Influence of Light Intensity and Spectrum on Duckweed Growth and Proteins in a Small-Scale, Re-Circulating Indoor Vertical Farm

Duckweeds can be potentially used in human and animal nutrition, biotechnology or wastewater treatment. To cultivate large quantities of a defined product quality, a standardized production process is needed. A small-scale, re-circulating indoor vertical farm (IVF) with artificial lighting and a nutrient control and dosing system was used for this purpose. The influence of different light intensities (50, 100 and 150 µmol m⁻² s⁻¹) and spectral distributions (red/blue ratios: 70/30, 50/50 and 30/70%) on relative growth rate (RGR), crude protein content (CPC), relative protein yield (RPY) and chlorophyll a of the duckweed species <i>Lemna minor</i> and <i>Wolffiella hyalina</i> were investigated. Increasing light intensity increased RGR (by 67% and 76%) and RPY (by 50% and 89%) and decreased chlorophyll a (by 27% and 32%) for <i>L. minor</i> and <i>W. hyalina</i>, respectively. The spectral distributions had no significant impact on any investigated parameter. <i>Wolffiella hyalina</i> achieved higher values in all investigated parameters compared to <i>L. minor</i>. This investigation proved the successful cultivation of duckweed in a small-scale, re-circulating IVF with artificial lighting.