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20 November 2009
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Without doubt, light road vehicles are a major
source of pollution today. These include the pick-ups and 4x4s, so beloved
by Cypriots.
Recent reports have shown that about 60,000
vehicles have not undergone mandatory MoT testing. It can be assumed that
this is not because of the small fee, but because the owners know that they
haven't a chance of passing. Many of them can be seen on the roads, spewing
clouds of smoke from their exhaust pipes. This is certainly increasing local
pollution levels and could be stopped overnight by strong action.
However, this is only a small part of the
problem. There are seven types of polluting emissions coming from cars, even
as they are driven away from the showroom, with an eighth type on cars which
burn petrol containing lead (the sale of which has become very restricted
since May 2004):
-
carbon mono- and di-oxides
-
volatile organic compounds (VOCs)
-
nitrogen oxides (NOxs)
-
heavy hydrocarbons
-
sulfur compounds
-
particulate matter from exhausts
-
particulate matter from friction between
tyres and road surfaces
-
lead compounds.
As a general rule, the larger the car, the
higher is the amount of pollution produced. For this reason, I suggest that,
for passenger use, it is unnecessary to have cars with engines larger than,
say, 2 litres capacity in a country where the speed limit on motorways is
100 km/h and where one can drive from one side of the island to the other in
less than two hours.
In my opinion, only petrol-driven cars with a
catalytic converter should be used for passenger use. It is true that
diesel-engined cars consume less fuel per 100 km than their petrol-driven
counterparts, of equivalent power. However, this is no advantage in terms of
pollution. The amount of carbon in diesel fuel is much higher than in the
more volatile petrol, so that the carbon dioxide produced is substantially
equal (typically 150 - 450 g eq. C/km, depending on engine size and other
factors). All the other of the first six pollutants in the above list are
higher with diesels than with petrol-engined vehicles fitted with a
catalytic converter, even if the diesel burns desulfurised fuel.
That having been said, some of the latest
diesel engines have become less polluting, provided they are correctly
maintained. However, the advantage of this is reduced as the wear on the
engine components increases, typically after having run 75,000 - 100,000 km.
The big advantage of diesel cars used to be the
very considerably lower cost of diesel fuel. However, this advantage has
diminished and is expected to do so even more in the future. In many EU
countries, the cost of diesel fuel is either the same as petrol or even
higher, in attempts to reduce pollution. As diesel engines are larger for a
given power production than petrol ones, under the new car tax regime,
owners of diesel cars with a given performance level will pay more for this,
and insurance, than would their petrol-burning counterparts.
A decade or so ago, 4-WD cars were useful,
because there were many dirt roads in Cyprus. Today, most roads have a hard
surface. The 4-WD therefore has lost its main raison d'être. I
address a question to owners of 4-WD vehicles: when was the last time that
having all-round traction allowed you to get out of a difficulty that would
have been impossible with a conventional passenger car? I wouldn't mind
betting that a large majority of non-agricultural owners, if they were
honest, would answer years ago. Even the forest roads are negotiable with
conventional cars. So, why have this feature which adds heavily to the cost
of a car and adds to the weight and therefore the fuel consumption?
What is a converter? Such a system meters some
air into the exhaust gases before they go into the converter. This is a
container containing thousand of ceramic beads, each coated with a
microscopically thin layer of platinum or a similarly coated ceramic grid.
As the hot exhaust gases hit the platinum, the latter reacts chemically with
them, without being consumed, and this reaction is what is called
exothermic, which means that the temperature rises. In fact, it reaches a
bright red heat and this allows any residual combustible material in the
gases to be burnt. The result is considerably reduced emissions of carbon
monoxide, VOCs, NOxs, heavy hydrocarbons, sulfur compounds, etc.,
all of them pollutants. It should be noted that converters do not reduce
carbon dioxide emissions, another pollutant.
There is one proviso with converters; if leaded
petrol is used, even in minute quantities, the platinum becomes "poisoned".
One tankful of leaded petrol will stop a converter from working, for ever.
It is quite an expensive component to replace, but this cost would have to
be borne by the careless motorist, because the MoT test will reveal the
problem. It is for this reason that the filler tubes of cars with converters
have a diaphragm which will not allow the filling nozzle of a leaded petrol
pump to enter.
Diesel cars cannot be fitted with catalytic
converters and this is one of the reasons why they are more polluting.
However, they can be fitted with a particle filter, which reduces some of
the larger particles.
Let's have a look at the pollutants in the
above list.
