Chlorophyll changes during anaerobic digestion of cabbage waste

Abstract

ABSTRACT To study the changes in the contents of chlorophyll a and chlorophyll b in cabbage waste during anaerobic digestion, two types of leafy cabbage waste were treated by fermentation, and the relationship between the degradation of chlorophyll a and chlorophyll b in cabbage waste and gas production potential during anaerobic digestion was analyzed using an anaerobic batch fermentation unit maintained at a constant temperature of (35 ± 1) °C. The results showed that, following anaerobic digestion, the gas production rates of common cabbage, Chinese cabbage, and mixed cabbage were 36 mL/g, 33 mL/g, and 27 mL/g, respectively. The total solids (TS) gas production rates were 838 mL/g, 774 mL/g, and 549 mL/g, respectively, whereas the volatile solids (VS) gas production rates were 1061 mL/g, 1134 mL/g, and 636 mL/g. During the biogas fermentation process, the content of chlorophyll a in each type of cabbage waste was consistently higher than that of chlorophyll b. Moreover, chlorophyll degradation correlated with daily gas production. Among the cabbage waste types analyzed, mixed cabbage had the highest chlorophyll a and chlorophyll b degradation rates of 81.71% and 99.08%, respectively, compared to that of common cabbage or Chinese cabbage alone. These findings extend the current knowledge on anaerobic fermentation treatment of cabbage waste.