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Not Your Backyard Compost Heap
"Yuck!"
If that's how you feel when your garbage can overflows,
imagine what it's like for astronauts when they find
themselves with a lot of garbage and only a little room
to store it.
Researchers at NASA's Kennedy Space Center in Florida
are using biology to hunt for a way to reduce the amount
of space taken up by solid waste, primarily food waste.
They also want to extract nutrients that might be used
to grow plants in space. |
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Right: As part of routine
procedures, cosmonaut Yury V. Usachev, Expedition Two mission
commander, changes out a solid waste container in the Zvezda/Service
Module in 2001. Credit: NASA
"We want to regenerate and recycle as much as we can,"
said Dr. Richard Strayer, a microbial research scientist with
Dynamac at KSC. "The best system wouldn't take up much
space, power or crew time."
On the International Space Station, for example, solid waste
is stored in bags and containers until a Russian Progress
module arrives. Once the unmanned Progress is emptied of fresh
supplies, it is packed with trash and sent back to Earth,
where it is incinerated over the ocean during a controlled
re-entry.
There are other ways to manage waste in space, but none are
ideal. Burning uses valuable oxygen. Waste can be sterilized
or dehydrated until it can be disposed of, but if it ever
gets wet or comes into contact with germs, it will become
a problem again.
A few years ago, KSC scientists
participated in a study to see what Shuttle trash typically
is made of and to determine the amounts of its components.
The study allowed researchers to replicate the typical
waste load in order to improve the process.
Right: The Research
Space Bioconverter is a rotating drum (far left) containing
waste for decomposition. In the foreground is a control
panel; in the background is the computer monitor for
the data collection system.
Photo Credit: NASA/KSC |
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One of the methods in testing right now is the Research Space
Bioconverter (RSB), a composter consisting of a rotating drum
that contains waste for decomposition. Linked to a computerized
data collection system in KSC's Space Life Sciences Lab, it's
nothing like your backyard compost heap. Its goal is to find
an efficient way to break down waste while extracting as many
nutrients as possible.
Strayer's team uses a regular food processor to create mock
waste, or biomass, similar to what might be found on a spacecraft.
Inside a rotating metal bioreactor, a microbial brew is mixed
with the waste.
Microbes need oxygen to do their decomposition work, but
oxygen should be spent on the crew instead of waste. However,
composting anaerobically -- without oxygen -- can cause nasty
smells.
Fortunately, some organisms use nitrate instead of oxygen.
In the RSB, Strayer is experimenting with a process called
denitrification, in which organisms use nitrate instead of
oxygen to break down the waste and produce nitrogen as a byproduct.
This process, anaerobic respiration using nitrate, has never
been tried in composting and is achieving promising results.
The RSB is intended for use in microgravity. But waste management
in a low-gravity environment and on long duration missions
will become increasingly important as NASA prepares to send
humans to the Moon, and Mars and beyond as part of its vision
for exploration.
| So, the next time you take
out the garbage or toss a leftover sandwich into the
kitchen trash, be thankful it's that simple on Earth.
With research projects like the RSB underway, future
spacefarers may find it almost as easy.
Right: Shuttle trash
wrapped in plastic and duct tape, known as a "football,"
is not the best idea for long durations, such as on
the ISS.
Photo Credit: NASA
Anna Heiney
NASA's John F. Kennedy Space Center |
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