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China's carbon capture options and plans
Reuters
Wednesday, November 4, 2009
By Emma Graham-Harrison
BEIJING - China, the world's top emitter of greenhouse gases, is aiming for many more years of rapid growth fuelled by coal as its main energy source. Scientists are stepping up efforts to limit emissions by capturing and storing them.
But experts say the technology for carbon capture and storage (CCS), as the technology for confining emissions is usually known, is costly and parts of it are unproven.
Here are some key questions and answers about CCS in China:
WHAT ARE THE ADVANTAGES OF CCS?
The technology would in theory allow China to continue fuelling growth with coal, while controlling or even cutting the amount of carbon dioxide pumped into the atmosphere.
Some carbon-stripping technology could be retro-fitted onto existing power plants, avoiding the need to start rebuilding chunks of the nation's power infrastructure from scratch.
WHAT ARE THE DRAWBACKS?
The technology for capturing carbon dioxide is expensive and energy-intensive, reducing the amount of electricity generated for each tonne of coal and increasing its cost.
The technology for storage is still in the early stages.
Geologists need to check how easily gas can be injected into a potential store, and whether there are risks of leaks. There is also no consensus yet about issues such as creating stores in earthquake-prone areas, where they could crack open.
Some areas suitable for holding large quantities of gas may also be far from the power plants and factories pumping it out.
WHAT ARE THE POSSIBLE METHODS?
There are many different options for capturing carbon.
China's first commercial-scale demonstration plant -- now under construction -- will have pre-combustion capture, where coal is gasified and CO2 stripped out leaving hydrogen as a fuel.
Other options could allow CCS at existing coal-fired plants.
One is scrubbing the pollutant out of waste gases after coal has been burnt, which does not require building new infrastructure, but can be very energy intensive.
The oxyfuel method burns coal with oxygen rather than air, producing CO2 and water vapour, making capture easier.
Much discussion of CCS has focussed on power plants but it could be used in other sectors with high emissions, like steel.
China also has nearly 200 chemical plants with high-purity streams of CO2 that could be used for low-cost trials projects.
WHAT PORTION OF CHINA'S EMISSIONS COULD BE CAPTURED?
A recent study conducted with the European Union suggested that China could reduce emissions 36 percent from a base scenario for 2050 if it poured resources into carbon control plans including building 400 gigawatts of power plants with CCS.
This is a massive amount, equivalent to nearly five times Britain's current capacity -- but amounts to less than half China's own installed power capacity even now.
WHAT ARE CURRENT STORAGE OPTIONS?
One option is oil and gas reservoirs that have been emptied of much of their reserves. Oil firms already use carbon dioxide to help extract more fuel from emptying reservoirs, and the extra crude or gas gained can help offset costs.
But in China these can only hold a finite portion of forecast emissions and there are fears some could leak out through the thousands of old wells scattered across many fields.
Other options such as saline aquifers deep underground, or coalbeds deemed "unmineable," offer more storage potential but are still being investigated by scientists.
WHAT HAS CHINA DONE SO FAR?
China has a handful of pilot carbon capture and storage projects under development, including one demonstration plant in Beijing, where the gas siphoned off is used to carbonate drinks.
Construction has started on the GreenGen power plant that should start power production in 2011 and carbon capture in 2016.
China's biggest coal producer, Shenhua Group, also announced this year that it would install a CCS facility at its coal-to-liquids plant in Ordos, Inner Mongolia.
Sources: Reuters, China-UK Near Zero Emissions Coal Initiative (www.nzec.info), National Resource Defence Council, Pacific Northwest National Laboratory |
