Vertical farming limitations and potential demonstrated by back-of-the-envelope calculations.

Improving food security and reducing the environmental footprint of food production is urgently needed to satisfy the growing global population in a time of climate, biodiversity, and water pressures. Indoor vertical farming is largely independent of environmental conditions and is reported to reduce the land and water required for food production. However, vertical farming requires large amounts of energy. Based on the vertical farming energy cost, we derive from basic considerations a current minimum cost of ≈$10/kg dry plant matter. Vertical farming is therefore not currently competitive with dried cereals or pulses (e.g. wheat, rice, and soybeans). We also show limited current competitiveness for products like tomatoes and lettuce, despite a low dry matter content. Whereas the environmental implications of vertical farming depend on the electricity source. Using the average newly installed electricity mix in recent years (predominantly solar and wind, with some coal, natural gas, and bioenergy), vertical farming could substantially increase greenhouse gas emissions and has limited land benefits compared with conventional agriculture. Using exclusively electricity from photovoltaics, some environmental benefits could be achieved for crops with a low dry matter content like lettuce, but this is more limited for dried crops like wheat. The transparent calculations we provide here set out challenges for vertical farming and highlight that improvements in both the overall vertical farming energetic efficiency (≈1% to 2%), as well as low-impact electricity sources are needed in the future.