Growth modeling to evaluate alternative cultivation strategies to enhance national microalgal biomass production

Abstract

We present a model-based assessment of alternative cultivation strategies for open pond algal biomass production within the conterminous United States (CONUS). Our assessment focuses on two basic cultivation strategies: (1) seasonal rotation of three representative freshwater algal strains that are well suited for warm weather, cold weather, and all-season diverse weather conditions, respectively; and (2) variation between three pond water depths (15 cm, 20 cm, and 25 cm). The enhanced Biomass Assessment Tool (BAT) is applied on a site-specific, hourly basis at 5832 North American Land Data Assimilation System Phase 2 1/8° meteorological model grid cells over a 30-year period (1980–2009) to evaluate the operational strategies. Recognizing that resource management decisions may also consider scales beyond the individual site, we also conduct a regional assessment focused on seven representative climate zones in the CONUS. Results demonstrate that the spatial variability of algal productivity is largely affected by the strain-specific growth response to light and temperature that vary significantly by climate zone and latitude. With a limited set of alternative cultivation strategies, the BAT identified the best-performing combination of cultivation strategies on a site-specific basis that considerably enhances national annual biomass productivity. In particular, the appropriate choice of seasonal strain rotation can significantly dampen climate-driven seasonal and spatial variability in algal productivity over the CONUS.