Various species of algae are known to produce valuable products ranging from food to fertilizer to biofuels. Methods have been developed for producing biofuels by processing algae and other micro-organisms that grow in aquatic environments, but the largescale commercial production of these algae, particularly for commodity products like biofuels, has been limited by the unfavorable economics of the current cultivation and harvesting methods.

A new cultivation and harvesting method was developed using flexible plastic photobioreactor (PBR) tubes with forward osmosis membranes. These PBRs are filled with nutrient-rich water (e.g., wastewater) and float in seawater. Forward osmosis, driven by the salt gradient between wastewater and the surrounding seawater, removes water and concentrates the algae for harvesting. The concentrated algae are processed, and the PBRs are cleaned and reused. The forward osmosis membranes also clean the water released into the seawater, which has a beneficial environmental impact.

This system is used in calm aquatic environments where the water provides infrastructural support through floatation and temperature regulation. The water motion from waves provides some mixing of the algae with the PBRs.

The size and plumbing of the PBRs in the overall system are critical to its function, which depends on light, temperature, and gas exchange. The forward osmosis membranes are used to remove water and concentrate the algae, and other types of semi-permeable membranes, such as gas-permeable and nutrient-permeable membranes, may also be incorporated. The different membranes influence the growth of algae, the harvesting, and the quality of water released into the environment.

This system was invented by Jonathan D. Trent and reduced to practice by (among others): Lance D. Delzeit, Michael T. Flynn, and Travis A. Liggett of Ames Research Center; Patrick Wiley and Brandi McKuen of the University of California at Merced; Tsegereda N. Embaye and Hiromi Kagawa of SETI Institute; and Sherwin J. Gormly, Patrick W. Buckwalter, and Robert Baertsch of National Space Grant Foundation. NASA invites companies to inquire about partnering opportunities and licensing this patented technology. Contact the Ames Technology Partnerships Office at 1-855-627-2249 or This email address is being protected from spambots. You need JavaScript enabled to view it.. Refer to ARC-16280-1.

NASA Tech Briefs Magazine

This article first appeared in the March, 2016 issue of NASA Tech Briefs Magazine.

Read more articles from this issue here.

Read more articles from the archives here.