Researchers at the Newcastle University in England have calculated that just four liters of domestic waste water contains enough energy to illuminate a 100 Watt light bulb for five minutes. Given that the US treats up to 50 trillion liters of wastewater each year using about 1.5% of the nation's total electricity production, that's a lot of potential energy wasted. Liz Heidrich and co-workers painstakingly freeze dried water to leave behind a residue of organic volatiles account for up to 10 kilojoules per liter. This energy could be trapped by conversion to methane or hydrogen gas. Of course, finding an effective and highly energy-efficient method of tapping this resource is now needed, but at 10 kJ/l the incentive is there.
Not a waste