China has some of the world's worst water pollution. And the country's farms are responsible for a big part of that problem. So there is a certain irony in visiting a farm here that purports to actually help reduce pollution from other sources. But that's the claim of a 100-acre hydroponic farm in China's southwest.
The farm on the edge of Dianchi lake grows some 30 types of vegetables, including long green rows of lettuce and spinach that sway in the wind and float on platforms with their roots in the water.
Where other farms would need fertilizer to provide nutrients for their crops, the vegetables here get their nutrients from sewage that's been dumped in the water by the city of Kunming and its environs. Sales representative Cao Jiangrui said that's all the fertilizer they need. She said government inspections to prove the vegetables are safe to eat, and that by putting the nutrients to use, the pilot project helps, in a small way, to clean up Dianchi lake.
Dianchi is a sprawling, shallow lake, about 25 miles long and 5 miles wide. It was once a source of drinking water for the city of Kunming. But that was before China's economic boom took off, the flow of pollution into the lake exploded, and the water near the shore became a stinking, foaming green and black swirl.
Today, the stench is gone, and the water looks more normal, if still far from clear. Most of the change has come from new policies by the local government, which has shut down polluting factories, ordered idle sewage treatment plants to restart, and is more closely monitoring pollutants like sewage and pesticides. Observers here say the hydroponic farm is another promising approach
Chemical engineer Jiang Li Hong of the Kunming University of Science and Technology monitors water quality for the project. She said the improvement in the quality of water that flows through the farm is dramatic–the vegetables remove 95 percent of the ammonia, and up to 60 percent of the phosphorus and nitrogen, which can choke the oxygen out of the lake but are just what the vegetables need.
Jiang said the hydroponic farm is a good start in attacking Dianchi's problems. But she'd like to see the project expand from 100 acres to 7,500 acres–a scale at which, she said, it could make a real difference.
The hydroponic farm is one of a number of government-funded projects around Dianchi to try to clean up the lake and change its image from cesspool to success story. In another project near the farm, teams of farmers plant vegetation on the lake's shore, meant to absorb toxins from the water.
Forty year-old farmer Jin Hong said he swam in the lake when he was young, and that villagers could drink from it. Then came the factories and their toxic waste, then the sewage from the expanding city.
It's much better now, he said. Still, the water's far from clean. When asked whether he would eat vegetables grown with water from the lake, Jin looks amused, then said local farmers have been using it for more than 20 years. "It's the only water we've got," he said.
Yunnan University, senior life sciences professor He Shuzhuang also looks amused, and gives a similar answer to the same question.
"In mainland China, it is a difficult problem," He said. "Maybe over 90% of vegetables or crops are all polluted. We have to take it because we have no other choice."
He said it's good that Kunming's government is getting more serious about cleaning up the lake. But he said there's a big disconnect, because local leaders aren't interested in limiting the city's sprawl. Instead, they're following the lead of Beijing, Shanghai and other Chinese megacities by putting growth ahead of environmental concerns. Kunming has tripled in size in the past 20 years, wrapping itself around the northern part of the lake, which happens to be on a fault line.
"It looks like the government is making a bomb," He said, "and the bomb is getting bigger and bigger. We hope to keep some ground for the crops, but they try to make it all become the city."
If the city keeps expanding at its current pace, He said the remaining cropland around Dianchi will be gone in just three years, and more sewage will likely be going into the lake. That could mean that the hydroponic farm, rather than expanding and serving as an example for other polluted areas in China, may end up only as an example of what might have been.