The company produces an average of 15,000 tons of solid biofertilizer and 16 million kilowatt-hours of electricity each year.

And as China prioritizes modernizing its pig farms, cutting down on pollution and reining in use of agrochemicals, there is huge potential for Kaiqi.

Biofertilizers are already a 20 billion yuan market in China and their usage could double by 2020, according to Chemlinked, a market research company that specializes in China's agrochemicals market.

Years ago, most farms simply dumped their mounds of droppings into the nearest river. Thirteen of the county's waterways were officially classified as "black and smelly" or "garbage" rivers, not fit even for industrial use, said Wu Guoxiong, a pig farm owner.

Now, Longyou's rivers are running clear. By 2016, there were no "black and smelly" or "garbage" rivers left in the county, according to the county's water resources bureau.

Kaiqi has also received delegations from Fujian, Jiangxi, Henan and Jiangsu provinces investigating the possibility of replicating its model in their regions.

Contact the writers at qinjirong@chinadaily.com.cn

Zhu Youbiao, founder of Kaiqi Energy Technology Co Ltd, shows the brown liquid fertilizer made from pigs' excretions. Feng Chonglin / For China Daily