LP Gas in Key Applications

The value of switching to LP Gas as an energy source can be demonstrated by examining some
practical applications. Using independent research and practical test data to evaluate and
compare a range of commercially available liquid and gaseous fuels, together with some
“harvested” solid fuels, the health and economic benefits of using LP Gas become self-evident.
The applications discussed include:
• Road transport
• Cooking (focusing principally on developing regions)
• Residential space and water heating
• Electrical power generation
• Other Applications
Annexes to this report provide more in-depth coverage of several topics for readers who may
wish to explore specific technical issues in more detail.
Based on their relative emission rates in each application, each fuel is assessed in relation to its
impact on human health and, where feasible, estimates are made of the consequential economic
impacts of human exposure to each fuel, in each of the applications discussed.
Where it is practical to do so, data is presented graphically, using consistent charting formats. For instance, pollutant emissions relevant to each fuel are displayed on a horizontally oriented bar chart similar to that shown opposite, together with numerical values. Units of measurement are those most appropriate to the application (for instance grams per kilometre for road
transport or grams per megajoule for heating). Pollutant emission rates are based on independent test reports from recognised testing or research organisations. Given the inherent variability of emission test results, even from appliances or vehicles of nominally the same type and technology level, data from multiple tests have been aggregated to generate a representative average value, wherever possible. Where adequate data is available, typical health costs for each pollutant, in the context of each specific application, will also be
displayed in a vertically oriented chart style, for each fuel type (see opposite). Again, health costs are reported in units appropriate to the application. Where it is not feasible to quantify health impacts in monetary terms, the differences are expressed as ratios or as qualitative discussion.
Calculated health costs can vary greatly according to a number of local and regional factors. These include: population density, income levels, health care costs and the extent to which social services are available. (For a more detailed discussion of the health and economic impacts of different pollutants, please refer to Section 4.1. Moreover, pollutant emission rates vary considerably (both in absolute terms and relative to one another) in response to a number of factors, including: the type of appliance, its operating principles, technology levels, the presence or otherwise of post-combustion pollution reduction systems and typical duty cycles. For these reasons, although they have been accounted for wherever it has been feasible to do so, estimates of overall pollutant emissions may not be as precise as those for, say, CO2. For any given fuel CO2 is accurately calculated by simply multiplying the mass of fuel consumed by a single constant number, regardless of the application for which
the fuel is used or the technologies employed.
5.1 Road Transport
Gasoline and diesel have been the principal fuels used in mainstream road transport for over a
century. But concerns over unhealthy air, climate change and dwindling reserves, coupled with
the potential for disruptions to supply, have led to greatly increased availability of alternative,
lower polluting energy sources for motor vehicles. Since the middle of the 20th century, motor vehicle use has been closely associated with public health. This issue was brought to the forefront in California, where a rapidly growing and highly motorised population was subjected to severe photochemical smog episodes caused mainly by emissions of hydrocarbon products and oxides of nitrogen which reacted in the presence of California's strong sunlight. The severe incidence of respiratory and heart related illnesses attributable to the smog, coupled with the loss of visual amenity, led to the introduction of regulated limits for pollutant emissions from new cars and periodic checks on in used cars to ensure that they were being properly maintained.
The rapid increase in popularity of diesel powered vehicles, particularly in Europe and Asia, has
focused a great deal of attention on the adverse health impacts of fine particulate matter (PM),
which is emitted from diesel engines at much higher rates than from gasoline or gaseous fuelled
engines.
The particles generated by internal combustion engines are especially dangerous because of their
extremely small size, with most particles less than one micron (1/1000 mm) diameter. These tiny
particles can penetrate into the deepest and most sensitive parts of the lung, even passing
through the lung tissue directly into the bloodstream. Fine particles have been designated by the
US EPA as a cancer causing pollutant, and are also directly the cause of serious respiratory and
cardiac diseases and possibly brain damage.
For these reasons, the monetary health impact attached to PM is typically around 20 to 30 times
higher per kilogram than for VOCs or NOx, and over 100 times higher than for CO.
Over recent years, controlling PM emissions has been the highest priority for regulators, and the
maximum permitted emission levels have been reduced by a factor of 28 over the past decade or
so. Many new technologies to reduce particle production inside the engine, and to filter particles
out of the exhaust, have been developed to meet these more stringent regulations. NOx
emissions, because of their influence on ozone as well as particles, are also a high priority.
Tables 5.1(a) and (b), below, summarise the progression of European regulation for passenger
cars and heavy-duty trucks and buses since their inception in 1992 (Source:
http://www.dieselnet.com).Over the past half century, every developed country and most developing countries have
progressively introduced similar controls on emission levels from new vehicles. The international
nature of motor vehicle manufacturing and trade has also prompted an increasing level of
harmonisation in emission standards and regulations. The most broadly implemented standards
(generally referred to as the Euro regulations) are those developed through the United Nations
Economic Commission for Europe (UNECE), which are uniformly applied across the whole of the European Union and have also been adopted in many other regions. The European Commission
proposes and adopts first the Euro regulations in the European Union, and then those regulations
are translated into UNECE regulations. The USA still retains its own set of emission regulations,
but work is proceeding to unify the two systems.
