Coal use & the environment

Producing energy invariably leads to some degree of environmental impact. All sources of energy – fossil fuels, nuclear, renewables – have environmental impacts.

Cooling tower and pylons

The nature of the impact is dependent on the specific generation technology used and may include:

  • Concerns over land and water resource use
  • Pollutant emissions
  • Waste generation
  • Public health and safety concerns

The use of coal for power generation is not exempt from these impacts and has been associated with a number of environmental challenges, primarily associated with air emissions. Coal has demonstrated the ability to meet such challenges in the past and the expectation is that it will successfully meet future environmental challenges.

  • Technologies
  • Resources
  • Coal technology news


Viable, highly effective technologies have been developed to tackle environmental challenges, including the release of pollutants – such as oxides of sulphur (SOx) and nitrogen (NOx) – and particulate and trace elements, such as mercury. More recently, the focus has been on developing and deploying technologies to tackle carbon dioxide (CO2) emissions.

Technologies are now available to improve the environmental performance of coal-fired power stations for a range of pollutants. In many cases a number of technologies are available to mitigate any given environmental impact.

Coal Washing

Mined coal is of variable quality and is frequently associated with mineral and chemical material including clay, sand, sulphur and trace elements. Coal cleaning by washing and beneficiation removes this associated material, prepares the coal to customer specifications and is an important step in reducing emissions from coal use. While coal preparation is standard practice in many countries, greater uptake in developing countries is needed as a low-cost way to improve the environmental performance of coal.


Particulate emissions are finely divided solid and liquid (other than water) substances that are emitted from power stations. A number of technologies have been developed to control particulate emissions and are widely deployed in both developed and developing countries, including:

  • Electrostatic precipitators (ESP) are the most widely used particulate control technology and use an electrical field to create a charge on particles in the flue gas in order to attract them to collecting plates.
  • Fabric filters collect particulates from the flue gas as it passes through the tightly woven fabric of the bag. Both ESP and fabric filters are highly efficient, removing over 99.95% of particulate emissions.
  • Wet scrubbers are used to capture both particulates and SO2 by injecting water droplets into the flue gas to form a wet by-product. The addition of lime to the water helps to increase SO2 removal.
  • Hot gas filtration systems operate at higher temperatures and pressures than conventional particulate removal technologies, eliminating the need for cooling of the gas, making them suitable for modern combined-cycle power plants such as Integrated Gasification Combined Cycle (IGCC). A range of hot gas filtration technologies have been under development for a number of years but further research is needed to enable widespread commercial deployment.


Acid rain

A number of technologies, collectively known as flue gas desulphurisation (FGD), have been developed to reduce SO2 emissions from coal use. These typically use a chemical sorbent, usually lime or limestone, to remove SO2 from the flue gas. FGD technologies have been installed in many countries and have led to enormous reductions in emissions. 

Reducing NOx emissions

The combustion of coal in the presence of nitrogen, from either the fuel or air, leads to the formation of nitrogen oxides. Technologies to reduce NOx emissions are referred to as either primary abatement and control methods or as flue gas treatment. Primary measures include the use of low NOx burners and burner optimisation techniques to minimise the formation of NOx during combustion. Alternatively technologies such as Selective Catalytic Reduction (SCR) and Selective Non-Catalytic Reduction (SNCR) lower NOx emissions by treating the NOx post-combustion in the flue gas. SCR technology has been used commercially for almost 30 years and is now deployed throughout the world, removing between 80-90% of NOx emissions at a given plant.

Trace elements

Coal is a chemically complex substance, naturally containing many trace elements including mercury, selenium and arsenic. The combustion of coal can result in trace elements being released from power stations with potentially harmful impacts to both human health and the environment. A number of technologies are used to limit the release of trace elements including coal washing, particulate control devices, fluidised bed combustion, activated carbon injection and FGDs.


The combustion of coal generates waste consisting primarily of non-combustible mineral matter along with a small amount of unreacted carbon. The production of this waste can be minimised by coal cleaning prior to combustion. Waste can be further minimised through the use of high efficiency coal combustion technologies. There is increasing awareness of the opportunities to reprocess power station waste into valuable materials for use primarily in the construction and civil engineering industry (see coal combustion products).


The Coal Resource

Coal Matters: Coal and Electricity Generation

Cornerstone, Vol 2, Issue 4

Alstom - Environmental Initiatives Reducing Emissions