Besides, many kinds of organic effluents or wastes (i.e., olive mill effluent, sugar cane molasses, paper mill wastewater and food waste) can be used as renewable carbon sources (Albuquerque et al., 2010; Bengtsson et al., 2008; Dionisi et al., 2005; Venkateswar Reddy and Venkata Mohan, 2012).
The combined use of mixed microbes and waste carbon allows energy saving (no sterilization is required) and material cost reduction.