LP Gas (often called Autogas when used as an automotive fuel) is the
most widely available and accepted alternative fuel for road transport.
Over 13 million LP Gas fuelled vehicles are now in use around the world,
consuming over 20 million tonnes of fuel annually. As well as being
practical and clean, the attractiveness of LP Gas in many countries is
enhanced through fuel taxation policies which make it a much lower cost
alternative to gasoline or diesel for both light and heavy duty vehicles.
In many instances, LP Gas fuel systems are fitted to vehicles as an
aftermarket conversion, though in some markets, particularly in the
Asian region, factory-built LP Gas vehicles represent a large and growing
proportion of new vehicles.
Heavy-duty LP Gas engines have been in existence for almost 100 years in the USA, but for many
decades their use outside the USA was extremely limited. A number of heavy duty LP Gas engines
(mostly adaptations of their diesel counterparts) are now available from several of the larger
engine manufacturers. These engines are being used in buses and mid-size trucks, mainly in the
USA and South Korea, but increasingly in other regions around the world.
The very low gaseous and particulate emissions from LP Gas engines make them ideally suited for
buses and delivery vehicles operating in urban areas. To address this specific issue in monetary
terms, in 2001 Australia's Bus Industry Council engaged Mr Paul Watkiss, one of Europe’s
foremost experts in transport externality pricing, to translate the outcomes of European
externality studies into an Australian context (BIC, 2001).
Focusing on the pollution damage created by buses, on a cents per kilometre basis, his work takes
account of Australia’s human and vehicle population densities, city size and morbidity/mortality
values, as well as local vehicle emissions performance. The results of his analysis are summarised
in the chart below.

Figure 5.2 is particularly valuable because, even though the work was completed in 2001, it
includes engine and exhaust after treatment technologies which match those required to meet
current regulations (i.e. diesels operating on ultra-low sulphur diesel (ULSD) and fitted with
exhaust particle filters, now more generally referred to as continuously regenerating traps – CRT).
The chart clearly shows how policies which encourage the uptake of LP Gas fuelled buses and
trucks in urban areas have potential to deliver even better outcomes than current diesel
technology, in the areas where it is vitally important to have the cleanest possible vehicles.
The lower emissions from purpose built LP Gas buses have enabled operators to deliver Euro III
and Euro IV emissions performance well ahead of regulatory schedules.
For more detailed information on particle emissions from gasoline, diesel and LP Gas motor
vehicles, please refer to Annex A3 – Particle Emissions from Current Technology Vehicles.
Each of the following four sets of charts and accompanying notes summarises (for different
vehicle categories) emissions of the transport vehicle pollutants which are of most concern from a
health perspective (PM, NOx, HC, CO).
Health cost impacts for individual pollutants use French values calculated by Rabl and Sparado
(Rabl and Spadaro, 2000). The numerical values are in Table 4.4 of this document.
(a)
The two passenger car sets each present data for vehicles operating on gasoline, diesel and LP
Gas. One set relates to pre-2005 cars (Euro 3 compliant) where no particle filter is fitted to the
diesel powered vehicles. The second covers current technology (Euro 5) cars, the diesel versions
of which are almost universally equipped with a diesel particle filter which reduces tailpipe PM
emissions sufficiently to meet the stringent Euro 5 limits.
Passenger Cars
Data for these charts was drawn principally from a comparative emissions project performed
jointly by three independent European emission testing laboratories (EETP, 2004). The data from his project is particularly relevant because it tested the diesel, gasoline and LP Gas variants of
seven different Euro 3 certified cars, enabling direct comparisons to be made of their emissions
performance on each fuel. Looking ahead to future regulations, the program also included testing
of a diesel fuelled variant equipped with a diesel particle filter (DPF).
For the Euro 5 charts, the DPF equipped vehicle results are used for the diesel PM emissions, and
NOx emissions are factored to reflect the lower emissions of this pollutant for current technology
vehicles. Average emissions of the other pollutants were already sufficiently low in the Euro 3
vehicles to meet current Euro 5 limits, so were not factored.
(b) Heavy Duty Trucks and Buses
Although a considerable body of test data exists for heavy-duty vehicle engines, most results are
expressed in grams per kilowatt.-hour (g/kWh), which is not directly convertible to the required
grams per kilometre (g/km) units. Of the available g/km data, many different test cycles have
been used, with different speed profiles and energy content, which make comparisons extremely
difficult.
Fortunately, the Australian Government commissioned a comprehensive series of test programs
over the period 2000-2005, involving transient drive cycle chassis dynamometer testing of almost
900 vehicles, including a number of alternative (CNG and LP Gas) fuelled heavy duty vehicles.
