[Greenbuilding] How green is cellulose infill?

[Jefro]

My wife and I have been planning a post-and-beam strawbale house for 
about 10 years now, and we are finally in escrow on property with the 
intention of building said house.  However, it seems that the cards are 
stacked against us for a variety of reasons, and we are now considering 
a move to blown cellulose instead.

Our goals for "green" construction are, in order:  healthy materials, 
recycled/low embodied energy materials,
low cost.  (That last is part of the reason for possibly abandoning 
strawbale.)

My questions are:  what sort of chemicals are mixed into cellulose to 
make it fireproof?  Is it simply a set of inert borate compounds, or are 
there hardcore chemicals involved?  I imagine this might be specific to 
different applications and even locales.  We are in northern coastal 
California.

Any advice is helpful!

thanks

Jeff