The bureau forced the two companies to take part in the tiny trial this year. More factories and plants will join next year if the trial goes well, the bureau said.

Du Chengzhang, deputy manager of the coal-fired Huaneng Beijing Cogeneration Power Plant, told reporters, "We need more support from the government such as tax cuts, financial aid and policy support." Without more government support, the company might not turn a profit, he said.

Du said that the company would invest 180 million yuan ($29 million) in foreign green technology, which would help to reduce by 50 percent its emissions of the pollutants that generate the small and deadly particles of pollution known as PM 2.5.

"It's not realistic to let companies like us pay for all the expenses on green investment," he said.

Feng Zhihong, manager of Jinyu Taihangqianjing Cement Company, said that as part of the pilot program, his company spent nearly 5 million yuan on purchasing equipment to scrub nitric acid from its smokestack. "The government promised to cover all the costs, but we spent this money from our own budget," he said.

Zheng Zaihong, deputy director of the bureau, agreed with the companies, warning, "The government needs to offer these companies more support because they still need to make money on their own."

"This is a long-term process that must be settled," he said, noting he is unclear when the trial would come to an end and the regulations will be applied to all companies across Beijing.