Life cycle assessment and economic analysis of bioplastics production from cyanobacteria

Abstract

Cyanobacteria are interesting microorganisms to produce polyhydroxybutyrate (PHB), a biodegradable plastic similar to polypropylene. In this study, a Life Cycle Assessment and an economic analysis were carried out to assess the sustainability of the process. Different scenarios were analysed including different nutrient sources (i.e. wastewater and standard growth medium BG-11) and different PHB contents (from 15%dcw to 35%dcw and 50%dcw). Regarding the environmental impacts, increasing the PHB content drastically reduced (between 67 and 75%) the environmental impacts of the process. Environmental impacts were mainly caused by construction materials and the use of chemicals (especially chloroform for PHB purification). The economic analysis showed that the minimum selling price was 135 € kgPHB−1 (PHB content: 50%dcw; productivity: 12.5 gPHB m−3 d−1). A PHB productivity of 810 mg L−1 d−1 would be necessary to obtain a PHB selling price of 4 € kgPHB−1 (i.e. PHB market price). To reach this productivity it would be necessary to improve the reactor design (lower Volume:Surface ratio) and modify the strains genetically.