Cob: cob/strawbale combo and devil grass questions

[artlady]

>From Arizona: Has devil grass rhizome/roots been tried as a straw 
substitute in cob houses? I've been hanging weeded grass on fences to 
dry it to death before composting it but it's hard to kill. If it has 
the right properties, could you use it fresh and expect it to die as the 
cob dries out?
When I move my compost and garden soil to my new land, I need to kill 
the "devil grass" roots without harming earth worms and friendly 
bacteria. We don't have "devil grass" out there and I don't want to 
introduce it. I was thinking of spreading batches of soil on tarps in 
the sun, what, maybe 2" thick but that may not kill it. Or I guess I 
could sift just the best compost, recompost it out there until I've 
weeded it out before introducing it into the garden area. Any 
suggestions on a faster/less labor intensive way?

I hope to do a strawbale/cob combination with the strawbale's insulative 
advantages on the shade side and because strawbale might be faster to 
construct.  Any advice on connecting them to each other and the roof?  I 
can't decide on the best roof. I have yet to attend workshops described 
on my website for Vaulted Straw Bale, but I love the sample photo with 
it's cob front: http://www.imagegypsy.com/sbvault.htm
Sandy Rice