ST3-07: Techno-economic analysis of microalgae-derived fuel production

It is well-established that microalgal-derived biofuels have the potential to make a significant contribution to the US fuel market, due to several unique characteristics inherent to algae.  However, there is a wide lack of public agreement on the near-term economic viability of algal biofuels, due to uncertainties and speculation on process scale-up associated with the nascent stage of the algal biofuel industry.  The present study aims to establish baseline economics for two microalgae pathways, by performing a comprehensive analysis using a set of assumptions for what can plausibly be achieved within a five-year timeframe.  Specifically, autotrophic production (utilizing CO₂ as the carbon source) via both open-pond and closed photobioreactor (PBR) systems is considered.  The production scale was set at 10 MMgal/yr of raw algal oil, subsequently upgraded to a green diesel blend stock via hydrotreating.  Rigorous mass balances were performed using Aspen Plus simulation software, and associated costs were evaluated on a unit-level basis.  Minimum product selling prices for lipid production were found to be $8.52/gal for open ponds and $18.10/gal for PBRs, while costs were fairly marginal to upgrade the algal oil to a diesel blend stock, at $9.84 and $20.53/gal of diesel for the respective cases.  Sensitivity analysis shows that while near-term costs are high, the economics have significant potential for future improvement, with costs strongly correlated primarily to lipid content, followed by algal growth rate.  Several key research areas were identified, and a resource assessment was also included to examine metrics such as land and water use.