Cob: cob bench heater

[Louis]

Does anyone know about the efficacy of this cob bench heater?  This showed 
up on the essa list as being a downdraft design made from a barrel.  I 
wonder if it would be a less costly alternative to a true masonry 
heater.  How well does cob hold up with really high temperatures?  This is 
something I've been a little skeptical of.
Louis

http://www.proaxis.com/~deatech/cobcottage/pics/michael.jpg