Unleaded petrol: Safer than leaded?

Unleaded petrol: Safer than leaded?

By Kardono

JAKARTA (JP): Lead gasoline car emission is now widely
debated. It has been linked to health disorders such as
neurological damage and heart disease in adults and learning
disabilities and decreased IQs in children.

The state-owned Pertamina oil company launched unleaded
gasoline in August 1995. It was entitled BTT (Bahan Bakar Tanpa
Timah). The government plans to use this to gradually phase out
lead gasoline.

The World Bank has urged all nations to phase out lead
gasoline because of related health problems.

Studies in the U.S. by Caio Koch-Weser (a World Bank
representative) have suggested that for every dollar invested in
unleaded gasoline a community will save ten dollars in health and
other costs.

The cheapest and most efficient way to make unleaded gasoline
is to add tetra ethyl lead (TEL) to gasoline. This process raises
the price of unleaded gasoline. The market price of normal
gasoline is Rp 700 (US$ 0.3) compared to around US$ 0.4 for
unleaded.

Adding lead alkali anti-knock compounds to gasoline
increases octane quality (RON). RON or research octane number is
an international measure of gasoline quality. A higher number
means higher octane quality - RON numbers for gasoline generally
fall between 80 and 98.

Typically, a car designed to run on 98 RON gasoline will have
a 10 to 15 percent better fuel economy than one designed to run
on 90 RON fuel.

Many older cars cannot use unleaded fuel. Leaded gasoline
lubricates an engine's exhaust valve seats. Older cars have
engines with cast-iron cylinder heads with `soft' valve seats. If
these cars use unleaded fuel, the valves may recess into their
seats which causes engine damage.

Most modern cars are fitted with catalytic converters which
stop this problem occurring.

Fuel additives, made of sodium, potassium and phosphorus,
help older cars use unleaded fuel, but they are not as effective
as leaded fuel, especially when engines are under stress. On the
other hand, unleaded fuel containing these additives cannot be
used in modern catalyst engines.

When reducing or eliminating lead in gasoline, refineries
must add certain components to maintain octane quality. These
components include benzene, toluene, xylenes and ethyl benzene.

Also to enhance octane quality, a refinery is likely to use an
aromatic or oxygenates such as ethers, methanol or ethanol.

These components, added in 5 to 15 percent concentration, are
not cost-effective and may cause technical and environmental
problems.

There is no doubt that high lead levels are dangerous. Lead
can affect the central nervous system and cause hypertension,
increased coronary heart disease, cardiovascular disease and
damage brain development in children. Lead can also cause
deposits in engines and exhaust systems.

Unleaded fuel has been promoted as a replacement to leaded
fuel but there are environmental problems associated with
unleaded fuel which may be more dangerous.

It is well known that aromatic hydrocarbons in gasoline are
carcinogenic, with benzene being the most potent. Increased
exposure to benzene in gasoline is reported to contribute to
increased incidence of leukemia. Unleaded fuel requires greater
use of aromatics.

Increased aromatics also increase ozone levels. The aromatic
and olefinic components of gasoline produce photochemically
reactive exhaust emissions. That is, they will create ozone.

The aromatic, olefins and oxygenates in unleaded gasoline
produce health and environmental dangers greater than lead when
unleaded fuel is used in cars not fitted with catalysts. The
carcinogenic component of such emissions is benzene. Leukemia and
lung cancer are caused by monoaromatic compounds in emissions
including toluene and xylenes, polyaromatic hydrocarbons (PAHs),
formaldehyde and other aldehydes.

Gasoline containing elevated levels of aromatics also have a
higher calorific value. Such fuels have been shown to produce
greater amounts of nitrogen oxides in car emissions.

Good catalysts fitted to well maintained cars are likely to
significantly reduce hazardous emissions. But a question mark
remains over the durability of catalysts, especially three-way
catalysts. We must also see to regular inspection and maintenance
of catalyst-equipped cars.

Three-way catalysts, which control hydrocarbon, CO and NOx
exhaust emissions, necessitates electronic fuel injection, either
multipoint or throttle body, to ensure correct fuel metering.

This is required to maintain an air-fuel ratio which is at or
near a stoichiometric (14.7:1) point so that the catalyst can
simultaneously convert HC, CO and NOx into harmless products.

It is widely recognized that, even in a new car, deposits will
build-up on the inlet valves of fuel injectors and in the
combustion chamber which can lead to more exhaust emissions.

Deposits formed in these sensitive areas are largely due to
olefins and aromatics in fuel which polymerize and decompose into
carbonaceous products.

Clearly, reducing risks from leaded fuel has created other
dangers associated with the increased use of aromatics in
unleaded fuel, especially in non-catalyst and poorly serviced
cars.

Window: Uleadeed fuel has been promoted as a replacement to
leaded fuel but there are environmental problems associated with
unleaded fuel which may be more dangerous.