At this time of global need for sustainable fuels, the deployment of game-changing technologies is critical to economies and environments on a global scale. It is clear from this and other recent analyses focused on life cycles and energy balances (Stephens et al. 2010) that a very compelling case can be made for photosynthesis as a platform technology for renewable production of fuels. More specifically, an engineered cyanobacterial organism for direct continuous conversion of CO2 into

infrastructure-compatible, secreted fuel molecules surpasses the productivities of alternatives that rely on the growth of biomass for downstream conversion into product. Photon utilization assumptions The assumptions inherent in a calculation of overall efficiency of a photosynthetic process are based on areal insolation, capture, and conversion, and GANT61 clinical trial are analyzed relative to a sequentially accumulating loss of photons that are not gainfully selleck kinase inhibitor utilized for the production of product. When accounting for the ultimate contingent of photons that are converted, the loss at each process step is a percentage fraction of the total available from the previous step. The descriptions below follow the sequence of process conversion steps and reflect the

accumulating losses and resultant efficiencies illustrated in Fig. 2. Values described below are summarized in Table 3. PAR radiation fraction The analysis assumes that only the solar radiation reaching the ground is available for conversion and the cumulative loss is computed with Selleckchem Sepantronium respect to this boundary value. Although the average total solar radiation reaching the ground varies throughout the world, many we assume that the relative efficiency of each subsequent step in the conversion process is location-independent to a first-order approximation. The energy fraction of solar radiation reaching the ground

that lies in the PAR range does vary with location and time of day. Results obtained from NREL models (Gueymard 2005; Bird and Riordan 1984) indicate that the PAR radiation fraction ranges from about 47–50% in the southwest USA. For the calculations performed in this article, we use a value of 48.7% for PAR radiation fraction to remain consistent with Zhu et al. (2008), resulting in a loss of 51.3%. Culture growth In the direct process, once reactors are inoculated, cells must be grown up to high density before the production phase. Thereafter, the process is continuous for an extended period. Based on pilot experience, we assume an 8-week process time, 3 days of growth at doubling times ~3 h followed by 53 days of production with no biomass accumulation, before the reactors must be emptied and reinoculated. Direct production of a fungible product minimizes downstream processing. This results in a reactor availability loss of about 5%.