we could use sewer flow to generate electricity both for day to day use and reserve,(reply>), I think most water companies have bio-digesters on site - periodically, they scoop up the solid waste trapped by filters and grids, and add them to the digester, which generates methane which helps provide at least a portion of the power the sewage plant uses. Meanwhile, the solid sludge produced is rich in nitrogen and phosphorus, so is often sold to farmers as an organic manure.,(reply>), Thames water uses the methane from sewage to power its sewage treatment plants,(reply>), That's a really crappy idea!,(reply>), @EscapeMCP<br>intresting. how practical is it?,(reply>), On the topic of utilizing sewage, there's a project somewhere where they are extracting stuff out of the sewage. I think it was mainly the valuable metals (Pt, Au, Ag).  Nice idea.