History catches up with Hong Kong's 'green lifeline'

At 7 am it is already broad daylight in the city of Shenzhen and the air is pungent with the smell of animal waste. Wearing his blue uniform, Zeng Hui gets into a small control room, opens a barrier, and begins to release waiting vans.

Zeng is the customs officer of Wenjindu Port, which operates under Shenzhen customs. It is the most important and the only land route pass for agricultural products provided to Hong Kong from the mainland. More than 80 percent of such agricultural products go through this port.

In 2011 pigs delivered through the port made up 95 percent of Hong Kong's market demand and the cows 100 percent, prompting Wenjindu to be called the city's "green lifeline".