Data from this testing, together with data from other sources, has been distilled into a
comprehensive set of speed-related on-road emission factors (in g/km) by the Queensland State
Government for all regulated pollutants, greenhouse gases and a wide range of “air toxic”
pollutants.
Based on the anticipated increased stringency of progressively introduced Euro regulations, the
data has also been factored to provide emission factors for future years through to Euro 5. Given
the high degree of consistency and coherency in the underlying database, these emission factors
have been used as the basis for heavy duty and bus emission rates.
Only two fuels are included for heavy duty vehicles: Diesel and LP Gas. Gasoline fuelled heavy
vehicles are available, but represent only a tiny proportion of the total population, so have been
omitted. CNG, although not explicitly included, is taken to have similar emission characteristics to
LP Gas for the pollutants under consideration.

PASSENGER CARS AND DERIVATIVES
Euro 3 (no particle filter on diesels)
Diesel vehicles manufactured
prior to 2005 in Europe, and
even today in many countries,
diesel vehicles represent by
far the greatest health hazard
of all fuel types.
This set of charts highlights
the difference in health
impacts of vehicles powered
by diesel, and those powered
by other liquid and gaseous
fuels (principally gasoline
(petrol) and LP Gas).
Diesel, because of its
intrinsically high emission
levels of damaging particulate
matter (PM) and oxides of
nitrogen (NOx) has much
more severe health impacts
than the other commercially
available fuels.
Other regulated pollutants:
volatile organic compounds
(VOCs) and carbon monoxide
(CO) have lower health cost
values. They are inherently
emitted at low levels from
diesels and, since the mid-
1980’s have been tightly
controlled in many sparkignition
vehicles through the
installation of catalytic
converters.
LP Gas has the lowest health
cost impacts of all
commercially available fuels.
Pollutant Emissions (g/km)
Health Cost
(€ per 1000km)
0.035
0.004
0.003
Diesel
Petrol
LPG
g/km
PM
5.6
2.4
0.02 0.00
PM NOx HC CO
Health Cost €/1000km
Diesel
0.6 0.8
0.06 0.02
PM NOx HC CO
Health Cost €/1000km
Petrol
0.5 0.3 0.05 0.02
PM NOx HC CO
Health Cost€/1000km
LP Gas
0.150
0.050
0.020
Diesel
Petrol
LPG
g/km
NOx
0.030
0.090
0.070
Diesel
Petrol
LPG
g/km HC (VOC)
0.240
0.855
1.070
Diesel
Petrol
LPG
g/km
CO
NOTES:
For these older technology engines (which
continue to be installed in new vehicles sold in
many countries), the health cost impacts are
much higher for diesels because of their high
emission rates of particles (PM) and NOx.
8.0
1.5
0.9
Diesel Petrol LP Gas
Health Cost €/1000km
Health Cost
Totals

Application:
PASSENGER CARS AND DERIVATIVES
Euro 5 (with particle filter on diesels)
Until recently, there was a very
distinct difference in the health
impacts of vehicles powered by
diesel, and those powered by
other liquid and gaseous fuels
(principally gasoline (petrol)
and LP Gas).
Diesel, because of its
intrinsically high emission levels
of damaging particulate matter
(PM) and oxides of nitrogen
(NOx) had much more severe
health impacts than the other
commercially available fuels.
Other regulated pollutants:
volatile organic compounds
(VOCs) and carbon monoxide
(CO) have lower health cost
values. They are inherently
emitted at low levels from
diesels and, since the mid-
1980’s have been tightly
controlled in many sparkignition
vehicles through the
installation of catalytic
converters.
However, since 2004 in Europe,
and at later varying times in
some other countries, a high
proportion of new diesel
vehicles have been fitted with
particle filters, which typically
reduce PM emissions by over
90%.
Despite the very significant
health risk reductions for
diesels, LP Gas remains the
cleanest fuel by a wide margin.
Pollutant Emissions (g/km)
Health Cost
(€ per 1000km)
0.0035
0.0040
0.0030
Diesel
Petrol
LPG
g/km
PM
0.6
6.1
0.02 0.00
PM NOx HC CO
Health Cost €/1000km
Diesel
0.6 0.8
0.06 0.02
PM NOx HC CO
Health Cost €/1000km
Petrol
0.5 0.3 0.05 0.02
PM NOx HC CO
NOTES:
For this class of vehicles, overall health impacts are
relatively low for all fuels.
The principal differential is high NOx emissions from
diesels.
6.7
1.5
0.9
Diesel Petrol LP Gas
Health Cost €/1000km
Health Cost
Totals

Application:
HEAVY DUTY TRUCKS & BUSES
Euro 3 (no particle filter on diesels)
This set of charts highlights the
difference in health impacts of
vehicles powered by diesel, and
those powered by gaseous
fuels.
Spark-ignition gas-fuelled
vehicles are starting to be used
more widely in heavy-duty
applications, mainly for urban
buses and delivery trucks, but
are still very much in the
minority.
