Due to presence of numbers of impurities as
well as continuous increase in its global production (corresponding
to the increase in biodiesel production), the present market value
of CG is very low. According to a report by Yang et al. (2012), the
price of CG is only around $ 0.05/pound. Likewise, due to high
pH, high COD/BOD, presence of methanol as well as its viscous
nature, environmental disposal of CG is a challenge for biodiesel
manufacturers (Dobson et al., 2012). Alternatively, CG can be used
as a feedstock for microbial hydrogen production and in the context
of global interest for the development of renewable energy
sources, it can be considered as a promising technology.