CHONGQING, May 27 (Xinhua) -- The county of Fengdu in southwest China's Chongqing Municipality is overhauling its cattle farms to cut pollution along the Yangtze River.

The county famous for beef has over 1,000 cattle farms, the largest with over 10,000 head. One of the country's largest beef producer Hondo Beef is headquartered in Fengdu. There are more than 210,000 cattle in the county, according to the county animal husbandry bureau.

"About four years ago, pollution from cow dung was alarming, and we had to take action," said He Chuandong, deputy director of the bureau.

"Farmers used to dump the dung near crop fields, and it frequently rains here, so there was heavy runoff," He said.

Rivers were darkened and grass along rivers died. "During winter when the river bed was exposed, cow dung could reach about a man's height," said a resident in Gaojia Township.

One cow produces 25 to 30 kilograms of dung very day. Consider the number of cow farms in Fengdu, the total amount of dung is huge, He said.

In 2014, the county invited Renmin University of China (RUC) to assess the environmental impact of cattle-raising. The county had a development target of 550,000 head, but later it cut the figure by 150,000 at the suggestion of RUC.

All big farms have renovated their sheds and built methane tanks to collect and compost manure. Factories have opened to produce organic fertilizer. Mushroom farms, an earthworm factory and a power plant were established.

Now 95 percent of dung is recycled, according to the bureau.

Farmer Zhang Lincong has 200 cattle. Every day, these animals produce about 5,000 kilograms of dung. "Not a single bit is wasted on my farm," said Zhang.

Zhang earns 20,000 yuan (about 6,340 U.S. dollars) every year from selling composted cow manure to the earthworm factory. He uses processed cow urine to fertilize his own corn fields.

Hondo Beef invested 80 million yuan to upgrade the sewerage system for its farms and butcheries.

"Environmental protection is the biggest priority if the beef industry is to be developed," said Wu Dongping, vice general manager of the company.

"As industry is consolidated, it is getting harder to find cow waste now," said Huang Jin, general manager of Fengzeyuan Fertilizer Co., Ltd.