An ASL reactor consists of an acidification reactor and a methanogenicreactor. The schematic of the bioreactor is shown in Figure 2. Three runs of experiments (Runs A, B and C) were conducted at 35, 45, 50, 55 and 60°C. The acidifi cation reactors have an inner diameter of 140 mm and a total effective volume of 5 L, while the methanogenic reactor has a working volume of 3 L.