Household sewage as a vast energy resource

By Michael Evans - 18 Jan 2011 14:12:2 GMT
Household sewage as a vast energy resource

There is an old North of England saying, “Where there's muck there's brass!” Roughly translated this means that money can be made from even the most unsavoury kind of rubbish.

Scientists are forever looking for new sources of energy and researchers from the UK's Newcastle University have recently been turning their attention to household sewage. Although previously not thought to be worth bothering with, the Newcastle findings have lead them to believe that household sewage has far more potential as an alternative source of energy than had previously been thought.

Their discovery indicates that the potential energy in this waste is almost 20 percent greater than had previously been thought and they consider that this is enough to spur efforts to extract methane, hydrogen and other fuels from this vast, untapped resource.

Writing in the magazine Environmental Science and Technology, Elizabeth Heidrich and her colleagues at Newcastle University took the United States as an example. In the US 12.5 trillion gallons of sewage are treated every year, but astonishingly this uses about 1.5 percent of the nation's electrical energy.

The researchers see no reason why this treatment process cannot be converted from an energy drain into an energy source. They maintain that instead of dumping all this waste, in the future there is nothing to stop the building of treatment facilities that could convert the various organic molecules into fuels.

Waste material would arrive at sewage works where it would be processed by a as a result of anaerobic digestion. This would produce biogas, which could then be used to power motor vehicles or to generate electricity. Some of the electricity could be used to power the plant, while the surplus could be sold on.

Based on new research, the scientists estimated that one gallon of waste contains enough potential energy to produce enough electricity to power a 100 watt light bulb for five minutes.

Previously there had only been one study of this potential source of energy and results had not been encouraging. Heidrich and her colleagues felt that there were far more opportunities for developing this idea than had previously been thought, so they decided to undertake a fresh study.

Heidrich considered that one of the reasons that the results of the previous study were on the low side was that some of the energy-rich compounds had been lost as a result of evaporation.

In this study the scientists collected wastewater from a sewage treatment plant in Northeast England and they first freeze-dried the sewage in order to conserve more of its energy-rich compounds.

Once this had been done they used a standard device to measure energy content and were delighted to discover that their freeze-dried waste contained 20 percent more energy that had been determined in the previous study.

Its extraction had begun to look more viable.

Funding for the new study was provided jointly by the Engineering and Physical Sciences Research Council, the School of Chemical Engineering and Advanced Materials at Newcastle University and Northumbrian Water Ltd.