China's capital city plans to reduce coal usage in an effort to reduce pollution.

Beijing has reduced its cap for annual coal consumption to 15 million tons by 2015, from an earlier reduction of 20 million tons for the same time period, Beijing's development and reform commission announced Sunday, state-run news agency Xinhua reports.

In 2010, Beijing consumed 26.35 million tons of coal, accounting for 30 percent of the city's total energy consumption. During the 1990s, coal accounted for more than 40 percent of Beijing's energy consumption.

As for countrywide coal consumption, the China Electricity Council said in a report last week that it expects China's power sector to consume more than 2.1 billion tons of coal this year, an increase of about 150 million tons year-on-year.

To help achieve Beijing's new coal reduction target, four of the city's major coal-burning power plants will be replaced with natural gas-running plants, said Zhao Lei, deputy director of the commission.

The commission also said it will replace all coal-fired equipment in its core areas by 2013.

The Beijing government has spent $1.9 billion over the last two years replacing coal-fired heating systems for 160,000 households. Residents who rely on electricity for winter heating are eligible for government subsidies.

An environmental expert, speaking to Xinhua on condition of anonymity, said he wasn't optimistic about Beijing's targets for coal reduction.

Making the switch to gas, he said, would require time and a huge investment to build more natural gas pipelines. Furthermore, it would be "extremely hard" to ban the 2.15 million small coal furnaces operating in the city, he said.

Environmentalists are also calling for regional cooperation in reducing Beijing's air pollution. Neighboring Hebei province and Tianjin municipality, for example, consume 280 million and 47 million tons of coal a year, respectively, compared with Beijing's 26 million tons.

"Beijing cannot 'do it alone' in the fight for cleaner air. Regional cooperation is indispensable," said Wang Siyue, an atmospheric physicist with the Chinese Academy of Sciences.

A Beijing Bureau of Environmental Protection report last year said that pollution from the city's neighboring regions is the largest contributor to the city's PM2.5 reading, a scientific measure of fine particulate matter in the air, 2.5 micrometers or less in diameter.

Last month Beijing announced it would begin posting PM2.5 readings, as part of its measures to reduce air pollution. Previously the city had based its air quality information on readings of PM10, particulate matter at least 10 micrometers in diameter.