BPs need to be kept in a warm, humid environment, and bacteria and other nasties can breed pretty quickly. You need a substrate that you change out entirely, so that the bacteria don't build up.

You MIGHT be ok if you have at least twice as much towel as you need, and THOROUGHLY clean and disinfect the dirty one each time you change it out. But I do not advise it.

Newspaper or paper towel works very well, you simply discard it and use new as soon as it gets soiled. People also use aspen or cypress mulch, by spot cleaning it as needed and changing it out entirely at certain intervals.