Differentiation of the composting stages of green waste using the CIELAB color model

BACKGROUND: CIELAB color variables can be used to monitor a composting process and evaluate the maturity of the compost with a new, rapid, easy, and low-cost colorimetric analysis. However, to date there are no available data to support the ability of CIELAB color changes to depict the different stages of a composting procedure. This study aims to examine the correlation of CIELAB color variables with composting time to elucidate how color changes can be used to detect the different stages of a composting process. Two green waste industrial scale composting processes with different added materials were monitored using typical physicochemical and CIELAB color analyses. RESULTS: During composting, color variables a*, b*, C*, and Delta Epsilon* exhibited fluctuations following a constant variation trend that correlated with each composting phase. This behavior depicts the transformation of the organic composition of compost, as described by Organic Carbon (OC), Carbon-to-Nitrogen ratio (C/N), Humic Acids (HA), and Fulvic Acids (FA). Moreover, color variables a*, b*, and C* showed strong relationships with OC, C/N, and HA/FA (R-2 > 0.83) and with HA (R-2 > 0.74). These results indicate that CIELAB color change follows the same general pattern for each composting procedure that utilizes the same main composting substrate, regardless of any differing additional materials. CONCLUSION: Monitoring the CIELAB color variables made it possible to depict the different phases of composting, especially the transformation of the organic composition of the compost. Accurately monitoring CIELAB color variables distinguishes the different stages of a composting process through a rapid analysis at radically reduced costs compared to complex physicochemical analyses.(C) 2023 Society of Chemical Industry (SCI).