Gasoline (petrol) fuelled HD
vehicles are rare, though some
continue to be used in the USA
and some developing countries.
Diesel, because of its
intrinsically high emission levels
of damaging particulate matter
(PM) and oxides of nitrogen
(NOx) has much more severe
health impacts than the other
commercially available fuels.
For these vehicles categories,
LP Gas and NG have the lowest
health cost impacts.
Pollutant Emissions (g/km)
Health Cost
(€ per 1000km)
72.0
111.6
0.37 0.04
PM NOx HC CO
Health Cost €/1000km
Diesel
8.6
88.2
1.63 0.03
PM NOx HC CO
Health Cost€/1000km LP Gas
NOTES:
For this class of vehicles, overall health
impacts are significantly higher for diesels due
to high PM and NOx levels.
184.0
98.5
Diesel LP Gas
Health Cost €/1000km
Health Cost
Totals
35
Application:
HEAVY DUTY TRUCKS & BUSES
Euro 4/5 (with particle filter on diesels)
Diesel, because of its
intrinsically high emission
levels of damaging particulate
matter (PM) and oxides of
nitrogen (NOx) had much more
severe health impacts than the
other commercially available
fuels.
However, since 2004 in Europe,
and at later varying times in
some other countries, new
diesel vehicles have been fitted
with particle filters, which
reduce PM emissions by over
90%, in some cases by up to
99%.
Other regulated pollutants:
volatile organic compounds
(VOCs) and carbon monoxide
(CO) have lower health cost
values.
Spark-ignition gas-fuelled
vehicles are starting to be used
more widely in heavy-duty
applications, mainly for urban
buses and delivery trucks, but
are still very much in the
minority.
Gasoline (petrol) fuelled HD
vehicles are rare, though some
continue to be used in the USA
and some developing
countries.
For this group of vehicles, the
new diesel technologies greatly
reduce fuel-specific differences
in health cost impacts.
Pollutant Emissions (g/km)
Health Cost
(€ per 1000km)
NOTES:
The chart opposite highlights the very significant
health benefits flowing from new PM reduction
technologies on modern diesel engines. The health
cost impacts of all fuels are now at similar levels,
It is important to note the health impact of noise are
not monetarized
36
5.2 Cooking
The cooking appliances used by most people in the developed world operate at the flick of a
switch or the twist of a knob. Electricity or a reticulated gas supply provides instant, clean energy
for preparing their food. For hundreds of millions of the world's population, the luxury of choice
does not exist - everything is dictated simply by the need to survive from one day to the next.
The World Health Organisation estimates that more than
half of the world's population rely on dung, wood, crop
waste or coal to meet their most basic energy needs.
Energy from these fuels is thought to account for nearly
one-tenth of all human energy demand today - more than
hydro and nuclear power together. Cooking and heating
with these fuels in confined spaces, often without any flue,
results in exposure to extremely high levels of toxic
pollutants. At times, pollutant concentrations can rise to
levels 100 times higher than the maximum recommended
exposure limits (WHO, 2005-3).
A consequence of this continued exposure, indoor air pollution is estimated to be responsible for
the deaths of more than 1.6 million people every year.
As we have seen in other situations, the most dangerous pollutant is very fine particulate matter
(PM). A large proportion of these particles are less than 1 micron (1/1000 mm) diameter, with
some being even 100 times smaller again. Because of their extremely small size the particles can
be inhaled into the deepest and most sensitive parts of the lung. The smallest can pass through
the lung tissue and directly into the bloodstream, where they can also lead to heart disease and
possibly brain damage.
Respiratory diseases and cancers resulting from exposure to PM are extremely common, and it is
the very young and the elderly who suffer the greatest.
The following chart (Figure 5.3) is indicative of the extremely high incidence of respiratory
problems for women, very young children and the elderly, who often spend most of their time in
the home, in some remote areas in developing nations. The source of pollution causing most of
this illness is smoke from fires used for cooking or other domestic activities.
Figure 5.3: Respiratory Infections by Gender and Age Group – Central Kenya
(Ezzati, 2000)
37
A number of studies have been performed to measure concentrations of particulate matter
adjacent to areas where indoor cooking is performed using a range of fuel sources. Universally,
when the fuel being used is wood, dung, harvest waste or other biomass material, the PM
concentration is many times the WHO recommended exposure limits for humans.
For example, an extensive year 2000 research program (Ezzati M et al 2000) in Kenya measured
indoor PM levels for 14 hours a day over 137 days, in 38 households. The average PM exposure
level was measured to be around 3500 μg per cubic metre during the active learning periods,
rising to 4500 μg per cubic metre when the fires were smouldering. These alarming figures are in
stark contrast to the World Health Organisation's recommended average exposure limit of 20 μg
per cubic metre. The household members were therefore continuously exposed to particle
concentrations 200 times higher than the recommended exposure limit.
