Production of liquid fuels and chemicals by microalgae. Final subcontract report

An overall objective of the project was to conceptually determine if simple open pond systems have application for the production of fuels from microalgae. To demonstrate the overall objective, work concentrated on showing the potential microalgal yields that are possible from an open pond system on a sustained basis. Furthermore, problems associated with this experimental system were documented and reported so that future endeavors shall benefit. Finally, operational costs were documented to permit preliminary economic analysis of the system. The major conclusions of this project can be summarized as follows: (1) Using two wildtype species in northern California a yearly average productivity of 15 gm/m/sup 2//day, or 24 tons/acre/yr can be obtained in water with TDS = 4 to 8 ppt. (2) This can probably be increased to 20 to 25 gm/m/sup 2//day or 32 to 40 tons/acre/y in southern California. (3) Productivity can probably be further increased by using competitive strains screened for low respiration rates, tolerances to high levels of dissolved oxygen, broad temperature optima, and resistance to photoinhibition. (4) In systems with randomized, turbulent mixing, productivity is independent of channel velocity at least for productivities up to 25 to 30 gm/m/sup 2//day and velocities from 1 tomore » 30 cm/sec. (5) Storage product induction requires one to three days of growth in batch mode under n-depleted conditions. (6) Critical cost centers include CO/sub 2/ input, harvesting and system capital cost. (7) Media recycling, necessary for water conservation, has no adverse effects, at least in the short term for strains which do not excrete organics, and when the harvesting method is at least moderately effective for all algal forms which may be present. 8 refs., 28 figs., 56 tabs.« less