In this analysis, the engineered cyanobacterial system is one engineered with a pathway for linear saturated alkane synthesis (Reppas and Ridley 2010) and an alkane secretion module, and with a mechanism to control carbon partitioning to either cell growth or alkane production. Comparison of efficiencies for an algal pond biomass-to-biodiesel and a cyanobacterial direct-to-fungible diesel process For comparison, we present two process scenarios and a theoretical maximum and compute

find more practical maximum efficiencies. To use the empirically determined surface insolation rates of NREL, each scenario assumes a common location, e.g., Phoenix, AZ, and the energy input begins with the boundary of photons incident on a horizontal surface

at that locale, e.g., 7,300 MJ/m2/year. We Selleckchem NU7441 compare the accumulation of energy losses at each process step and the resultant input for conversion by the organism. The factors that lead to photon loss are based on empirical measurements and on literature reports (see particularly Weyer et al. 2009; Zhu et al. 2008; also Benemann and selleck products Oswald 1994; Chisti 2007; Gordon and Polle 2007; Dismukes et al. 2008; Rosenberg et al. 2008; Schenk et al. 2008; Angermayr et al. 2009; Stephens et al. 2010; Wijffels and Barbosa 2010; Zemke et al. 2010; Zijffers et al. 2010), and are described in photon utilization assumptions (below). Note that some loss categories are defined differently by different authors but we have attempted to account for all basic assumptions in our comparative analysis. The direct scenario assumes conversion of fixed CO2 directly to a hydrocarbon, while minimizing production of biomass, and further involves secretion and continuous capture of the hydrocarbon product from the culture medium during a defined process interval. This scenario is designed for efficient capture and conversion of solar radiation in

a densely arrayed closed reactor format. The theoretical SB-3CT maximum scenario does not include the losses associated with culture growth, surface reflection, photon utilization, photorespiration, mitochondrial respiration, process cycling, and nonfuel production, (Table 3). Table 3 Individual contributions to photon energy losses in algal open pond and direct process scenarios (see photon utilization assumptions for a description). Cumulative contributions are illustrated in Fig. 2 Energy loss factor Algal open pond (%) Direct, continuous (%) Direct theoretical maximum (%) Unusable radiation (non-PAR fraction) 51.3 51.3 51.3 Culture growth loss 20 5.4 0 Reactor surface reflection loss 2 15 0 Culture reflection loss 10 10 10 Photon utilization loss 15 15 0 Photosynthetic metabolic loss 70.2 74.8 70.