Pig dung used to be a serious issue in Longyou county, Zhejiang province. The waste produced by 2.8 million hogs raised in the county had fouled rivers here.

But Zhu Youbiao, a local farmer, has turned the county's mountains of dung into serious dough, with the establishment of Kaiqi Energy Technology Co Ltd in 2009.

"I had 25,000 pigs and dozens of tons of dung and urine needed to be dealt with every day," said Zhu.