A 2005 study (Smith KR 2005) compared the relative amounts of pollution generated cooking a
single meal using a range of six fuels typically available to households in developing countries,
plus biogas. This study also included LP Gas, which was used as the reference against which
emissions from all the other fuels were compared on a ratiometric basis. (See figure 5.4)
1.0
3.1
19
22
60
64
1.0
4.2
17
18
32
115
1.0
1.3
26
30
124
63
1.0 10.0 100.0 1000.0
LP Gas
Kerosene
Wood
Roots
Crop Residues
Dung
Relative Pollutant Levels
PM
VOC
CO
Figure 5.4: Pollutants Emitted Per Meal Relative to LP Gas
The WHO has produced an assessment of a range of risk factors and their contribution to disease.
Indoor air pollution was identified as the eighth most important risk factor and is estimated to be
responsible for 2.7% of the total global burden of disease. This finding ranks indoor air pollution
as exceeding outdoor air pollution by a factor of five, measured by combining the estimated years
of life lost due to disability and premature death.
Note Logarithmic Scale
38
In developing countries with high mortality rates, the ranking increases to an estimated 3.7% of
the total impact of disease, making it the highest cause of premature death after malnutrition,
unsafe sex and lack of safe water and sanitation.
For many people, especially in rural areas, the choices of fuel for cooking are either solid fuel or LP
Gas. As we have seen under the previous two headings, solid fuel is neither an environmentally
sound nor a healthy option and its use should be discouraged. In some countries and Germany is
an example, emissions from domestic solid fuel appliances are monitored and sanctions can be
applied if they are found to have excessive levels of emissions.
But for around half of the world's population the penalties are much greater than a simple fine.
In many poorer countries, cooking over an open fire using wood, charcoal, crop waste or even
animal dung is the only option available. Exposure to the extremely high levels of pollutants
emitted by these fires, particularly in a confined space, is reliably reported by the World Health
Organisation and other independent researchers to result in premature deaths of more than 1.5
million people every year. Women and young children are those most greatly affected.
Providing these families with access to simple LP Gas burners to replace the wood burning
fireplace can dramatically reduce exposure to these harmful pollutants and the tragic
consequences. There are other social benefits. It is often the role of one of the female members
of these families to gather the wood required for the days cooking. This duty, which can involve
several hours of hard work a day, can be replaced by more meaningful tasks.
5.3 Residential Space and Water Heating
5.3.1 Indoor Air Quality
Air pollution is generally associated with the air outside, but under many circumstances higher
levels of pollution can exist indoors. Moreover, since most people spend most (typically around
90 per cent) of their time indoors at home, school or work rather than outdoors, the exposure
time is generally much longer, increasing the risk of adverse health outcomes.
If ventilation of rooms is poor, or if heating appliances and associated flues or chimneys are faulty,
the concentration of some pollutants can build up to levels which may be harmful to human
health. But it should be noted that heaters are not the only cause of high indoor pollutant
concentrations –- other sources can include chemicals in paints, adhesives and furnishing
materials.
Symptoms can range from being quite mild, such as headaches,
tiredness or lethargy; or more severe such as aggravation of
asthma or allergic responses. All indoor combustion appliances,
regardless of the fuel used, need to have an adequate supply of
air to ensure proper combustion and to avoid any build-up of
fumes in the room. Although unflued gas heaters emit
extremely low levels of undesirable substances, compared with
wood and other solid fuels, they too must have adequate fresh
air ventilation to ensure proper operation.
The most significant emissions associated with unflued gas
heaters are nitrogen dioxide (NO2) and carbon monoxide (CO).
Both pollutants are odourless and hence difficult to detect, but CO is of particular concern, since
exposure to high levels can have serious consequences. To avoid risks associated with exposure
to excessive CO levels, most LP Gas heaters are equipped with an oxygen depletion sensor which
automatically turns off the heater if there is insufficient ventilation to sustain complete
combustion.
39
In good condition and properly used, unflued gas heaters only release small amounts of these
pollutants, which have not been found to affect human health. But levels can build up with
insufficient ventilation or if the heater is faulty, or inappropriately installed.
In contrast, solid fuel heaters produce very high levels of respirable particles which, as we have
seen in previous sections of this document can cause ill health or, in extreme cases, death.
Although solid fuel heaters in developed countries invariably have a chimney or flue to carry the
combustion products outside, leakage through cracked or faulty flues, or the occurrence of
chimney “back-draughts” can lead to persistent high levels of particles inside the building.
Open fires, in particular, also require good ventilation to maintain efficient combustion and to
generate sufficiently high chimney flows for effectively entraining the smoke and other
combustion products. As well as producing high levels of carbon monoxide (CO) and fine
particulate matter (PM), solid fuel coal fires also generate a range of acidic sulphur oxides (SOx).
Kerosene heaters emit much lower levels of particle emissions than solid fuel, but the same
precautions regarding adequate ventilation must be observed to avoid excessive CO levels.