Carbon dioxide is the major cause of global
climate change (see the essay on Climate
change). Cyprus has a legal obligation to minimise emissions of carbon
dioxide. Reducing these may involve:
-
improved public transport
-
reducing the use of cars (e.g., walking the
kids to school)
-
using cars with lower fuel consumption
-
using cars which do not need fossil fuel
(e.g., electric, biological fuels)
-
heavy carbon taxes
Carbon monoxide, which is a highly toxic gas
causing semi-chronic cumulative damage to the oxygen-carrying capacity of
the blood, oxidises in the air to carbon dioxide within a day or two,
depending on the abundance of hydroxyl radicals.
VOCs are organic gases or vapours. Typically,
in this context, they are vapours or decomposition products derived from
unburnt or partially burnt fuel. Their effect is essentially local and they
are a component, along with NOxs, of the smog, haze and ozone
that affects most towns, especially in summer. Anyone approaching Nicosia
from the south on a hot summer's afternoon will have seen the pall of
pollution over the city and blocking the view of the Pentadaktylos mountains
to the north. This is largely due to motor traffic. The mechanism is a
chemical reaction between the VOCs and the NOxs, triggered by
sunlight. The resultant reaction is also the precursor of a second
photochemical one, which produces ozone, a highly toxic and irritant gas
when it is at ground level. It requires only trace amounts to cause a
reduction of immune system responses and this is the probable cause of a
number of diseases, including asthma in children.
There are some natural producers of VOCs, such
as terpenes and terpenoids emitted by a few aromatic plant species. The
quantities in cities from these sources are negligible. On the other hand,
in forested areas, natural VOCs may approach similar levels to those
produced by vehicles.
There are several different kinds of nitrogen
oxides. The only normal major natural source is the reaction between the
nitrogen and oxygen due to the heating effect of lightning strikes. Most of
this is immediately washed out by rain. All combustion at temperatures
exceeding about 500°C will produce NOxs and that in the cylinders
of a car engine is no exception. This is the other component, with VOCs,
required to produce smog, haze and ozone, especially in cities (see the
preceding section).
This is a phenomenon normally associated
principally with diesel engines, although it does occur, to a small extent,
in petrol engines, especially if badly maintained. Unburnt fuel, in contact
with the cooled cylinder walls, and oil which passes the piston rings and
valve guides, often undergoes a number of reactions because of the heat and
pressure. These often produce polymers of the alkane groups and other heavy
hydrocarbons, as well as VOCs. Many of these heavy molecules are dangerous
to lung tissue and some may even be carcinogenic (causing cancers). Even if
you cannot see exhaust gases, these heavy hydrocarbons are inevitably
produced. If the exhaust is actually visible, then the problem is severe.
All fossil fuels contain sulfur compounds.
These are mostly removed during refining, especially the specially
desulfurised fuels, but there is always a small proportion remaining. These
produce sulfur dioxide during combustion and this oxidises in the air to
form sulfur trioxide. This combines with humidity to form sulfuric acid, a
major component of "acid rain". This can cause various illnesses in plant
and animal life, including a contribution to emphysema and asthma in humans.
It also causes attack of the surfaces of marble and limestone (e.g., the
problems with the Parthenon in Athens) and, when it does so, it releases
carbon dioxide, increasing the atmospheric loading. It is also believed that
sulfuric acid, resulting from the combustion of fossil fuels, was a major
contributor to the deaths of some 4,000 persons during the smog in London in
December 1952
All vehicles emit particulate matter, such as
tarry soots. These have been identified as probable carcinogens (similar to
those produced by cigarette smoking). With cars fitted with catalytic
converters, most of this particulate matter, with a well maintained engine,
is burnt, except that the converter does not start to work until it becomes
hot, usually after 5 or 6 km after starting from cold. This is also when the
engine runs "rich" (i.e., with a higher fuel-to-air ratio), so that the
combustion is incomplete and most soot is formed. A car with a converter is
just as polluting as one without a converter in these first few kilometres.
Diesel engines tend to produce more particulate matter than petrol engines
and cars, of all types, with a high oil consumption especially so. The
particles can be wind-borne over considerable distances, especially in dry
conditions.
This is an inevitable part of road transport.
We all know that a tyre wears down its tread at a rate of (very roughly) 1
mm/5,000 km, depending on the car, the tyre composition, the way it is
driven and so on. This represents between 150 and 250 g of rubber compounds
per tyre. With 800,000 tyres from private vehicles in Cyprus running 15,000
km/year, on average, it means that about 500 tonnes of rubber compounds are
lost. Most of this is transformed into dust and such dust cannot be healthy,
even if it is inevitable.
