China pollution

Is burning ‘cleaner’ natural gas adding to China’s notorious smog?

Former government engineer backs use of the fuel, but says water vapour created by burning gas forms crucial part of chemical cocktail that produces smog and power plants must use equipment to catch the emissions

PUBLISHED : Wednesday, 28 December, 2016, 10:04am
UPDATED : Monday, 12 June, 2017, 12:53pm

Natural gas-fuelled power stations and household heaters, billed as a cleaner alternative to highly-polluting coal powered plants mainly used in China, are contributing to smog rather than helping tackle the problem, according to a retired senior government engineer whose research has been widely shared on social media.

The expert says it is right to use more natural gas to combat air pollution, but equipment needs to be installed to trap water vapour created by burning the fuel as it is playing a huge role in creating smog.

The mainland’s Ministry of Environmental Protection, however, has disputed the expert’s findings, saying his conclusions are flawed.

The controversy comes as large parts of China’s north were blanketed in thick smog earlier this month, much of created as power stations fuel heating systems during the winter cold.

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Li Chongxing, a former senior engineer at the Ministry of Water Resources, says that burning natural gas contains huge amounts of water vapour and that this combines with pollutants in the atmosphere to create smog.

He estimates that in Beijing alone enough water vapour is created each day by burning natural gas to fill a small reservoir.

His research paper was first published three years ago, but went viral on the internet in recent weeks amid the smog enveloping much of the north.

Li warned that the government’s negligence in failing to tackle the problem of water vapour would make the costly shift of switching from highly-polluting coal-fuelled power stations to natural gas ineffective.

“The latest round [of smog] confirmed my predictions,” he told the South China Morning Post.

“If we can collect condensed water from the chimneys of natural gas burners, we will not only reduce harmful vapour production but increase the overall efficiency of the burners with heat recycling as well,” he said. “Some universities have already implemented modifications to their natural gas heaters. Unfortunately, the authorities still turn a blind eye to the issue.”

Beijing burns more than 100 million cubic metres of natural gas daily during the winter and is the third largest user of the fuel among cities around the world behind New York and Moscow, according to the municipal government.

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The result of the high use of gas means that up to a third of the relative humidity in typical Beijing smog might come from natural gas burning, according to Li.

The Ministry of Environmental Protection held a press conference and invited several mainstream scientists to refute Li’s research last week.

The main argument was that man-made vapour counted for only a small fraction of the humidity in the atmosphere, maybe only one in a few hundred thousandths.

Such a small amount could not possibly make a significant contribution to the formation of smog, the experts argued.

But Li said the proportion of man-made vapour in Beijing’s motionless air could be much higher than the meteorologists’ estimate.

The Shuangyushu heat supply plant, a World Bank-funded natural gas project in Beijing, ejected 2,848 tonnes of water into the atmosphere with its 696 megawatts burners, according to his research.

Within a day it could increase the humidity to near saturation point in an area about 47 square kilometres if the air stayed motionless below 50 meters, which was usual in smoggy weather, he argued.

Within three days the vapour could spread and affect an area of 100 square kilometres, Li said.

A joint study published this month by a team of scientists from China, Germany and the United States found tiny water molecules in the air provided a warm bed for chemical reactions leading to severe smog in Beijing.

Sunlight also played a crucial role in these chemical reactions, the researchers argued.

This unique chemical process generated an enormous amount of pollutants such as nitrate and sulphate, the latter in amounts equivalent to a volcano eruption.

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Dr Su Hang, researcher at the Max Plank Institute in Germany and an author of the research, said Li’s general idea that water vapour contributed to smog was valid.

“The more water in the air, the easier the chemical reactions,” he said.

But Su did not agree man-made vapour should be blamed as a main cause of Beijing’s smog.

“The amount is too small compared to the vapour produce by nature,” he said.

“Pollutants in factory emissions and automobiles’ exhaust fumes, they are the real devils behind smog,” he said.