Wheat yield potential in controlled-environment vertical farms

Abstract

Scaling current cereal production to a growing global population will be a challenge. Wheat supplies approximately one-fifth of the calories and protein for human diets. Vertical farming is a possible promising option for increasing future wheat production. Here we show that wheat grown on a single hectare of land in a 10-layer indoor vertical facility could produce from 700 ± 40 t/ha (measured) to a maximum of 1,940 ± 230 t/ha (estimated) of grain annually under optimized temperature, intensive artificial light, high CO₂ levels, and a maximum attainable harvest index. Such yields would be 220 to 600 times the current world average annual wheat yield of 3.2 t/ha. Independent of climate, season, and region, indoor wheat farming could be environmentally superior, as less land area is needed along with reuse of most water, minimal use of pesticides and herbicides, and no nutrient losses. Although it is unlikely that indoor wheat farming will be economically competitive with current market prices in the near future, it could play an essential role in hedging against future climate or other unexpected disruptions to the food system. Nevertheless, maximum production potential remains to be confirmed experimentally, and further technological innovations are needed to reduce capital and energy costs in such facilities.

Keywords: vertical farm; wheat; yield.

Fig. 1.

Comparison of crop model simulations with observed wheat growth and yield in 1 y. (A) Observed (symbols) and simulated (lines) values for total biomass (circles, dashed lines) and yield (triangles, solid lines) for wheat grown in fields at Merredin, Australia (yellow); Wageningen, The Netherlands (green); and Xiangride, China (purple) (15). (B) Observed (symbols) and simulated (lines) values for total biomass (circles, dashed lines) and yield (triangles, solid lines) for an indoor experiment with 20 h of 1,400 μmol/m²/s light (50 MJ/m²/d, with 1 J = 1 W/s) at 330 ppm atmospheric CO₂ and five successive replicate harvests (13). Yields and total biomass (yield plus straw) are shown at 11% grain moisture. Simulations were done with the DSSAT-NWheat crop model.

Fig. 2.

Annual field and indoor wheat yields. Observed wheat yields from the field (gray bars) and an indoor controlled environment pilot experiment (blue bar), and simulated mean yields from two crop models for wheat cultivars with a low harvest index (green bar) and a theoretical high harvest index (red bar) grown in an indoor controlled environment. Error bars show SEM for the field, SD of the indoor experiment, and ± the mean of the 10th and 90th percentiles of the indoor simulations. Yields are shown at 11% grain moisture. ¹10-y average yield, 2008–2017 (2). ²Guinness World Record, 2017 (14). ³Observed 70-d season indoor experiment with 20 h of 1,400 μmol/m²/s light daily (50 MJ/m²/d) and 330 ppm atmospheric CO₂ concentration, scaled up to 1 ha and multiplied by 5 harvests/y (13). ⁴Simulated 1-ha indoor experiment using the DSSAT-NWheat and SIMPLE models with 70-d seasons and 5 harvests/y with constant light and 1,200 ppm atmospheric CO₂. The average of simulations with 1,800, 1,900, and 2,000 μmol/m²/s light (77, 81, and 86 MJ/m²/d, respectively) and ±10% RUE is shown. ⁵Simulated 1-ha indoor experiment using the DSSAT-NWheat and SIMPLE models with 70-d seasons and 5 harvests/y with constant light, 1,200 ppm atmospheric CO₂ and a theoretical harvest index of 0.64 (24). The average of simulations with 1,800, 1,900, and 2,000 μmol/m²/s light (77, 81, and 86 MJ/m²/d, respectively) and ±10% RUE is shown.

Fig. 3.

Annual cost and return for indoor wheat farming. (A) Pie charts showing 2019 (Left) and 2050 (Right) breakdown of costs as percentages for a 1-ha, 10-layer indoor wheat growing scenario with an adapted high harvest index cultivar (the theoretical scenario in Fig. 2 and SI Appendix, Table S4) and capital and building costs financed at 5% per year. A breakdown of the costs for simulation and experiment scenarios is provided in SI Appendix, Fig. S2. (B) Total annual cost of wheat production (lines) and annual returns (stacked bars) for a 1-ha, 10-layer facility for theoretical (red), simulation (green), and experimental (blue) indoor wheat growing scenarios (as shown in Fig. 2 and SI Appendix, Table S4), assuming wheat prices of $200/t in 2019 (2) and $500/t and $800/t in 2050 (based on a likely increase in the future price and premium price for pesticide-free production). The 2050 cost is the same for the $500/t and $800/t wheat price scenarios. Data point labels are cost/return ratios for each scenario. Error bars show SEM when larger than symbols.