Production of PHAs from Microalgae

Biodegradable polymers are becoming an attractive alternative to traditional petroleum-based polymers; namely, polyhydroxyalkanoates (PHAs) are naturally occurring biodegradable polyesters synthesized by various microorganisms and are one of the most promising sustainable plastic alternatives in the market. PHAs can be produced naturally by bacteria or algae without diverting crops and can biodegrade in landfills or even marine environments. This project produces PHAs from the microalgal species Scenedesmus, employing the use of flat plate photobioreactors for algae cultivation, gravity settling and centrifugation for harvesting and dewatering, microbubble extraction for cell lysis, and a separation train for the purification of PHA from lipids. The annual production capacity is 8,367 US tons of PHAs, 29,283 US tons of de-oiled biomass, and 4,183 US tons of lipid (triolein), with the primary goal of achieving a 15% internal rate of return (IRR). However, with a total capital investment of $392.1 million and an annual profit margin of $19.3 million, this project fails to meet the desired economical outcome. The internal rate of return was 1.6% when using reasonable selling prices for the products but showed promise with a reduction of capital costs (e.g., reduction in algal photobioreactor costs) or an increase in the profit margins (e.g., increase in PHA selling price or reduction in utility usage).