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China in heated debate over turning coal into gas

Scientists are caught in a heated debate on whether China’s efforts to turn coal into gas would become an environmental disaster for the whole planet.

China is building the world’s largest synthetic natural gas industry, with more than 40 plants under construction or planned. When completed, these facilities would generate nearly 200 billion cubic meters of natural gas annually, more than the nation’s total natural gas consumption last year.

Converting coal to gas as fuel for power generation could significantly reduce the discharge of air pollutants, such as fine particulates into the environment. To the Chinese government, the technology is considered a major weapon in the battle against smog.

But a joint study by researchers from Duke University and Stanford University in the United States in 2013 alleged that these massive projects in China could emit four times more carbon dioxide than coal-fired power plants, while generating the same amount of energy, due to the lengthy chemical reactions required by the sophisticated conversion process.

The study prompted international concerns. If all the coal-to-natural-gas plants planned by the Chinese government were built, they would emit more than 1 billion tons of carbon dioxide each year, according to Greenpeace.

That was almost equivalent to half of the total CO2 emissions by India in 2013.

A new study published in the latest issue of journal Nature Climate Change by a team from the Chinese Academy of Sciences’ Institute of Engineering Thermophysics has challenged the US study.

The carbon footprint of the Chinese synthetic natural gas industry had been severely exaggerated due to an error in calculation, the Chinese team reported.

The actual CO2 emission intensity was only 1.35 – 1.60 times that of coal fire power plants. With the adoption of new technology, the emissions could be cut by at least a third, the Chinese study said.

“Moreover, in coal chemical plants that emit high concentrations of CO2 (such as coal-to-SNG plant), it is possible to capture CO2 with relatively low energy consumption and cost penalties. Therefore, the life-cycle GHG (green house gas) emissions from the coal-to-SNG process can be further mitigated if CO2 capture is applied,” the Chinese researchers wrote.

The US team admitted they made a mistake, but insisted their “broad conclusions” remained intact.

“…even if the carbon footprint of coal-to-SNG-to-electricity might someday become comparable to coal-to-electricity, it remains a technology of relatively high CO2 and water footprints,” the US researchers wrote in a response letter published in the same issue of the journal.

“Another major conclusion in our original paper concerned the high water consumption of SNG,” the US researchers said.

The Chinese study did not address or mention the many important water issues or other environmental impacts created by the synthetic natural gas industry, they said.

Professor Bi Jicheng, a researcher with the Institute of Coal Chemistry in Taiyuan, Shanxi province, said the debate was heated in the research community, but it was unlikely to change the nation’s adoption of the technology.

“Turning coal to gas has many problems, but we don’t really have a choice. We can’t give up on coal,” Bi said.

China is short on oil and natural gas reserves, relying heavily on imports. Coal, however, is abundant in the country and contributed more than 70 per cent to the country's energy supply.

 “If you live in China, you will fret about smog more than carbon dioxide,” Bi said.

source: http://www.scmp.com