Her grandson, Zhang Yang, who serves as the co-op's chief, says Liao has salted duck eggs for the family since she married his grandfather at age 16.

"We'd be soaked with sweat and have lost a lot of salt while working in the fields," he recalls.

"Grandma would make salted eggs and share them to make sure we had enough (electrolytes) and didn't faint."

The family opened a small shop selling necessities in the 1970s.

"But sales were poor. Sometimes, if it rained, we wouldn't get a single customer all day," Zhang recalls.

"While we were trying to keep our shop afloat, we started improving the taste of our eggs. We later standardized the entire process and designated a specific ratio of mud and salt to achieve the best flavor."

They set up the cooperative with 28 households and started selling the eggs online when the local government began to vigorously promote e-commerce in 2015.

They initially used a dozen clay jars to preserve eggs in their yard. Sales picked up, so they emptied half a house and filled it with hundreds of urns that could ferment 50,000 eggs at a time.