Ing Quimica

Bioresource Technology 98 (2007) 3393–3403

Comparative life cycle assessment and financial analysis of mixed culture polyhydroxyalkanoate production
Nicholas Gurieff, Paul Lant
*
Advanced Wastewater Management Centre, The University of Queensland, St. Lucia QLD 4072, Australia Received 16 June 2006; received in revised form 4 October 2006; accepted 22 October 2006 Available online 13 July2007

Abstract A life cycle assessment and financial analysis of mixed culture PHA (PHAMC) and biogas production was undertaken based on treating an industrial wastewater. Internal rate of return (IRR) and non-renewable CO2eq emissions were used to quantify financial viability and environmental impact. PHAMC was preferable to biogas production for treating the specified industrial effluent. PHAMC wasalso financially attractive in comparison to pure culture PHA production. Both PHA production processes had similar environmental impacts that were significantly lower than HDPE production. A large potential for optimisation exists for the PHAMC process as financial and environmental costs were primarily due to energy use for downstream processing. Under the conditions used in this work PHAMC was shownto be a viable biopolymer production process and an effective industrial wastewater treatment technology. This is the first study of its kind and provides valuable insight into the PHAMC process. Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Life cycle assessment; Polyhydroxyalkanoates; Mixed culture; Wastewater treatment

1. Introduction One of the most promising biodegradable materialsto emerge in recent times is the family of polyhydroxyalkanoate (PHA) polymers produced in almost all bacteria (Lee et al., 1999; Luengo et al., 2003; Reddy et al., 2003). Unlike other ‘degradable’ polymers such as those based on petrochemicals, poly-lactic acid (PLA) and starch polymers, PHAs naturally have useful properties and, therefore, do not need to sacrifice their true biodegradability forimproved properties. PHAs have properties similar to those of polyethylene and polypropylene (Holmes and Lim, 1990; Lee, 1996a) and the large number of copolymer blends that are possible allows for the potential to engineer polymers with the desired properties for a wide range of applications. The prevailing technology for PHA production is through the use of pure bacterial cultures utilising apure

*

Corresponding author. Tel.: +61 7 3365 4728; fax: +61 7 3365 4726. E-mail address: paul.lant@uq.edu.au (P. Lant).

concentrated substrate such as glucose. Although currently being produced commercially, the product is more expensive than available synthetic polymers and therefore is still mostly regarded as a fine rather than a commodity polymer. This has led to a number of studies(Byrom, 1987; Hassan et al., 1997; Lee and Choi, 1998; van Wegen et al., 1998; Choi and Lee, 1997, 1999a,b, 2000) that have aimed to optimise the economics of pure culture production, with a wide range of results that are highly dependent on the adopted assumptions and parameters. Mixed bacterial culture production has recently started to attract a lot of attention. It has the potential to producelarge amounts of PHAs with seemingly lower costs due to lower sterility, equipment and control requirements and the ability to utilise a wide range of cheap substrates including industrial and agricultural wastes (Reis et al., 2003; Rhu et al., 2003). The nature of mixed culture production from waste requires that this process competes financially with other polymer production processes (bothdegradable and non-degradable), and with other value-adding waste treatment processes that utilise the same waste resource, such as biogas production.

0960-8524/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2006.10.046

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N. Gurieff, P. Lant / Bioresource Technology 98 (2007) 3393–3403

Nomenclature HRT _ m O P Q r T V W WAa WAb b W X Y R g q...