.pwaste stands for permanent waste, or waste that can not be removed. It builds up slowly when regular waste is dumped. It cannot be removed and eventually will kill any bots such as Big Berthas. Permawaste is made during transfers of waste to other bots or though just having waste in the bot.
Permanent waste! Shudder!! This stuff is nasty. It builds up slowly. When I dump regular waste a little bit is left behind. I can never get rid of Permanent waste and eventually it WILL kill me. If you other robots don 't get me first.