According to the Water Environment Research Foundation wastewater sludge could be a new resource for alternative energy.In a press release issued Friday, the group says researchers are exploring sustainable wastewater treatment with a reduced carbon footprint. “The view of municipal sewage has shifted, from a waste to be treated and disposed of, to a resource that can be processed for recovery of energy, nutrients, and other constituents,” it says.

The group notes that, “research has demonstrated that sewage actually contains 10 times the energy needed to treat it, and it is technically feasible to recover energy from sludge. As renewable energy, it can be directly used for wastewater treatment, reducing the facility’s dependency on conventional electricity.”

The release notes there are about 2,000 central sludge processing facilities in the U.S. As of 2004, 650 of those facilities used anaerobic digesters to process its sludge. When sludge is digested, it produces methane gas. According to the release, the Water Environment Research Foundation developed the Life Cycle Assessment Manager for Energy Recovery (LCAMER) model to help wastewater agencies determine the feasibility of recovering energy from anaerobic digestion of wastewater solids.

The foundation also notes these examples of energy conversion:

  • The city of Watsonville, California uses restaurant grease to increase sewage sludge digester gas production by over 50 per cent.
  • The use of methane as a source of hydrogen has been demonstrated at King County (WA) South Treatment Plant.
  • In 2005 in the U.K., waste (including sewer sludge) combustion and biogas production accounted for 10.8 percent and 4.2 percent respectively of all UK renewable energy.
  • A German plant produces excess energy. In 2005, an average of 113 per cent of the electricity consumed in the operation of the plant was generated onsite by gas engines.
  • A Swedish treatment plant produces and sells biogas to Stockholm’s bus company, which uses it to run at least 30 buses.
  • Stockholm’s energy company uses heat recovery pumps to extract heat from treated sewage to provide hot water and heating to 80,000 apartments.
  • The Sewerage Bureau of Tokyo Metropolitan Government turns dewatered sewage sludge into fuel charcoal for thermal power generation.
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