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Reorienting Waste Remediation Towards Harnessing Bioenergy 259

CH O
3 CH CH O CH O CH CH O
2 3 3 2 3
n n
O O n
O O
PHB PHV PHBV
Figure 6.7 General structure of bioplastics.

with structural properties and processability similar to that for conventional
plastics (Lee, 1996).

6.5.2 Bioplastics Production from Wastewater and CO 2
The development of pure culture fermentation and the commercialization
of PHAs increases the cost of bioplastics to about four to nine times higher
than that of conventional plastics (Moita and Lemos, 2012). To overcome
this problem, considerable effort has gone into the production of PHAs
using mixed cultures and wastewaters such as olive oil mill effluent
(Beccari et al., 2009), sugarcane molasses (Albuquerque et al., 2011; Bengts-
son et al., 2010), distillery spent wash (Amulya et al., 2014; Khardenavis
et al., 2007), paper mill wastewater (Bengtsson et al., 2008), tomato cannery
wastewater (Liu et al., 2008), designed synthetic wastewater (Srikanth et al.,
2012; Venkata Mohan and Venkateswar Reddy, 2013; Venkateswar Reddy
and Venkata Mohan, 2012a), food waste (Venkateswar Reddy and Venkata
Mohan, 2012b), pyrolysis by-products (Moita and Lemos, 2011), pea shells
(Patel et al., 2012). Integrating PHA production with biohydrogen reactor
effluents is also being pursued as it offers the dual benefit of PHA recovery
and enhanced waste treatment (Venkateswar Reddy et al., 2013; Amulya
et al 2014., Venkata Mohan et al., 2010c; Venkateswar Reddy et al., 2012a,
b). The advantages of mixed culture approaches are the use of a cheap carbon
source and lower equipment cost (Salehizadeh and Van Loosdrecht, 2004).
Disadvantages include low product yields, impurity of the produced PHA,
and high PHA recovery costs. Furthermore, the use of open mixed cultures,
such as activated sludge, has been developed by employing anaerobic condi-
tions (17% DCW), aerobic conditions (36% DCW), and microaerophilic-
aerobic process (oxygen limitation) (62% DCW) for the production of
PHA. Rhodospirillum rubrum, a purple nonsulfur photosynthetic bacterium is
capable of producing PHA when fed with CO 2 as a substrate. PHA can be
extracted from bacterial cells and used as a biodegradable plastic with material
properties similar to those of polypropylene (Choi et al., 2010). The PHA