Potential utilization of guar straw and wood wool in controlling relative humidity and temperature of storage environment

In this study, guar straw and wood wool were used for the development of a relative humidity (RH) and temperature control system based on the storage requirement of onions in a semi-arid region. The RH and temperature control system includes two major units: (a) dehumidification-three compartments of guar straw balls/guar balls and (b) humidification-water-saturated wood wool pad (evaporative cooling). Guar balls of similar to 25 mm diameter were made by mixing 40% straw powder, 59.5% water, and 0.5% guar gum (wt/wt). The balls were dried until 5.6% moisture level before using in dehumidification unit and analyzed for thermal properties. The RH and temperature control system was evaluated for its ability to maintain the requisite RH inside the onion storage structure. The dehumidification unit can reduce the RH by 4.9% and the humidification unit can increase the RH by 4.2% in the storage chamber. Further, the humidification unit has a cooling efficiency of 83.3%. The control system was efficient in maintaining the necessary storage RH in a range of 60-70% with a variation of 1.5%, and 22-37 degrees C storage temperature. Therefore, the storability of the onions in the conditioned environment was close to five months compared to three and a half months in control/ambient condition. Overall, the novel guar straw balls showed the desiccant properties that can be used with water-saturated wood wool for controlling RH and temperature of a storage environment. Practical Applications Agricultural waste generally remains unutilized that create disposal and environmental challenges. Hence, the task of agricultural waste management is paramount. For farm and industrial applications, the development of low-cost desiccants and systems for controlling conditioned atmosphere using agricultural waste is interesting. In the present study, a relative humidity (RH) and temperature control system was developed using guar straw and wood wool. The control system is proved to be efficient in maintaining the storage requirement of onions; thus, extended the storage life significantly. This environmental-friendly system can be used, in storage, preservation and drying of food products.