Currently, over a quarter of the world's primary energy supply comes from coal. Since the rich world has already created its coal infrastructure, the increased use of coal in China and India is now under scrutiny. In 1980, rich countries used over 65 per cent of the world's coal; in 2000 their share was roughly 50 per cent.
By 2005, this figure fell to 38 per cent as consumption in China and India grew. 'China is building one power station a day', newspaper headlines scream. Western green groups want a moratorium on coal-based power stations funded by multilateral agencies like the World Bank. But they overlook the fact that the use of coal in the US and Australia has continued to grow, even after the Kyoto Protocol- 150 new coal projects will be built in the US alone.
Even the UK, which earned huge benefits by moving to natural gas, is revisiting its options. The price of oil, controlled by 'unstable' governments, is making coal attractive again. And not just in China.
Coal is dirty. It emits co2, particulates and oxides of sulphur and nitrogen; it generates huge waste in the form of flyash. In addition, power plants consume large quantities of water and discharge equally large quantities of wastewater. These impacts were already driving 'green' technology for coal. The imperative of climate change is pushing proponents of coal to reinventing technologies for 'clean' and 'new' coal.
There are three technology approaches available. One is to increase the thermal efficiency of current technology. Higher efficiency reduces coal consumption in electricity generation, thus reducing co2 emissions. Technologies to increase efficiency are clean-coal technologies.
One of the ways to increase efficiency is to increase the pressure and temperature at which steam is fed to turbines. Subcritical power plants (the bulk globally) operate at 163 bar pressure and 538°c. The best of these plants have an efficiency of 36 per cent. For the best in India this goes down to 32 per cent.
At the next level are supercritical plants in which the pressure is over 244 bar and temperature over 550°c. With 170-plus plants of this type in the world, this technology is getting established. By 2006, in China, 6 per cent of coal-fired plants were based on this technology.
Finally, there are ultra-supercritical plants, in which pressure is over 350 bar and temperature exceeds 600° c. This gives them an efficiency of 45 per cent.
Then there are technologies called fluidized bed combustion (FBC) and pressurized FBC cycle in which crushed coal is suspended on upward blowing jets of air during combustion. The result is a turbulent mixing of gas and solids, providing more effective chemical reactions and heat transfer and burning of coal with greater efficiency.
The other promising technology is the integrated gasification combined cycle (IGCC), which can give 50 per cent efficiency. The challenge is to lower costs and make it work with different kinds of coal. In this technology, coal is gasified under pressure with air/oxygen to produce gas, which is burnt in a gas turbine to produce power. There is a double gain as exhaust from the turbine can pass through a heat-recovery steam boiler, which generates more power. Only four plants using this technology have been built successfully-in Europe and the US.
The second approach is 'new coal' technologies. Instead of burning coal in conventional fashion, this approach will either convert coal into gas or recover gas trapped in coal seams underground. These gases can be burnt cleanly.
The third option is simpler-we continue to use coal, but the CO2 that is emitted is captured, compressed and transported for underground storage. This technology, carbon capture and storage, is being touted as the most promising option, allowing us to keep the coal-based energy economy going.
Currently, the world has three large-scale storage projects in operation, each involving 1 million tonnes of CO2 a year, in Sleipner, Norway; Weyburn in Saskatchewan, Canada, where gas from a project in North Dakota in the US is buried; and Salah in Algeria. This technology is being pushed by industry and NGOs alike. Groups like the Worldwide Fund for Nature (WWF) and the Natural Resources Defense Council (NRDC) have backed this technology.
In October 2007, the US energy department committed US $197 million for three new carbon-storage projects in the country. Coal-rich Australia is proposing four projects and wants to develop legislation to license and monitor facilities. The biggest is proposed in the Latrobe Valley. This is a joint venture between mining giant Anglo American and oil multinational Shell, to first turn coal into liquid diesel and pump CO2 into a depleted oilfield some 80 km offshore in the Bass Straits separating mainland Australia from Tasmania. This project will sequester 50 million tonnes of CO2 a year and could pave the way for the rest of Australia to pump its waste into the Bass Straits reservoir.
Cost and safety are crucial issues. According to IEA, a big supporter of this technology, the lowest costs achievable at greenfield coal-fired plants could go up to US $50 per tonne of CO2. This includes capture costs of US $20-40 per tonne, transportation costs of US $1-5 per tonne per 100 km and storage costs of US $2-5 per tonne. Given improvement trajectories, IEA says, the total costs could drop below US $25 per tonne by 2030.
But many dispute this 'rosy' prognosis. They say this technology is unsafe. CO2, which liquefies under pressure underground or in a pipeline, is acidic and can cause asphyxiation in high concentrations. Leakages can thus cause disaster for such units.
Still many are banking on this technology to fix the climate change challenge quickly and painlessly. The problem is we are running out of time and can't afford another 'bad' idea. The dream of burying waste will let the world continue to pollute.
Planners see no option but to invest in coal because it is cheap and domestically available. In 2005, coal generated roughly 70 per cent of electricity. Currently known coal reserves-250 billion tonnes-are expected to last another 50 years. The current annual consumption of 400 million tonnes is expected to increase to 2 billion tonnes by 2030. There are 81 coal-based power stations and many more are planned.
DTE Team
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