NASA is cultivating renewable energy?

You may wonder what's the relationship between NASA and renewable energy.
In fact, according to Jonathan Trent, the lead scientist at NASA Ames Research Center, " we are not passengers on spaceship Earth, we are the crew." Imagine we are astronauts going into space towards Mars, where will take at least 3 years to reach. And we have to bring life necessities and manage to use resources in a more sustainable way to accomplish missions and, most of all, survive. Living in a resources-limited Earth is much the same scenario as in a spaceship, which is what inspired NASA's "Sustainable Energy for Spaceship Earth" project.  Among this project, producing biofuels from algae has become main interest. Why? Economics. Last blog, I mentioned some second-generation biomass like Switchgrass which can yield 500 GJ/ha/yr (≒240 Gcal/acre-yr). While some microalgae can produce over 5000 Gcal/acre-yr, that is, 2,000 gallons of oil per acre per year. You can easily make a comparison of microalgae with other biomass from the following figure.

Source: TEDxSanJoseCA -Jonathan Trent, PhD - Can We Cultivate Energy?

Although two pilot land-based methods, open ponds and closed bioreactors, have been used to grow freshwater algae, there are some inevitable freshwater and land resources problems. Growing algae in open ponds needs sustainable water supply to prevent evaporation influencing steady growth conditions. While in closed bioreactors, evaporation won't be a disturbance, yet the computer-monitored systems are extremely expensive.

Bioreactors. Source: NASA 

To overcome these obstacles, NASA scientists have developed an ingenious system, ' Offshore Membrane Enclosure for Growing Algae (OMEGA)'. OMEGA is designed to commercially produce  carbon-neutral biofuel, yet it can at the same time clean waste water. In addition, cultivating algae in offshore doesn't compete with agriculture for land, freshwater or fertilizers. How does it achieve lots of advantages? Are there any potential effects on environments?

source: NASA

The idea is straightforward, nonetheless, state of the art techniques are needed. In OMEGA,  freshwater  algae are grown in semi-permeable membranes(plastic bags), filled with sewage providing growth nutrients. The algae can clean up the waste water while growing, meanwhile, clean water can pass  naturally into ocean via membranes (osmosis). The 'forward-osmosis membranes' can retain the algae and nutrients while release freshwater. In addition, algae absorbs carbon dioxide from the air and release oxygen after photosynthesis. Hence, biofuels produced from the algae are carbon-neutral, i.e. , the same amount of CO2 is fixed by the algae and burned using biofuels , no additional CO2 is released. These membranes also provide some marine habitats for aquaculture.

Now you may think what if this system is leaked and the algae is released to the ocean? According to Trent, OMEGA won't cause any environmental problems. The freshwater algae will either become a  part of food chains or die in the ocean.

Compared to the other land-based biomass, which consuming water and fertilizers and requiring land usage, OMEGA seems to be quite a solution to the resources depleting world.

References:
NASA OMEGA

TEDxSanJoseCA - Jonathan Trent, PhD- Can We Cultivate Energy?