MYTH # 1 Efficient Combustion Technologies can increase efficiency and reduce emissions.
Supercritical Pulverised Coal Combustion (PCC) - uses high pressures
and temperatures. This can increase the thermal efficiency of the plant
from 35% to 45%. This reduces emissions as less coal is used.
Fluidised Bed Coal Combustion (FBC) - allows coal combustion at relatively low
temperatures, which reduces NOX formation. A sorbent is used to absorb sulphur.
Coal gasification - coal is reacted with steam and air or oxygen under
high temperatures and pressures to form syngas (mostly carbon monoxide
and hydrogen). Syngas can be burnt to produce electricity or processed
to produce fuels such as diesel oil.
The world standard for efficiency at a power plant using pulverised
fuel technology, the most common technique, stands at
37.5%. Advanced pulverized fuel technology increases the
average efficiency to just 41-44 percent with a forecast improvement to
50 percent in the next 100 years. Other clean coal combustion
technologies are still in early stages of development and are unlikely
to improve efficiency beyond 43%.
MYTH # 2 : Coal washing lowers the level of sulphur and minerals in the coal.
Coal washing results in the formation of large quantities of slurry.
This is placed in waste piles. Rain drains through the piles, picking
up pollutants which end up in rivers and streams. This runoff is acidic
and contains heavy metals.
MYTH # 3 During combustion,
“clean coal” technologies utilize pollution controls for existing power
plants to reduce emissions of pollutants.
Particulate emissions – can be reduced by Electrostatic Precipitators
(ESPs) and fabric filters. ESPs are most widely used. Flue gases
are passed between collecting plates. These attract particles using an
NOX emissions – can be reduced by Low-NOX Burners (LNB). These reduce
the formation of NOX by controlling the flame temperature and the
chemical environment in which the coal combusts. Selective
Catalytic or Non-Catalytic Reduction (SCR/SNCR) are expensive and less
SO2 emissions - can be reduced by Flue Gas Desulpurisation (FGD). Wet
FGD, or wet scrubbing, is most common and absorbs SO2 using a sulphur
absorbing chemical (sorbent), such as lime.
Trace elements emissions – these include mercury, cadmium and arsenic.
Some emissions can be reduced by particulate controls, fluidised bed
combustion and FGD equipment. Activated Carbon Injection is being
trialled to remove mercury.
Between 7 and 30 percent of coal consists of non-combustible material
that just has to be eventually disposed of. “Clean coal” technologies
attempt to trap these waste products before they leave the smokestalks;
waste material that is trapped is then used (despite containing a
number of toxic elements) or dumped as landfill.
The use of higher quality coal – lower in ash and sulphur should reduce
emissions and increase efficiency, but thermal efficiency is increased
by only one percent. If clean coal is used to meet the increased
electricity demand predicitions of govenments instead of cleaner
renewable alternatives, there will in fact be a net increase in carbon
According to a report by the United Nations Environment Programme
(UNEP) mercury and its compounds are highly toxic and pose a ‘global
environmental threat to humans and wildlife.’ Exposure to
it has been associated with serious neurological and developmental
damage to humans. The report also states that coal-fired power
and heat production is the largest single source of atmospheric mercury
emissions. According to the Coal Utilization Research Council
‘there are no commercial technologies available for mercury capture at
coal-fuelled power plants’. Furthermore, a US Department of
Energy commissioned report, states that the consistent, long-term
performance of mercury control has yet to be
demonstrated. Experimental removal of mercury is prohibitively expensive at
$761,000/kg mercury removed and even then 10% of the mercury still remains.
MYTH # 4 Carbon capture and
storage (CCS) can trap C02 from fossil fuel combustion and “storing” it
in the sea or beneath the surface of the earth.
CCS is cost intensive. It increases the costs of power generation by 40
to 80% compared with conventional power plants, depending on the
location of the plant and the storage site, and the transport and
capture technology used.
CCS produces additional long-term costs. Monitoring and verification
over decades is necessary to guarantee the retention of the stored
carbon dioxide. Even then, opportunities to intervene in order to
prevent or control unexpected leakage events are likely to be limited.
CCS is not a technology of today nor of the immediate future because of
technical uncertainties as to whether it will work or not.
Focusing on renewables is still the best way to go.
A Risky Business
Despite $5.2 billion of investment in the US alone , clean coal
research has been plagued with difficulties. For example, of the 13
clean coal projects that the US General Accounting Office looked at,
eight had serious delays or financial problems – six were behind
schedule by 2-7 years and two were bankrupt and will not be completed.
The operators of the $297 million Healy Clean Coal project in the USA
intend to retrofit the current clean coal plant with traditional
technologies. The plant has been closed since January 2000 because
safe, reliable and economical operation was not possible with the
Hidden Social and Environmental Costs
Social and environmental problems caused by the use of coal begin at
the point where coal is mined. Mine workers are at great risk of
death, injury and illness. Local communities suffer from land
degradation and pollution and in many cases are forced to relocate.
At a coal-fired power plant, coal is pulverised and burnt in a high
temperature furnace. Various toxic gases and tiny particles are
released from the furnace into the smokestalks; pollution devices are
used to try to trap pollutants before they are released into the
atmosphere. The use and disposal of solid wastes trapped in the
furnace and the release of gases and fine particles from the
smokestacks have severe impacts on terrestrial and aquatic ecosystems
and people's health.