At the same time, the road surfaces are worn,
probably to a similar degree. Most of the surfaces are made from compacted
hot melt petroleum bitumen aggregate (usually referred to, incorrectly, as
asphalt). The bitumen is formed from the still bottoms after the refining of
petroleum and consists of an unrefined mixture of many heavy hydrocarbons
and carbon. Almost certainly, some of these hydrocarbons are suspected
carcinogens. The quantity of bitumen converted to dust is unknown.
Tetraethyl lead (TEL) has been added to petrol
to prevent "knocking" in engines since about 1923. This allows the
compression ratio of the engines to be increased, thereby obtaining a better
efficiency without premature ignition and thus damage to the engine.
The quantity of TEL added to petrol was small,
up to 0.8 cm3 per litre, but the total quantities of petrol sold
are enormous, leading to an annual consumption of thousands of tonnes of the
substance. Most of the lead passed through to the exhaust in a variety of
compounds, some as gases, some as dust. Lead compounds are very toxic to
humans and cause a variety of health problems. In particular, the brain and
intellectual development of children is severely retarded when they are
constantly exposed to lead compounds. It has been found that the lead
content in the blood of children has been reduced by more than 75% in
children in the USA since the sale of leaded petrol was banned.
For the anecdote, the man who discovered that
TEL reduced "knocking", Thomas Midgeley, a mechanical engineer with no
knowledge of chemistry, was also the same person who discovered CFCs, used
in refrigerators, causing depletion of the ozone layer; this one man had on
his shoulders the responsibility for two major and potentially dangerous
environmental hazards!
Unfortunately, leaded petrol was still on sale
in Cyprus up to May 2004, even though its bad effects have been known for
over 30 years. This did nothing for anyone and I urge everyone, in the
strongest terms, never to use anything but lead-free fuel. If their car is
old and will not accept it, then the engine should be modified to allow
modern fuels
to be used (or taken off the road!). It was an anomaly that leaded petrol
was still on sale here, when it has been banned for many years in most
developed nations.
Of course, the best way of reducing pollution
from cars is not to use them! The first and foremost way is to use public
transport. Unfortunately, the public transport system in Cyprus is almost
non-existent and is totally unco-ordinated. It is an urgent requirement that
this be addressed so that anyone in any locality can reliably reach any
other locality in, say, half-a-day with no more than two changes. This could
be co-ordinated with mail delivery. The example of the postal buses in some
European countries shows that this can be done with radiating services from
hubs which are interconnected by high-speed coaches (or rail in some other
countries). The crux of the system is that there are always postal buses
waiting for the arrival of each coach, having delivered passengers from the
outlying areas and waiting to take new passengers back there. This would
require very radical planning and infrastructure. The important point is
that it must be made convenient. It could be done.
The idea of a new rail system for the backbone
should not be discounted, either. It would be possible to interconnect
Nicosia, Limassol and Larnaca with 15 - 25 minute travelling times from
city-centre to city-centre, with a spur to Paphos from Limassol. This would
require vision, but it would cost little more than adding a third lane in
each direction to the motorways. Container freight could also be carried
from Limassol port to the other cities, relieving the motorways of their
polluting juggernauts.
Of course, as I mentioned earlier, walking the
kids to school, rather than using the car, as well as light local shopping
would be helpful, especially as cars are at their most polluting on short
trips. Planning the heavy shopping, such as to the large supermarkets, to go
only once every two weeks, requires some forethought. For the daily
perishables, use the nearest shop; even if a salad there costs 35 cents when
the large shop charges only 30 cents, the difference is equivalent to only a
little over a kilometre in a car in one direction, just for the fuel.
A heavy carbon tax on motor fuels is necessary.
This would bring the price of diesel to over that of lead-free petrol, but
it is the only way to discourage people from buying cars with high
consumptions and encourage those with low consumptions. This has been seen
recently in the USA, where small cars and hybrids are now worth their weight
in gold, while SUVs have become literally almost worthless. An initial price of
€ 1.50/litre, rising to €2.50 in five years may be sufficiently
impressive and would pay for the public transport infrastructure. The car tax on
hybrid and super-economical cars is now a nominal €14.00
per year, but could rise to €100,00 for <1.8 litre cars, then to €400.00 for <3
litre vehicles and €1,000.00 for >3 litres, the message should strike home
without disadvantaging the poorer users with small cars.
It would be possible to reduce car-engendered
pollution in Cyprus, including carbon dioxide emissions, very significantly.
This would require a three-pronged approach involving public transport,
low-consumption cars (especially hybrids) and public awareness to allow them
to use their cars more efficiently. More incentives are required to further
these aims and particularly to discourage "gas-guzzlers".
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