Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: "Waste" in Space
Date: Mon, 16 Aug 1999 22:53:46 GMT

In article <7p9th0$9fc$1@epos.tesco.net>, John Cody <Sfjc@tesco.net> wrote:
>I remember reading in a sci-fi book recently about an 'SCWO unit' for
>disposing of solid waste in piloted spacecraft. What is this? Is it
>feasible?
>I've just checked my book, apparently it stands for
>'Super-Critical-Wet-Oxidation'.

Or SuperCritical Water Oxidation.  Water is pretty near the universal
solvent at room temperature.  Heat it to quite high temperatures, under
fairly high pressure so that it doesn't boil, and it gets, uh, more so.
Dissolve a bit of oxygen in it, and you have a fantastically corrosive
witches' brew that will vigorously attack almost anything.  Throw in just
about any organic substance you care to name, and out comes water, CO2,
nitrogen, and sterile ash (oxides of metals, mostly).  One of the bigger
practical problems, in fact, is making the equipment stand up to it.  The
other major problem is that it's pretty power-intensive, because of the
high temperature and high pressure.

It's pretty much the preferred way to recycle organic wastes -- kitchen
garbage, human wastes, etc. -- in designs for advanced closed-cycle
life-support systems.  I don't believe it has actually flown yet, because
of the combination of complexity and high power demand.
--
The good old days                   |  Henry Spencer   henry@spsystems.net
weren't.                            |      (aka henry@zoo.toronto.edu)