Algae could give biofuels

NASA Envisions "Clean Energy" From Algae Grown in Waste Water

NASA scientists have proposed an ingenious and remarkably resourceful process to produce "clean energy" biofuels, that cleans waste water, removes carbon dioxide from the air, retains important nutrients, and does not compete with agriculture for land or freshwater.

Algae are similar to other plants in that they remove carbon dioxide from the atmosphere, produce oxygen as a by-product of photosynthesis, and use phosphates, nitrogen, and trace elements to grow and flourish. Unlike many plants, they produce fatty, lipid cells loaded with oil that can be used as fuel.

"The inspiration I had was to use offshore membrane enclosures to grow algae. We're going to deploy a large plastic bag in the ocean, and fill it with sewage. The algae use sewage to grow, and in the process of growing they clean up the sewage," said Jonathan Trent, the lead research scientist on the Spaceship Earth project at NASA Ames Research Center, Moffett Field, Cali.

It is a simple, but elegant concept. The bag will be made of semi-permeable membranes that allow fresh water to flow out into the ocean, while retaining the algae and nutrients. The membranes are called "forward-osmosis membranes." NASA is testing these membranes for recycling dirty water on future long-duration space missions. They are normal membranes that allow the water to run one way. With salt water on the outside and fresh water on the inside, the membrane prevents the salt from diluting the fresh water. It's a natural process, where large amounts of fresh water flow into the sea.

Floating on the ocean's surface, the inexpensive plastic bags will be collecting solar energy as the algae inside produce oxygen by photosynthesis. The algae will feed on the nutrients in the sewage, growing rich, fatty cells. Through osmosis, the bag will absorb carbon dioxide from the air, and release oxygen and fresh water. The temperature will be controlled by the heat capacity of the ocean, and the ocean's waves will keep the system mixed and active.

When the process is completed, biofuels will be made and sewage will be processed. For the first time, harmful sewage will no longer be dumped into the ocean. The algae and nutrients will be contained and collected in a bag. Not only will oil be produced, but nutrients will no longer be lost to the sea. According to Trent, the system ideally is fail proof. Even if the bag leaks, it won't contaminate the local environment. The enclosed fresh water algae will die in the ocean.

The bags are expected to last two years, and will be recycled afterwards. The plastic material may be used as plastic mulch, or possibly as a solid amendment in fields to retain moisture.

For full article read: http://www.nasa.gov/centers/ames/news/features/2009/clean_energy_042209.html