James,
You may already know her but you might visit with Gayatri Datar at EarthEnable (gayatri@earthenable.org) there in Rwanda. We have discussed the surprisingly large carbon implications of EarthEnable earthen flooring a few times. We are working on the development of an ASTM standard to render earthen floors a more palatable and reliable low-carbon alternative.
cmd
C. Michael Donoghue, PE
Maritech Engineering, Inc.
Austin, Texas, USA