The other kind of open fermentation relies on two unique aspects of the open fermenter: easy access to oxygen in the air and the geometry of the fermenter itself. Brewer's yeast needs oxygen for its activities and having an ample supply nearby can help yeast do its job. As for the shape, tank geometry actually impacts yeast performance. In the case of our open fermenter, that shape (short and wide) induces yeast to produce a fruitier profile in the beer.
After reading about both kinds of fermentation, you're probably saying "well, why wouldn't all those wild strains of yeast and bacteria still get in and affect the beer in the second style of open fermentation?" The reality is that with an open fermentation utilizing brewer's yeast there is always the threat of contamination from outside microbes. Typically, however, brewer's yeast starts doing its job so quickly and vigorously that enough CO2 is being produced to push away any airborne microbes that might be nearby, effectively creating a buffer zone against outside contaminants. Additionally, once fermentation slows down (and, with that, a large decline in CO2 production), the beer is transferred to a closed fermenter.
At Lost Rhino, we utilize the second kind of open fermentation. There are a number of beers we produce in our open fermenter. In terms of regularly available beers, both our kölsch and hefeweizen are fermented in the open fermenter. In addition, we have produced both 2200 lbs of Sin (our barley wine) and Woody Stout in our open fermenter. If you're interested in trying any of these beers out, both our kölsch and hefeweizen are on draft in our tasting room, and Woody Stout is on its way there in the coming weeks.