Impact of strain, process, and site selection on the present and future success of the algae biofuel industry in the coterminous United States

E.R. Venteris, R. Skaggs, M.S. Wigmosta, A.M. Coleman
Pacific Northwest National Laboratory, US

Keywords: biofuel, algae, energy, biosource

Summary:

PNNL’s Biomass Assessment Tool (BAT) provides a national-scale, integrated modeling environment to study the complex interactions between algal biology, biomass to biofuel technology, and resource availability and costs. BAT enables detailed and rigorous incorporation of spatiotemporal variability information into site selection exercises and in estimates of national production potential, with a current focus on open-pond cultivation. In this presentation we analyze the relative import of economic and technical barriers between the three major aspects of production. Our current growth model simulates the effect of climate on strain performance in otherwise optimal water chemistry, nutrient, and ecological conditions. Within the coterminous United States (CONUS) and the limited set of algae species we can model, both climate (location) and strain selection are roughly equal in importance, with informed selections resulting in an 84% gain in biomass production. In addition, we have compared the production potential between lipid extraction and hydrothermal liquefaction (HTL) and found dramatic differences, with HTL potentially producing roughly 60% more renewable diesel for a given amount of biomass. The efficiency of HTL results in dramatic reductions in land, nutrient, and water consumption. In addition, we have investigated the spatial variability in availability and costs for a range of upstream and downstream resources including pond make up water (freshwater, saline/ brackish groundwater, and seawater), saline concentrate disposal, flue gas CO2 delivery, site leveling, land acquisition, infrastructure (connecting roads, electricity, natural gas and product pipelines), and transportation of nutrients to the site and fuel precursors (extracted lipids, HTL oil) to the nearest existing refinery. Whereas all add costs, we find that water supplies, providing CO2 through flue gas, and site constructability (leveling and avoidance of pond liner costs) impose the most significant impacts to the siting of cultivation facilities. Careful analysis and decision making based on each of the three main aspects of algae biofuel production is essential to maximize both economic efficiency and achieving energy scale production targets. Our current analyses demonstrate that at least 5 billion gallons yr-1 of production are likely attainable, with the ultimate production potential in the CONUS remaining highly uncertain.