In an 8.8-meter-tall automated plant factory in Chengdu, Sichuan province, rows of lettuce bathe in red light on 20-layer cultivation racks and grow at twice the normal rate.

The vertical farm facility, covering just 100 square meters, was developed by the Institute of Urban Agriculture of the Chinese Academy of Agricultural Sciences. It can produce up to 50 metric tons of lettuce annually.

"The factory enables full control over light, temperature, water, nutrients and air. The entire production process, from seeding and transplanting to harvesting and packaging, is handled by robots," said staff member Shi Xianglian.

Shi said the growth cycle for lettuce here is only 30 to 35 days — half the time needed in traditional open-field farming — while yield per unit area can reach up to 120 times that of conventional methods.

With soilless cultivation in a sterile environment, the system eliminates pests and diseases, ensuring the produce is free of heavy metals, chemical additives and pesticide residues, she added.

Wang Sen, a researcher at the institute, said a core technology of the vertical farm is the use of artificial light to ensure efficient photosynthesis. He explained that LED lights are used to offer specific "recipes" — varying in color, intensity and duration — to suit different plant species and growth stages. After years of research, the institute has developed over 1,300 such light formulas. "Despite the high production efficiency, operating costs remain a bottleneck," Wang said, noting that electricity for artificial lighting and temperature control accounts for about 70 percent of total operating expenses.

"Currently, producing one kilogram of lettuce in such a facility costs between 10 and 15 yuan ($1.5-2.2), significantly higher than traditional methods," he added.