BEIJING, May 10 -- China's largest coal producer Shenhua Group has completed upgrades to its coal-fired power plants in the Beijing-Tianjin-Hebei region that will dramatically reduce their emissions.

A milestone in China's efforts to be more environmentally friendly, Shenhua's upgrades will take emissions of dust, sulfur dioxide (SO2) and nitrogen oxides (NOx) from the company's 22 power units in the region below 10 milligrams per cubic meter, 35 milligrams per cubic meter and 50 milligrams per cubic meter, respectively.

This compares to current national emission standards for the three substances of 20 milligrams per cubic meter, 50 milligrams per cubic meter and 100 milligrams per cubic meter.

Following the change, annual emission of dust, SO2 and NOx by Shenhua facilities in the Beijing-Tianjin-Hebei region will go down by 84 percent, 71 percent and 83 percent, Shenhua said in a statement on Tuesday.

The upgrades took Shenhua three years and cost 2.35 billion yuan (360 million U.S. dollars), which translates into an added cost of 0.01 yuan per kilowatt hour (kwh) of electricity.

Shenhua said it will upgrade its facilities across China so they all reach similarly low emission levels by the end of 2020, bringing its carbon emission down to 835 grams per kwh of electricity produced from 892 grams in 2015.

"As more and more equipment will be made in China, the cost of the upgrades will probably go down in the coming years. Coal-fired electricity will remain an economical option for China," said Wang Shumin, Shenhua's vice president.

Shenhua's move to cleaner use of coal comes at a time when China is at pains to balance economic activity and environmental protection. The increasingly affluent Chinese are demanding the government do more to clean up the air and water.

While China is aiming to increase the share of non-fossil energy in its primary energy consumption to 20 percent by 2030, the rest will still need to come from coal, oil and gas.

To reconcile the use of coal, which China has in abundant supply, with a desire to increase use of renewable energy, adoption of clean coal technology has become the order of the day.

"The coal industry certainly needs a revolution and ultra-low emission technology could be part of the answer," said Xie Kechang, a member of the Chinese Academy of Engineering.