SAN FRANCISCO -- China has already surpassed the U.S. in emitting greenhouse gases, according to some studies, but the picture may soon get better.

That's the word from Mark Levine, director of the environmental energy technologies division and group leader of the China Energy Group at Lawrence Berkeley National Lab at the Asia Society's Scaling Up Conference taking place in San Francisco.

"China is going to saturate on buildings in the near future," he said. "The pace of construction will go down."

As construction slows, so will pollution generated from producing steel, cement and other supplies, he said. Fifty percent of all new buildings in the world today are being built in China, he said. Roughly 50 percent of the worldwide supply of cement is made in that country and cement is an extraordinarily energy intensive process. "It's basically baking rocks," said Bruce King, a structural engineer and green building expert. Only six percent of cement gets made in India and 4 percent is made in the U.S., he noted. (Levine spends about half of his time in China.)

China is also seeding the market for energy efficiency, Levine added. The national government this year will invest $1 billion into building efficiency projects. The money is largely paid out in grants. Next year it will go to $2 billion. The year after that, the total will likely rise to $3 billion to $4 billion. The federal government is also insisting that provincial governments begin to come up with efficiency grants of their own.

American buildings are more efficient, but overall Chinese buildings consume only one-third of the power. "They don't overheat, overlight. They don't demand that we run air conditioning and heating at the same time," Levine said.

But it's all not good tidings. "The Chinese are making their buildings too fast and they are building too many too fast," he said. As a result, some of these could be quite shoddy and will add to landfills in the future.

China, overall, does not use nearly the same amount of energy to operate its buildings as the U.S., according to Qingpeng Wei, associate professor and deputy director of the building energy research center at Tsinghua University. (Tsinghua is China's MIT.) The U.S. consumes 22 percent of the energy in the world and 30 percent of the energy used in building operations, he said, citing Energy Information Administration stats.

China consumes 17 percent of the world's energy, while 12 percent of the total energy in the world is consumed by keeping lights and heaters running in malls, offices and homes. (Africa and India account for two percent each in both counts, the same as South Korea.)