Techno-Economic Analysis of Cyanobacterial PHB Bioplastic Production

Poly-hydroxy-butyrate (PHB) is a promising bioplastic compound which is produced by photosynthetic cyanobacteria. Cyanobacterial PHB production has the potential to reduce traditional PHB production costs through using atmospheric CO₂ as a carbon substrate, as opposed to using expensive organic carbon substrates. This techno-economic analysis explores the financial profitability of using open raceway ponds to cultivate the cyanobacteria and solvent extraction on biomass to produce 10,000 tonnes of PHB per year. With a 10% PHB yield used, the capital cost for the plant was $193.5M USD and the operating cost was $147.3M USD per year. At $4,000 per tonne for PHB, the revenue of this plant was only $40M USD per year, resulting in a 20-year Net Present Value (NPV) of -$1.8B USD. The breakeven minimum PHB selling price (for a zero 20-year NPV) was $18,339 USD per tonne. The key driver behind profitability of cyanobacterial PHB production is PHB yield. Lastly, seven different hypothetical scenarios are explored to increase the economic viability of the cyanobacterial production. These strategies ranged from additional revenue streams from pigment extraction, treatment of wastewater, to decreasing capital costs by using deep ‘PHB ripening ponds’. Operational costs were reduced with flocculants, solar power purchase agreements and an on-site anaerobic digester to reduce both energy and nutrient costs through digestate use as pond media. The optimistic combination of all these factors resulted in a final minimum PHB selling price of $7,704 USD per tonne; still roughly twice the current market value of PHB.