Unvented kerosene heaters may also generate acid aerosols (US EPA 1993).
The large number of variables influencing indoor air pollution levels for any given fuel (ventilation
rate, burner design, heat output, flue efficiency, etc) and the disparity between test methods
make it difficult to assemble reliable data to compare pollutant exposure levels associated with a
range of available fuels.
But it is possible to infer potential impacts by comparing the total pollutant emissions from the
combustion of different fuels. Data from the European Environmental Agency (EEA, 2007) allows
such a comparison to be made. Because this data impacts primarily on outdoor air quality, the
tabulated emissions data is located in Section 5.3.2 – Impacts on Outdoor Air.
A number of studies have been performed to explore possible health effects associated with
unflued gas heaters. Most are based on natural gas appliances but, given that the difference in
emissions between these fuels is generally quite small, the results of these studies can also be
applied in relation to LP Gas with a high degree of reliability. Although the results of some studies
show a small effect, others do not, and meta-analyses show no overall effect (Basu and Samet
1999).
In Japan, Shima and Adachi (2000) studied 842 children aged 9–10 years, from 9 elementary
schools and found no statistically significant association between the prevalence of respiratory
symptoms (measured over three consecutive years) and the presence of unflued gas appliances in
the home.
It is therefore reasonable to conclude that, given the general availability of heaters incorporating
automatic safety controls, there is little risk of negative health impacts from the use of LP Gas
heaters, and the use of these appliances certainly minimizes exposure to other hazardous particle
pollutants including sulphur dioxide (SO2) and fine particulate matter (PM).
Even though these findings confirm the low-polluting characteristics of LP Gas heaters for
domestic heating it is worth re-stating that, like all indoor combustion heaters regardless of fuel
type, they must receive adequate ventilation for proper operation.
5.3.2 Outdoor Air Quality.
In many locations solid fuel heaters produce enough pollution to directly affect the health of
people in the community. The impacts are intensified when temperature inversions, commonly
occurring on colder windless evenings, trap the flue gases in layers close to the ground, producing
high concentrations of particles and other unhealthy products of combustion. Visual amenity can
also be degraded significantly by the smoky haze created by these heaters.
40
Research in Australia (Ayers et al 1999) clearly shows that cities where wood burning heaters are
prevalent have much higher ambient particle levels than other cities. For instance, the four major
cities, Sydney, Brisbane, Melbourne and Adelaide yielded average PM10 concentrations in the
range 20-25 μg/m3, whereas Canberra and Launceston (where wood heaters are popular) yielded
averages 2-3 times higher at 43and 65μg/m3 (see Figure 5.5).
0
10
20
30
40
50
60
70
Launceston Canberra Major
Capitals
WHO Limit
65
43
23 25
PM2.5 Concentration (μg/m3)
Influence of Wood Fired Heaters on Ambient PM
Levels in Australian Cities
Figure 5.5: Influence of Wood Fired Heaters on Ambient PM Levels in Australian Cities
Both of the wood-burning cities have low housing density, with relatively fewer industrial and
transport sources, so without the influence of wood heaters it could be expected that particle
levels would actually be lower than the larger cities. The fact that PM levels are significantly
higher underlines the impact on local air quality from wood burning, even in modern developed
cities.
Table 5.6, below, uses data from the European Environmental Agency, published in a 2009 Swiss
report by Atlantic Consulting (Atlantic, 2009) to summarise emission rates in grams per gigajoule
(g/GJ) of energy for both combustion heaters and water boilers operating on gaseous and liquid
fuels, wood and coal/briquettes. This table highlights the very significant benefits of using
gaseous fuels for domestic space and water heating.
Emissions, g/GJ
Fuel NO2 VOC PM10 PM2.5 CO
Residential Combustion Heater
Gaseous 57.0 10.5 0.5 0.5 31.0
Liquid 68.0 15.5 3.7 3.7 46.0
Wood 74.5 925 695 694 5,300
Coal 109 484 404 397 4,602
<50 kW Household Boiler
Gaseous 70.0 10.0 0.5 0.5 30.0
Liquid 70.0 15.0 3.0 3.0 40.0
41
Wood 120.0 400 475 475 4,000
Coal 130.0 300 38 360 4,000
Briquettes 200.0 200 100 100 3,000
Table 5.6: Emissions from Residential Combustion Appliances for Five Fuels (Atlantic, 2009)
Also, from a practical perspective, switching to an LP Gas heater is not only beneficial to the
environment and to community health, but is also much more convenient, more controllable, and
avoids dust and grime build-up in the house interior and areas around chimneys or flues.
5.4 Electrical Power Generation
As well as providing motive power for on road vehicles, internal combustion engines are used in
numerous other applications. The diversity of these applications makes it impractical to cover
them all separately in this report. Additionally, many of the non-road applications utilise only a
very limited range of fuel types. For instance virtually all construction, excavation, mining and
equivalent heavy duty plant and equipment use diesel fuel. Consequently there is an almost
complete lack of data comparing emissions and exposure levels for different fuel types for these
applications.
