Bioval makes the best Bio BB on the market, IMHO.
Other companies have entered into the BIO domain with mixed results, as an example G&G has thier own brand of Bio BB, glucose base, the will actualy start to break down in your hand if you hold them for to long. They are fine for a cold dry climate, but as soon as you play in a warm humid enviorment, forget it, you have a magazine full of sticky sweet gunk.
BIOVAL are a corn starch, potasium composite, depending on enviorment they have a deteriation rate of 30-90 days, harmless to the envierment, with no residue.
HIDD is also a good brand, thier stealth BB´s are pretty sweet, just an absolute pain in the backside when it comes to Hop-Up adjustments, Incredible difficult to track.