Yeah, like QuickTD said, it's a mixture of veggie oil, gasoline, and maybe some petro-diesel, and their secret ingredient, which is apparently Xylol. I wouldn't call any of them except veggie oil non-dangerous. In the summer time, maybe it'd be okay, but I wouldn't in mine. SVO is cheaper ($0 per gallon once you have modified the vehical to heat the fuel).
I personally use regular biodiesel (both soy and canola based) without any modification to my vehical -- yes, it is $3/gallon, but I have never had any issues with it (aside from clogging my fuel filter with dirt it cleaned out of my system when I first switched). I have also run SVO in vehicals -- you just have to get it to 160F or more before entering the injector pump in order to get the viscosity low enough (unless you have a mercedes with the in line pump -- people have run those on cold veggie oil without killing the IP)
Maybe it's just that I am an engineer, not a chemist, so I don't mind modifying the vehical to run SVO, and not have to deal with mixing chemicals, be they methoxide to make biodiesel, or gasoline to thin SVO.