Nevertheless, some important categories of equipment are available to operate on a range of
different fuels. The most significant of these is local electricity generation, with numerous
examples of generators operating on diesel, gasoline, LP Gas and natural gas. Some other types
of equipment, such as pumps, pressure washers and compressors are also available, to a limited
extent, for operation using several fuel types. All these applications have one important feature
in common, in that they generally operate mostly in constant load, constant speed mode.
Portable and transportable electricity generating plant can therefore be used to characterise
emissions and health impacts associated with this class of equipment. Two types of generator will
be considered in this section; medium power (typically around 100 kW) and low power domestic
or trade type generators, which usually have a rated power less than 15 kW.
42
5.4.1 Medium Capacity Generator Sets
Many rural and isolated communities in both developed and less wealthy developing regions do
not have access to centralised electricity grids as a source of power for lighting, communications
and entertainment.
By necessity electrical power must be produced locally, usually by
way of a diesel powered generator. Unless the generator’s
engine is very modern and equipped with the latest emission
reduction technologies, people living in the vicinity of the
generator plant can be exposed to noise and high levels of
ultrafine particles in the diesel exhaust.
These soot particles, and highly toxic chemicals adhering to the
soot, are linked to the incidence of cancers, are damaging to the
lungs and can also affect the heart and human neurological systems. Compared with a traditional
diesel appliance (not fitted with a particle filter), an LP Gas powered generator will typically have
90 to 98% lower particle emission levels, as well as greatly reducing the potential for exposure to
other toxic substances.
In more developed areas, this class of generator is generally used
either as a standby power source in case of failure of the mains
supply, or as a continuous power source on sites where mains
power is not readily available, such as on construction sites or
where there is a need to drive relatively high powered mobile
equipment.
The example used to illustrate the relative emissions and health
cost impacts for this category of plant is a generator set operating for a continuous 12 hours every
day with a load of 80 kW, powered by a 6.8 litre engine. The fuel types compared are diesel,
natural gas and LP Gas.
Table 5.7 summarises the emission rates of each regulated pollutant in grams per kilowatt-hour,
together with a health cost value (expressed as Euros per tonne of pollutant emitted) for each
pollutant. The health cost values used in the table are representative of mid-level values for road
vehicles operating in a typical developed region. Note: In this example the diesel PM emissions
are quite low relative to the gaseous fuels, probably reflecting the constant load-speed nature of
generator operation, which avoids the very high PM peaks typically observed during acceleration
phases of diesel road vehicles. Conversely, NOx levels are quite high, which is consistent with
continuous high load, high temperature combustion.
Fuel Type
Pollutant Emissions Rates (g/kWh)
HC NOx CO PM
LP Gas 0.14 0.11 4.61 0.03
Natural Gas 0.09 0.62 3.49 0.03
Diesel 0.40 6.43 1.21 0.28
Health Impact Cost (€/kg) 0.7 15.7 0.02 120
Table 5.7: Pollutant Emission Rates for Typical 80kW Generators on Diesel, NG and LP Gas
43
The chart below (Figure 5.8) presents the data in Table 5.7 as a graphic representation of the
relative emission levels (in grams per kilowatt-hour) for each pollutant and fuel type, while
operating at a constant 80 kW load. Emissions data is drawn from the US EPA non-road engine
certification database www.epa.gov/OMS/certdata.htm#largeng
LP Gas
NG
Diesel
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
HC
NOx
CO
PM
0.14 0.11
4.61
0.03
0.09 0.62
3.49
0.03
0.40
6.43
1.21
0.28
Emissions (g/kW-h)
Medium Duty Engine Emissions for Three Fuels
Figure 5.8: Pollutant Emission Rates for Typical 80kW Generators on Diesel, NG and LP Gas
Applying the health cost values in Table 5.7, factored by the annual duty cycle, Figure 5.9 below
illustrates the relative health costs for each pollutant/fuel type combination, together with the
net total health cost for each fuel.
LP Gas
NG
Diesel
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
HC
NOx
CO
PM
34
612
32 1,184
22 3,385
24 1,184
99
35,397
8
11,837
Health Cost (€/yr)
Medium Non-Road Engine Annual Health Costs Based on 80kW
Average Power, 12 hrs/day
TOTALS:
LP Gas........€1,862/yr
NG.............€4,615/yr
Diesel........€47,341/yr
Figure 5.9: Annual Health Impact Costs for Typical 80kW Generators on Diesel, NG and LP Gas
The health impact cost figures clearly indicate the value of using a gaseous fuel, in particular LP
Gas, wherever the choice is available.
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5.4.2 Small Generator Sets
Generators in this category tend to be constructed for intermittent
rather than continuous power generation and are primarily used for
recreation or trade-related activities. In areas where the mains power
may be unreliable, they are also frequently used for domestic power
backup, enabling lighting, refrigeration and other low-power services to
be maintained. Their power output ranges typically from around 15
kW for the larger models, down to less than 1.0 kW for the smallest
examples.
