Space

Converting human waste into rocket fuel

Converting human waste into ro...
Pratap Pullammanappallil poses with an anaerobic digester used in a process that turns human waste into rocket fuel (Photo: Amy Stuart, UF/IFAS Communications)
Pratap Pullammanappallil poses with an anaerobic digester used in a process that turns human waste into rocket fuel (Photo: Amy Stuart, UF/IFAS Communications)
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Pratap Pullammanappallil poses with an anaerobic digester used in a process that turns human waste into rocket fuel (Photo: Amy Stuart, UF/IFAS Communications)
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Pratap Pullammanappallil poses with an anaerobic digester used in a process that turns human waste into rocket fuel (Photo: Amy Stuart, UF/IFAS Communications)

Flushing the human waste produced on space missions out an airlock isn't an option for astronauts. Currently its stored in containers before being loaded into cargo vehicles that burn up as they pass through Earth's atmosphere, but researchers at the University of Florida (UF) have found a better use for the material, by developing a process to turn it into rocket fuel.

Over the years, there have been different proposals from various countries and private companies to build a base on the Moon. While we're still waiting for construction of such a base to begin, in 2006 NASA announced that it planned to have a permanently staffed base on the Moon by 2024 and began exploring ways to reduce the weight of spacecraft leaving the Earth.

Because carrying back stored waste from such long-term missions would be impractical, and dumping the waste on the Moon's surface being ruled out as an option, the space agency turned to UF researchers to come up with some alternative ideas. Pratap Pullammanappallil, a UF associate professor of agricultural and biological engineering and then-graduate student Abhishek Dhoble (now a doctoral student at the University of Illinois) took up the challenge.

NASA supplied the scientists with a packaged form of chemically produced human waste that also included simulated food waste, towels, wash cloths, clothing and packaging materials, and they ran tests to see how much and how fast methane could be produced from the materials.

Using an anaerobic digester process, in which microorganisms break down the organic material and kill pathogens in the absence of oxygen to produce a mixture of methane and carbon dioxide, they found were able to produce the equivalent of 290 L (77 gal) of methane per crew member per day over the period of a week.

"We were trying to find out how much methane can be produced from uneaten food, food packaging and human waste," said Pullammanappallil. "The idea was to see whether we could make enough fuel to launch rockets and not carry all the fuel and its weight from Earth for the return journey. Methane can be used to fuel the rockets. Enough methane can be produced to come back from the Moon."

Additionally, the digestion process would also produce around 757 L (200 gal) or non-potable water, which could then be split into hydrogen and oxygen through electrolysis. Pullammanappallil says the oxygen could be used in a back-up breathing system, while the exhaled carbon dioxide and hydrogen could be converted to methane and water in the process.

The researchers' study was published in the journal Advances in Space Research.

Source: University of Florida

7 comments
Mel Tisdale
"290 L (77 gal) of methane per crew member per day" Wow, and I thought I was pretty productive, if you catch my drift (not a nice experience some days!) No wonder they don't allow any naked flames on board. It must be something special about the astronauts' diet I suppose - or simply something to do with the pressure it is at. I wonder if it might be possible to adapt the average house to this process. If so, for a few pennies and a bit of plumbing work we could all go on diet and off grid with ease.
michael_dowling
Why can't they tweak the process,and make jet fuel from airline employee's contributions? The bigger the airline,the better!
Stephen N Russell
Love to see my poop go to rocket fuel Major sites for: India, Africa, SE Asia, alone Awesome. Mass produce
Gregg Eshelman
From now on, only Tex-Mex and Sichuan meals will be served in space.
Lamar Havard
Heck, me and Taco Bell have been doing that for years...
Slowburn
It would be better to then use the nutrient rich water to grow plants for food and air.
Riaanh
Why, oh why, cannot every sewage plant on earth become a power supplier instead of a power user?