It aims to make coal ‘a viable technical, environmental and economic case for continued use’. But should that be an aim?
The world’s first large-scale power station equipped with carbon capture and storage (CCS) technology officially opened in Canada this October, with the aim of making coal “a viable, technical, environmental and economic case for the future”.
This 1.35 billion dollar facility captures carbon dioxide (CO2) released from the 110 MW unit coal-fired Boundary Dam power plants near Estevan, Saskatchewan, and transports the same via pipelines to nearby oil fields where it is used for enhanced oil recovery. The left-over CO2 which is not used in the oil recovery is permanently stored deep underground. (See ’How Carbon is captured and stored in a power plant’)
Though seen and hailed a saviour technology by coal lobby group, and with US Environmental Protection Agency pushing for CCS as a technology to reduce CO2 emissions from thermal power plants, the question still remains whether it is worth investing in CCS when cheaper renewable energy technologies have been proven. (See ‘Cost of renewable technologies and CCS)
|Cost of renewable technologies and CCS|
|for 963.6 million units power production* or 110 MW coal equivalent plant running at 100 per cent plant load factor||Cost in Rs (crore)|
|CCS retrofitting with a coal firing unit||7,301.2|
|Solar Photovoltaic Plant||1,598.5|
|Wind Power Plant||1,012|
|Biomass based Power Plant||1,040.45|
|Renewables cost calculated based on levelised cost of generation figures from
|How carbon is captured and stored from a power plant?
Post-combustion has the advantage that it can be retrofitted to some existing power stations, which will generate much of the world's CO2 for decades to come. The process is energy expensive as scrubbing CO2 out of flue gas requires considerable amount of energy. The Boundary Dam project, run by Sask Power in Canada, uses this technology.
Pre-combustion CCS: Pre-combustion CO2 capture is a process where the carbon in the fuel is separated, or removed, before the combustion process. Instead of burning coal or natural gas in a combustion plant, the fuel can be converted to hydrogen and CO2 prior to combustion. The CO2 can then be captured and stored, while the hydrogen is combusted to produce power.
The downside is that it cannot be retrofitted. But it is seen as a good option for new plants. One of the large-scale pre-combustion CCS plant which is scheduled to start this year is the $2.7bn Kemper County gas project in Mississippi.
Oxyfuel-combustion CCS: Oxyfuel combustion with CO2 capture is very similar to post-combustion CO2 capture. The main difference is that the combustion is carried out with pure oxygen instead of air. As a result, the flue gas contains mainly CO2 and water vapour, which can be easily separated. The challenge is that it is expensive to produce pure oxygen. No NOx pollutants are formed, reducing scrubbing costs. But this technology can only be used in new plants and an air-separation unit has to be built to provide the oxygen. This approach is being used for a proposed new plant at the Drax coal-fired power station in the UK, currently one of the nation's biggest polluter.
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