Fuel choices for these appliances are generally gasoline, LP Gas or diesel. Both two-stroke and
four-engines are available, particularly for the gasoline fuelled versions. In many countries the
emissions from small engine-powered equipment is not regulated. This can result in very high
levels of CO, HC and PM being emitted from some engines,
especially if manufactured in one of the countries which currently
do not have domestic emission standards for this type of
equipment.
Taking data from a US EPA report summarising non-road engine
emissions (US EPA 1991) the following table (Table 5.10) compares
emissions of CO, HC, NOx and PM from older generators using
1990’s technology levels, when this type of equipment was not required to comply with any
emission regulations. In the absence of reliable test data from that era comparing like-for-like
gasoline and LP Gas engines, the LP Gas emission figures have been calculated by multiplying the
gasoline emission factor by the ratio of LP Gas/gasoline emissions in Figure 5.7, for each pollutant.
Emissions (g/kW-h)
HC CO NOx PM
2-Stroke Gasoline 279 651 0.39 10.32
4-Stroke Gasoline 12.73 473 2.72 0.07
4-Stroke Diesel 1.74 6.70 8.04 1.34
4-Stroke LP Gas 10.59 473 1.03 0.05
Table 5.10: Pollutant Emission Rates for Unregulated Small Generators on Diesel, Gasoline and LP Gas
Many developed countries have now introduced progressively more stringent regulations for nonroad
engines, but the limits tend to be quite lax compared with those for on-road vehicles. This is
illustrated by the following chart (Figure 5.11), which is directly based on analysis of all relevant
certification test data contained in the US EPA’s 2008 small engine certification database
(http://www.epa.gov/OMS/certdata.htm#smallsi)
45
Figure 5.11: Pollutant Emissions of Small Generators Operating on Gasoline and LP Gas
Using the same pollutant health cost impact values that have been used in earlier sections of this
report, the following chart (Figure 5.12) translates the emission rates into monetary healthrelated
costs, further emphasising the adverse implications of choosing the wrong fuel for this
type of equipment.
Figure 5.12: Health Cost Impacts of Emissions from Small Generators Operating on Gasoline and LP Gas
5.5 Other LP Gas Applications
In every neighbourhood hundreds, if not thousands of engine powered appliances are owned and
used by residents, including lawnmowers, brush cutters, pressure washers, chain saws - the list is
very long. Together, the use of this equipment on a typical workday or week end amounts to a
considerable energy load, with the pollutants spread across the community.
Using the same methodology as that used in the previous section for small generators, once again
the US EPA database has been analysed on a broader front to include all currently certified small
46
spark ignition engines operating on gasoline or LP Gas (dual fuel and mixed fuel engines were
excluded from this analysis).
The following two charts (Figures 5.13 and 5.14) tell the same story as their counterparts in the
previous Section, but in this case are based on analysis of test data for a total of almost 2700
engines in the database.
Figure 5.13: Pollutant Emissions of Small Generators Operating on Gasoline and LP Gas
In this analysis we see similar trends to those for small generators, though, surprisingly, carbon
monoxide emissions from the smallest two-stroke engines (on a grams per kilowatt-hour basis)
are actually lower than for the four stroke group, despite the four strokes being generally
recognised as having much more efficient combustion than the two strokes.
Figure 5.14 provides a perspective on the relative emissions from current model two and fourstroke
small gasoline engines compared with equivalent LP Gas fuelled units.
The health cost analysis follows the same format, though from the cost data we can infer that,
overall, the broader spectrum of equipment in the full database tends to have higher emission
levels than the generator category discussed in the previous Section. Health impact values (in
€/tonne) are the same as those used for motor vehicles and the medium/heavy non-road engine
applications analysed in earlier sections.
47
Figure 5.14: Health Cost Impacts of Emissions from Small Engines Operating on Gasoline and LP Gas
Thermal desiccation (also commonly referred to as “flame weeding”), heats plant tissues rapidly
to rupture cells but not so extensively as to burn them. It is used widely in Western Europe and
the USA to halt the growth of weeds above slow-emerging root crops, such as carrots and
potatoes, as well as for killing weed growth around the stems of some above-ground crops such
as maize.
LP Gas has proved to be an ideal fuel for this application and is now almost universally used,
having supplanted earlier technologies based on kerosene and oil burning. Because it does not
introduce any chemicals into the soil, LP Gas fuelled thermal desiccation completely avoids any
danger of soil contamination, and is widely used for the farming of organic crops.
So we can see there are many wide-ranging applications for LP Gas as a source of heat energy forindustry, the home and for recreation: from metal cutting to grilling a steak to gliding around in a hot air balloon. In all cases, LP Gas provides a convenient, safe, controllable and low polluting
energy source, with minimal adverse impacts on public health