From 2003 to 2009, the total grain loss from various natural disasters was 303.35 million tons - more than four times the increase in output over the same period, CAAS statistics showed.

"Nearly 60 percent of the grain loss is caused by drought. The other main causes of crop loss are floods, plant diseases and insects," said Li Maosong, a researcher on disaster reduction at the CAAS.

"Therefore, for China, reducing agricultural loss caused by natural disasters is as important as increasing output. Plant factories, keeping out most natural disasters that hit the country, will surely show its importance in the future.

"It can be built everywhere we want, even in deserts and on islands," he said.

By 2011, more than 20 plant factories spread over 10 provinces and municipalities in China have included 20 varieties of vegetables, CAAS statistics showed.

The varieties in plant factories in China still lag behind those in Japan, which has nearly 60 varieties, including not just vegetables, but vegetative medicinal materials as well, said Tong Yuxin, a CAAS researcher.

Japan accelerated its construction of plant factories after a devastating earthquake and tsunami last year created nuclear pollution, Tong said.

"Building more plant factories is a good choice for Japan in its stricken areas, where it is not safe to plant crops on land because of nuclear pollution," she said.

According to Yang, with a total investment of 150 billion yen ($1.9 billion), Japan is expected to triple the number of plant factories to 150 within the next two to three years.

Vegetables from plant factories do have one disadvantage, at least for now.

Agriculture professionals said that because of the high cost of production, the price of vegetables grown in plant factories is several times higher than that of common vegetables.

For instance, a head of lettuce grown in a plant factory with artificial light now sells for about 15 yuan ($2.40), about five times more than an ordinary one.

"I just buy and try. I cannot afford this over a long time," said a local resident in Shuangan Department Store in Beijing.

Yang agreed. "What we need to do now is try to lower the cost of planting vegetables in plant factories, so that such products can go on the market in large quantities to benefit more people," he said.

Yang urged authorities to offer subsidies to enterprises that want to build plant factories.

"Apparently, the importance of such advanced technology to ensure food safety in China has not been realized among many officials," he said.

jinzhu@chinadaily.com.cn