I am familiar with the diapers that service uses. They are Nature Baby Care. Nature Baby Care disposable diapers are made of greener materials but still contain, for example, SAP (the gel stuff that lets sposies absorb pee). And according to the Nature Baby Care website FAQs, their diapers are not 100% biodegradable, and are not suitable for home-composting (because home-composting cannot achieve temps high enough to kill the bacteria from human waste). In fact, they do not recommend composting their products at all, not even commercially (as presumably the service your friend is thinking of using would be). Also, the Nature Baby Care manufacturing process still uses some petrol-based materials, although they use less than say, Pampers does.
Sources:
http://www.naty.com/us/CustomerServi...9/Default.aspxhttp://www.earth-baby.com/summary.ph...s#2f1974b4d2ae
I guess bottom line is, I'm curious what your friend's motivations are. I don't think it's an especially bad choice if they don't mind spending so much money. I wouldn't have chosen it myself, because I chose cloth over sposies for my babies' skin, not for the earth, and although the Nature Baby care diapers seem to have less crap than Pampers, it still has the gel stuff which would have been concerning to me.