CELSS research

>
> Why tie yourself down to using composting?

CEC -- Cation Exchange Capacity

Lunar regolith is not soil, and Martian soil is about the worst kind.
What both of these lack is the ability to hold onto nutrients such as
K+ and Ca++. This ability is called Cation Exchange Capacity or CEC.
The soil materials with the highest CEC are clay and humus. Clay is
heavy to transport and difficult to make. Humus, OTOH, are the
complex organic molecules which are very difficult for bacteria to
break down, so they are what's left after a thorough composting process.

If you use a pure hydroponic setup, CEC is not necessary, but it does
add a great deal of stability to the system by acting as a buffer for
nutrients.

>[snip] I don't know which one will ultimately be "better", and it may
be that one is better in one situation (e.g., composting on the
energy-poor surface of Mars) and another in another situation (e.g.,
wet oxidation in an energy-rich orbital habitat).<

I'm sure that some combination will work better than either
exclusively. I favor an approach of fast oxidation for potentially
infectious materials and composting for other organic wastes.

> I also have a request. Could you please say "**CONTROLLED**
Ecological Life Support Systems instead of "Closed Ecological...",
and moderate the "100% recycling and resource reclamation" goal?<

By the time we start sending ships to other stars, I expect getting as
close to 100% as possible will payback greatly in fuel saved. Also,
Biosphere2 had a goal of exchanging the inside air only once every 100
years but actually only managed to keep it to once a day. I think it
behooves us to set the ultimate goals for research high with the
understanding that intermediate goals will need to be reached first.
Thus, the "closed ecology" is the goal which we strive for with our
"controlled environments".

++JohnWheeler

P.S. I seriously doubt Terry is actually reading this message, as he