The following is not direct criticism, as I have used butter to make refried beans and it is easily available - but, butter should be the low down the fat choice list as it has a strong flavor that competes with the beans. The first and most obvious/traditional fat to use is pig lard, but a neutral oil or shortening works perfectly well, too. My grandmother would use saved, rendered bacon fat from a Folgers coffee can she kept near the stove (because she always had bacon fat, grandaddy had to have bacon for every breakfast). I have also used olive oil, but only if making black beans (which can stand up to the flavor). Avocado oil works well, too.