Schematic comparison between algal biomass and direct photosynthetic processes. The direct process, developed by Joule and called Helioculture™, combines an engineered cyanobacterial organism supplemented with a product pathway and secretion system to produce and secrete a fungible alkane diesel product continuously in a SolarConverter™ designed to efficiently and economically collect and convert photonic energy. The process is closed and uses industrial waste CO2 at concentrations 50–100× higher than atmospheric. The organism is further engineered to provide a switchable control between carbon partitioning for biomass or product. The algal process is based on growth of an oil-producing culture in an industrial pond on atmospheric CO2, biomass harvesting, oil extraction, and chemical esterification to produce a biodiesel ester
A new dawn for industrial photosynthesis by Dan E. Robertson, Stuart A. Jacobson, Frederick Morgan, David Berry, George M. Church and Noubar B. Afeyan
The conversion efficiency for the direct process is about seven times larger than that for an algal open pond.
The article, entitled “A New Dawn for Industrial Photosynthesis,” quantitatively affirms the advantages of Joule’s direct conversion process as compared to the indirect production of fuel from biomass, including algae. Though both processes aim to convert solar energy into fuel, the latter method requires the costly culturing, harvesting and processing of algal biomass – a multi-step intermediate stage that Joule’s process avoids. Moreover, Joule’s process directly yields hydrocarbons that are fungible with existing diesel infrastructure, unlike the biodiesel product that is produced from algal oil.
* Based on empirical measurements, Joule can directly produce 15,000 gallons of diesel per acre annually, as compared to 3,000 gallons of biodiesel produced indirectly from algae.
* The solar-to-product conversion efficiency of Joule’s direct, continuous process for producing diesel, ethanol and chemicals is between 5 and 50X greater than any biomass-dependent process, and gains additional efficiencies by avoiding downstream refining.
* Joule’s combined advances in genome engineering, solar capture and bioprocessing result in photosynthetic conversion efficiency of more than 7% relative to available yearly solar energy striking the ground, many times greater than prior industry assumptions.
Several emerging technologies are aiming to meet renewable fuel standards, mitigate greenhouse gas emissions, and provide viable alternatives to fossil fuels. Direct conversion of solar energy into fungible liquid fuel is a particularly attractive option, though conversion of that energy on an industrial scale depends on the efficiency of its capture and conversion. Large-scale programs have been undertaken in the recent past that used solar energy to grow innately oil-producing algae for biomass processing to biodiesel fuel. These efforts were ultimately deemed to be uneconomical because the costs of culturing, harvesting, and processing of algal biomass were not balanced by the process efficiencies for solar photon capture and conversion. This analysis addresses solar capture and conversion efficiencies and introduces a unique systems approach, enabled by advances in strain engineering, photobioreactor design, and a process that contradicts prejudicial opinions about the viability of industrial photosynthesis. We calculate efficiencies for this direct, continuous solar process based on common boundary conditions, empirical measurements and validated assumptions wherein genetically engineered cyanobacteria convert industrially sourced, high-concentration CO2 into secreted, fungible hydrocarbon products in a continuous process. These innovations are projected to operate at areal productivities far exceeding those based on accumulation and refining of plant or algal biomass or on prior assumptions of photosynthetic productivity. This concept, currently enabled for production of ethanol and alkane diesel fuel molecules, and operating at pilot scale, establishes a new paradigm for high productivity manufacturing of nonfossil-derived fuels and chemicals.
Sum of individual contributions and accumulated photon losses for two fuel processes and a theoretical maximum for energy conversion. The losses are represented on a logarithmic scale and accumulated serially for the processes beginning with the percent of PAR in empirically measured solar ground insolation. Total practical conversion efficiency after accounting for losses is indicated by the green arrows