The aim of this guide is to explore whether clean coal is really clean, or whether it’s as bad environmentally as regular coal.
To do this, we look at the impact of clean coal technology on emissions and air pollution, as well as a range other eco friendly benchmarks and indicators.
(Note – whether clean coal is actually ‘clean’, is a separate question to whether clean coal is feasible, or whether it has a practical long term future. You can read more about the pros and cons of clean coal technology in this guide.)
Summary – Is Clean Coal Really Clean?
In general, clean coal is cleaner than a coal plant that doesn’t use clean coal technology, but most likely not as clean as natural gas (depending on whether you count leaked natural gas in the mining stage), nuclear or various forms of renewable energy
There are many variables to clean coal such as what measure of ‘clean’ you are measuring, as well the clean coal technology being used (e.g. a bag filter has a completely different impact and level of effectiveness than the newest form of CCS or gasification that is still in the developmental stage)
Each coal plant is going to be different with how clean and eco friendly it’s energy production process is because of different variables involved in that process at each location
Some of these variables include:
– The type of coal used,
– the way coal is handled between the coal mine and the coal plant,
– the type of coal plant used,
– whether coal is pulverised or gasified,
– whether there are emission or pollutant devices installed at the plant,
– and how by-products and waste are treated or used
These factors can all impact how clean the coal-to-energy process is. There are also other factors that can have an impact too.
A factor like increasing plant efficiency won’t decrease the rate of pollution or emissions per unit of coal burned, but can decrease overall coal used to generate the same amount of electricity and can contribute to lower total pollution or emission amounts for that same amount of electricity.
Other factors like imposing new coal plant license conditions or putting in place carbon taxes don’t directly reduce emissions and pollution, but can do so indirectly
Clean coal also has it’s own drawbacks, such as being costly (therefore raising the end price of clean coal electricity), and in some cases, energy intensive and unreliable.
Several clean coal plants and clean coal technology projects have had to be discontinued or shut down at the pre construction, construction and operation stages, because of cost, complication and unreliability factors (amongst other factors such as applying technology at scale, just as one example)
So, we can’t look at how effective clean coal technology is without looking at the feasibility and practical side of actually using it to deliver energy and electricity (there’s no use in electricity that is overpriced and unreliable to both investors and consumers)
Often, only the areas of carbon emissions and air pollutants from the burning of coal are looked at in terms of impact on the environment, but a more complete picture may also look at type and extent of mining required, the coal plant process, what is done with flue gas, and what is done with coal plant waste and by-products.
This provides a more complete picture than just the ‘at plant’ eco footprint
How Can Coal Be Made Cleaner?
The two main ways are:
By reducing greenhouse gas emissions like carbon dioxide
By reducing air contaminants like nitrogen dioxide, sulfur dioxide and particulate matter
Other ways might include reducing the negative impacts of the coal mining process, and treating, disposing of or re-using coal plant waste or by products (such as coal ash) in a sustainable way.
Below, we have summarised how effective some of these technologies and methods might be, or what impact they might have on the coal energy production process.
(Note – these eco savings and reduction estimates below are guides only – actually savings and reductions depends on individual coal plants and technology. There should be testing and auditing bodies that provide accurate assessments in each area so that coal energy in general can be tracked for it’s eco suitability)
[Some Chinese estimates indicate] Coal washing can remove 50%-80% of ash and 30%-40% of total sulfur (or 60%~80% of inorganic sulfur) in coal
Carbon Capture Storage (CCS), Carbon Capture & Use (CCU), & Other Carbon Capture Technology
The IEA says … as much as a 12 percent reduction in carbon emissions can be achieved by 2050 through CCS.
… while CCS may have an overall positive effect on air pollution, emissions of some pollutants may increase
The Carbonate Looping Process can be used to separate more than 90 per cent of the CO2 released during the combustion of fossil fuels.
Retrofitting existing power generation facilities and industrial plants with this technology would allow them to be operated in a much more environmentally-friendly manner
Bag & Fabric Filters
Power stations … that haven’t fitted fine-particle bag filters … jump off the charts in terms of fine particle pollution
Bag filters can help reduce the amount of PM 10, or particulate matter smaller than 10 microns that power stations release.
At this size, particles can enter the lungs and bloodstream.
But bag filters are less effective for particles referred to as PM 2.5, or particulate matter smaller than 2.5 microns
… fabric filters [together with electrostatic precipitators] can remove 99% of the fly ash from the flue gases
[mercury emitted by coal-fired power plants] can be solved with mercury absorbers
Electrostatic precipitators [together with fabric filters] … can remove 99% of the fly ash from the flue gases
Electrostatic precipitators … [are] considered best practice for capturing emissions from brown coal
Flue Gas Desulfurization
Flue gas desulfurisation reduces the output of sulfur dioxide to the atmosphere by up to 97%, the task depending on the level of sulfur in the coal and the extent of the reduction.
Low NOx Burners
Low-NOx burners allow coal-fired plants to reduce nitrogen oxide emissions by up to 40%.
Coupled with re-burning techniques NOx can be reduced 70% and selective catalytic reduction can clean up 90% of NOx emissions.
New High Efficiency, Low Emission Coal Plants, Or Upgrade Of Existing Plants
… if existing coal plants were upgraded to high-efficiency, at least 19 percent of total emissions can be reduced on an annual basis.
Ultra-supercritical (USC) HELE technology … reduces emissions and fuel costs to about 75% of subcritical plants
Increased efficiency of plant [in general] – up to 46% thermal efficiency now (and 50% expected in future) means that newer plants create less emissions per kWh than older ones
[Super critical brown coal plants in Australia … would still be more emissions intensive than the majority of Australia’s existing coal plants]
… which type of steam cycle is used [in a new power plant] has no impact on the emissions per tonne of coal burned
… The only difference between different steam cycles in terms of emissions is how much power they can generate from one tonne of coal
Emissions per tonne of coal depend solely on the amount of sulphur contained in the coal
You can find out more information on the different types of new coal plants and their efficiency rates at:
Gasification & Combustion Techniques
Advanced technologies such as Integrated Gasification Combined Cycle (IGCC) and Pressurised Fluidised Bed Combustion (PFBC) enable higher thermal efficiencies still – up to 50% in the future
Coal Stations Licenses & Permits
[Coal station licenses and permits with conditions of] greater emissions controls and more accurate reporting measures [can help reduce emissions and air contaminants].
[But, this can make coal electricity prices more expensive too].
National Air Pollutant Monitoring Bodies
[the intention of these bodies is to control air pollution … but the NPI in Australia isn’t working as intended]
… a national air pollution monitoring body, similar to the United States Environmental Protection Agency [is needed to help control air pollution].
General Notes On The Impact Of Clean Coal Technology
… there is the claim that other clean coal technologies can be applied to reduce the emissions of nitrogen oxide and sulphur oxide; increase coal combustion efficiency; and remove coal impurities to reduce emissions.
[It’s important to note that clean coal probably has little impact of mining on the environment – which can be fairly damaging. It’s more so focussed on the coal itself and the coal burning process only the burning of coal]
… power stations in Australia should be updated with emission control technology, which could reduce the release of toxins by up to 90%
… when old high emitting plants shut down … the data should show a really significant reduction in the toxic pollutant levels. [So, reducing both the number of coal plants overall, and the number of old coal plants can reduce toxic pollution from coal plants separately from installing or using any clean coal technology]