.
different elevations, we can see how strong the inversion layer other
inversion layers occur frequently in Alexandra, even when the sky isn’t clear, because of the low
Alexandra.
It
is
difficult
to
comment
on
air
quality
trends
when
they
was on any given night and how long it lasted. Figure 1 plots the lying nature of the basin the town sits in.
temperatures at two different elevations across two days during are so influenced by the weather from one year to the next. But if
This
can the
be used
when
at long-term
in Alexandra.
It is difficult
comment
we data
know
level
oflooking
air pollution
wetrends
would
expect because
oftothe
winter 2008. When the temperature at Ventry St is colder than that on
air quality trends when they are so influenced by the weather from one year to the next. But if
inversion,
and of
weairget
less than
we had
then
can say
know the level
pollution
we would
expectbefore,
because of
the we
inversion,
and that
we get less
on the hilltop there is a temperature inversion. On these days the we
than
we
had
before, then
we
can say that is
thegetting
air pollution
in Alexandra is getting better.
the
air
pollution
in
Alexandra
better.
inversion has formed around sunset and lasts until mid-morning, a
175
typical pattern when the sky is clear in Central Otago.
Figure 2 is a scatterplot of daily average PM10 and the intensity of
the inversion layer during winter 2008 (daily readings 5 June to 31
August).
Heating options
Consumer
recommends
that the two cheapest and
also best means of using
renewable resources for
home heating options are
dry firewood in a modern
woodburner and wood
pellets in a pellet burner.
150
3
Daily average PM10 (ug/m )
Figure 2 shows that when the inversion layer is more intense the day
is more likely to experience high air pollution levels. This is because
an inversion layer has stopped smoke and other pollutants from
moving upward from the surface higher into the atmosphere. Days
with inversion layers occur frequently in Alexandra, even when the
sky isn’t clear, because of the low lying nature of the basin the
town sits in.
125
100
75
50
25
0
-1
0
1
2
3
Figure 2. IntensityIntensity
of inversion
layerlayer
(see (see
notenote
above
forforexplanation)
of inversion
below
explanation)
4
Figure 4-4 Scatterplot of daily average PM10 and the intensity of the inversion layer during
winter 2008 (Daily readings 5 June to 31 August).
Electric heaters are the best
overall choice for people
who rent. Heat pumps
are the cheapest way of
electrically heating your
house.
Reticulated natural gas is still
a good option for those who
have access to it although
connection charges need to
be considered. LPG is more
expensive than reticulated
gas.
page 4 - AirZone - June 2009
Table sourced at www.consumer.org.nz