Well, considering that chaff accumulated over the five or so years I have been using the roaster, it could be from any number of bean types. I almost exclusively roast Ehtiopian beans at the moment (mostly Sidamo, some Yirgacheffe), but have roasted beans from Sumatra, Costa Rica, Mexico, Honduras, Brazil, Guatemala, Kenya, Nicaragua, Tanzania... possibly others I've forgotten. But Sidamo is my favourite.