Vertical farming: productivity, environmental impact, and resource use. A review

Vertical farming is gaining attention as an indoor growing system because it enables standardised and intense production, thanks to fully controlled growing settings where environmental parameters can be precisely tuned to satisfy plants’ needs. While vertical farming is claimed to feature high use efficiencies of land, water, and nutrient resources, its high energy use is behind some recent major bankruptcies and hinders large-scale uptake of the technology. Thus, a critical analysis of the productive, economic, and environmental performances of vertical farming is needed. Here, we review the state of the art of vertical farming, with the aim to provide quantitative data on productivity and environmental performance, with a focus on resource use efficiency, which can also be used for benchmarking. The article elaborates on how vertical farming compares with open-field and greenhouse production of leafy greens (in particular lettuce). Lettuce yield (as fresh weight, FW, per cultivation area) in vertical farms commonly averages 60 to 105 kg FW m−2 year−1, with energy use efficiency of approximately 0.08–0.13 kg FW kWh−1, and water use efficiency of approximately 140 g FW L−1 H2O. The higher greenhouse gas emissions of vertical farming technology systems (on average, 2.9 kg CO2 kg−1 FW) as compared with traditional systems are discussed and compared to impacts associated with transport in longer supply chains or those caused by energy-intensive greenhouse technologies that enable cultivation in harsh environments. The potential for consistent production throughout seasons in vertical farming suggests that looking at yearly yield only (rather than their monthly trends) may be misleading when addressing a stable food supply in a specific region.