Fig. 4
From: Microwave-assisted organic acids and green hydrogen production during mixed culture fermentation
A Graphical representation of statistical significance (significant for p < 0.05) of group comparisons for hydrogen and total gas volumes, hydrogen formation efficiency and hydrogen fraction. The marker in the grey area indicates a significant difference between the respective comparison groups. B Production of volatile fatty acids (median) differentiated by treatment method and feeding amount. Volatile fatty acids were analysed in triplicate in all cases. C Course of gas production over seven days and D first 24 h for untreated (control) and heat-shock-treated (oven and microwave) experiments. Performed with sewage sludge and 75 g/l sucrose as feeding substrate