A question many growers are asking is whether vertical farming of hydroponic lettuce production is profitable. Light requirement (daily light integral, DLI) of lettuce can vary from 15-20 mol/m2/day. Lettuce grown under low DLI has slow growth rate (i.e., takes longer to harvest) and appear poor in quality (elongated). Current estimate is that energy costs for lighting alone can be 40 to 50% of return from sale of lettuce, making it challenging to make profits. The sustainability of vertical farms will mainly depend on developing research based solutions for decreasing energy costs. In our lab, we are testing different lighting systems, mostly LEDs, for their efficiencies, energy costs and effect on plant growth. We are also building biofeedback systems that reduce overall energy (for lighting) consumption in vertical or indoor farms.
