This article from CNN highlights an invention by Lynn Mueller which captures heat from sewage (sewage heat reclamation):

CNN: Clean energy gets dirty: Turning sewage into heat
by Jackie Wattles, CNN Money, May 24, 2016

Based in Vancouver, Lynn and International Water Systems now have a backlog of projects from around the world for the “Sharc” technology.  The system uses energy to power a heat pump, however, every $1 used to power the Sharq heat pump system produces $4.50 worth of energy.

And no, Lynn Mueller — the inventor of the sewage-to-heat technology — is not related to Martin or I. 🙂