Washington DC
鈥淚鈥橫 TRYING as hard as I can, Captain,鈥� exclaims Scotty, the strain etching
lines in his forehead. 鈥淚 can鈥檛 give you any more!鈥� But unlike Star
Trek鈥檚 Enterprise, future spacecraft might use a less savoury energy supply
than Scotty鈥檚 beloved dilithium crystals: human waste.
NASA is enlisting the aid of Advanced Fuel Research of Connecticut in a new
$600 000 project to turn astronaut waste into a power source for
spaceships. The process might also yield other useful chemicals that are in
short supply aboard an interplanetary spacecraft or on an extraterrestrial base.
The secret is pyrolysis: breaking down the waste by heating it in the absence of
oxygen.
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Normally when you burn organic molecules such as those found in faeces or in
plastic, they combine with oxygen in the air, producing carbon dioxide and
water. But in pyrolysis, there is no oxygen to combine with, so the molecules
break their bonds and rearrange themselves into smaller molecules. 鈥淭hings start
breaking down at about 350 掳C, and what you start making includes a lot of
liquids,鈥� says AFR scientist Mike Serio. 鈥淎t 600 掳C or 650 掳C, you break
down the liquids into gases. It does give you flexibility.鈥�
You could burn these liquids or gases to release energy, or turn them into
plastics or other organic materials, says Jim Markham, the company鈥檚 chief
executive officer.
鈥淸Pyrolysis] can produce heavier molecules such as benzene or toluene, and
can be a source of raw materials to make plastics or rubber,鈥� says John Fisher,
a chemical engineer at NASA鈥檚 Ames Research Center in California. And pyrolysis
would also create ammonia for fertiliser.
Since the pyrolytic process works on many different organic compounds, it
will consume many types of fuel. 鈥淵ou can use human waste as well as other
waste, like scrap plastic bags,鈥� says Markham. And you don鈥檛 have to worry about
variations in the consistency and content of the waste material, the pyrolysis
unit should be able to handle them all. 鈥淚t鈥檚 tailored to unpredictable
mixtures,鈥� he says. 鈥淚deally, you鈥檇 dial in the desired outcome and it would
肠辞尘辫别苍蝉补迟别.鈥�
Though a Mars base is still a pipe dream, there might be a use for the
process back on Earth鈥攋ust dump your plastic or other organic waste in a
home pyrolysis unit and reap the energy. But in the meantime, Scotty will have
to continue milking his dilithium crystals.
This latest idea follows in the wake of a Russian project, announced last
year, which aims to use equally bizarre methods of recycling waste in order to
maximise available power. The Russian plan, intended to be ready for their first
crewed interplanetary mission, is to employ bacteria to break down the
astronauts鈥� used underwear to make additional methane, which could then be used
to power the spacecraft (快猫短视频, 12 December 1998, p 5).