Evaluating soda-lime adsorption and microcontroller-based system for the dynamic control of CO2 in a fresh produce storage box under varying temperature

Abstract

Effective storage of fresh produce requires precise control of temperature, O₂, CO₂, and relative humidity. The storage system with an air exchange to control O₂ has already been developed. In this study, a soda-lime reactor was introduced into the developed storage system for CO₂ control. Initially, the kinetics of CO₂ adsorption by soda-lime was studied at different temperatures (5, 10 and 20 °C) and relative humidity (>85 %). Then, the new system was integrated into a storage box containing 16 kg of broccoli and the performance evaluation was conducted under varying temperatures from 5 to 23 °C over a 120-h storage period. The analysis of soda-lime adsorption using the Weibull function showed an adsorption capacity of 267 L kg⁻¹. Adsorption was triggered at relative humidity above 80 %, highlighting its suitability for high-humidity conditions in fresh produce storage. While temperature affected the adsorption rate of soda-lime, it did not impact the overall capacity. During the entire storage period, CO₂ and O₂ concentrations inside the box were successfully maintained at 4 ± 2 % and 2 ± 1 %, respectively, even under varying temperatures. This approach highlights the potential of air exchange and soda-lime-based system as an alternative solution for the indirect control of O₂ as well as CO₂, using a simple temperature sensor and mathematical model.