148
Moreover, the majority of polyhydroxyalkanoate production studies have focused
on cradle-to-gate ignoring use and end of life disposal. Given that one major driver
for polyhydroxyalkanoates is its biodegradability, there is a need for analyses to
encompass this important aspect. However, to date marine biodiversity loss due to
plastic debris is a missing component from life cycle analysis methodology due to
lack of sufficient data on impacts, degradation, and transport/fate routes (Woods
et al. 2016). In contrast, end of life impacts for greenhouse gas emissions may not
be positive, with Hottle et al. (2013) demonstrating high GHGs associated with
methane emissions from disposal of biopolymers in landfills, for example. However,
end of life disposal of biopolymers is currently with a high degree of uncertainty,
and with appropriate end of life disposal routes such as anaerobic digestion or landfill with dedicated methane capture, the benefits should be positive.
Economics are another critical aspect to the sustainability and uptake of this
technology. Studies on industrial wastewater treatment coupled with polyhydroxyalkanoates place the cost of produced polyhydroxyalkanoates in the order of $2–3/
kg (Hassan et al. 1997; Gurieff and Lant 2007; Dacosta et al. 2015) which is significantly less than the current market prices for polyhydroxyalkanoates of approximately $5/kg (Kourmentza et al. 2017; Fradinho et al. 2014). Costs of production
appear most reliant on polyhydroxyalkanoates extraction due to the high cost of
solvents (Hassan et al. 1997; Dacosta et al. 2015). This aspect accounted for around
three quarters of the total production price in the study of Hassan et al. using a
photosynthetic-based open pond systems for treatment of palm oil mill effluent. The
same authors demonstrated that polyhydroxyalkanoates accumulation and size of
plant had relatively minor impacts on the production cost, although Gurieff and
Lant (2007) indicated plant size and substrate concentration were much more
important with their heterotrophic three-stage reactor system. However, economic
analyses to date have been based on laboratory and small pilot-scale studies, and
there is a need for costing and optimization based on data from development of fullscale systems that are not yet developed for microbial mixed cultures.
5.11 Conclusion
Polyhydroxyalkanoates are valuable biopolymer due to its ease of production from
a variety of feedstocks, its inherent biodegradability, as well as a variety of other
characteristics including UV resistance and limited oxygen permeability. Under
increasing actions globally to mitigate climate change through reduced reliance on
fossil fuels and efforts to reduce environmental burdens of plastic waste, there is a
growing market for polyhydroxyalkanoates and other biopolymers. Correspondingly,
there is an increasing trend of viewing wastewater treatment plants as resource
recovery factories rather than simple pollution control facilities. These developments open up the opportunity for incorporation of polyhydroxyalkanoates production into existing industrial wastewater plants in order to recover the abundant
chemical energy present.
S. Sali and H. R. Mackey
Moreover, the majority of polyhydroxyalkanoate production studies have focused
on cradle-to-gate ignoring use and end of life disposal. Given that one major driver
for polyhydroxyalkanoates is its biodegradability, there is a need for analyses to
encompass this important aspect. However, to date marine biodiversity loss due to
plastic debris is a missing component from life cycle analysis methodology due to
lack of sufficient data on impacts, degradation, and transport/fate routes (Woods
et al. 2016). In contrast, end of life impacts for greenhouse gas emissions may not
be positive, with Hottle et al. (2013) demonstrating high GHGs associated with
methane emissions from disposal of biopolymers in landfills, for example. However,
end of life disposal of biopolymers is currently with a high degree of uncertainty,
and with appropriate end of life disposal routes such as anaerobic digestion or landfill with dedicated methane capture, the benefits should be positive.
Economics are another critical aspect to the sustainability and uptake of this
technology. Studies on industrial wastewater treatment coupled with polyhydroxyalkanoates place the cost of produced polyhydroxyalkanoates in the order of $2–3/
kg (Hassan et al. 1997; Gurieff and Lant 2007; Dacosta et al. 2015) which is significantly less than the current market prices for polyhydroxyalkanoates of approximately $5/kg (Kourmentza et al. 2017; Fradinho et al. 2014). Costs of production
appear most reliant on polyhydroxyalkanoates extraction due to the high cost of
solvents (Hassan et al. 1997; Dacosta et al. 2015). This aspect accounted for around
three quarters of the total production price in the study of Hassan et al. using a
photosynthetic-based open pond systems for treatment of palm oil mill effluent. The
same authors demonstrated that polyhydroxyalkanoates accumulation and size of
plant had relatively minor impacts on the production cost, although Gurieff and
Lant (2007) indicated plant size and substrate concentration were much more
important with their heterotrophic three-stage reactor system. However, economic
analyses to date have been based on laboratory and small pilot-scale studies, and
there is a need for costing and optimization based on data from development of fullscale systems that are not yet developed for microbial mixed cultures.
5.11 Conclusion
Polyhydroxyalkanoates are valuable biopolymer due to its ease of production from
a variety of feedstocks, its inherent biodegradability, as well as a variety of other
characteristics including UV resistance and limited oxygen permeability. Under
increasing actions globally to mitigate climate change through reduced reliance on
fossil fuels and efforts to reduce environmental burdens of plastic waste, there is a
growing market for polyhydroxyalkanoates and other biopolymers. Correspondingly,
there is an increasing trend of viewing wastewater treatment plants as resource
recovery factories rather than simple pollution control facilities. These developments open up the opportunity for incorporation of polyhydroxyalkanoates production into existing industrial wastewater plants in order to recover the abundant
chemical energy present.
S. Sali and H. R. Mackey