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.
Source:nasa.gov |
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Disposable plastic bags filled with sewerage, use algae to remove carbon dioxide
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