Demonstration of a fertilizer-based liquid desiccant prototype for controlled plant environments

Healthy plant development and optimal crop yields require careful humidity control in closed plant environments. Recently, fertilizer solution has been proposed as an energy efficient liquid desiccant for greenhouse and plant environment applications. Here, we report the first demonstration of fertilizer-based solution being used to effectively control the humidity of a real and dynamic closed plant environment. This is done using a laboratory scale plant chamber and a liquid desiccant system with membrane contactors. Calcium nitrate solution is selected as a sample fertilizer and circulated in place of concentrated liquid desiccant. Hydroponic arugula is cultivated in the plant chamber. In the absence of any active dehumidification, humidity of the plant environment is shown to quickly approach saturation. Using the proposed fertilizer-based desiccant, humidity of the plant environment is successfully maintained at a variety of setpoints including 60, 70, and 80 % relative humidity with dehumidification rates reaching up to 0.76 ± 0.1 g/h. Testing is conducted under various conditions, including over all stages of the plant growth cycle from germination to maturity, and stable humidity is confirmed throughout. Although not fully automated and integrated, these findings support the notion that fertilizer-based desiccant systems can be scaled and integrated for dehumidification and fertigation of controlled plant environments.