Figure 1

Effect of different ammonium acetate concentrations on the pH value of the anaerobic digestion (AD). The different amount of ammonium acetate was supplemented at L group (black square), M group (red circle symbol), H group (blue triangle symbol) and blank sample (violet triangle symbol). The experiments were operated in a 1 L fermentor at a mesophilic temperature of 37 ± 1°C for the semi-continuous AD.