Peak Oil Task Force Report - City of Bloomington - State of Indiana

LONG­TERM (15­30 years)
1. Explore sludge­to­biogas energy generation
Wastewater is a rich source of organic matter, nutrients, and minerals. The products of
such wastes are potentially valuable resources, both as energy and as reusable compounds
such as phosphorus. 96 Indeed, research has demonstrated that sewage actually contains 10
times the energy needed to treat it. 97 A number of widely‐tested energy recovery
technologies have emerged to recover this energy.
Perhaps the most common way to extract energy is the sludge‐to‐biogas (methane)
process. However, such a process is reliant on anaerobic digestion. While it would likely be
very costly to transition the City’s current aerobic digestion system to an anaerobic one
capable of producing energy, the City should explore such a shift in the long term. Such
energy could be used directly for wastewater treatment, reducing the facility’s dependency
on conventional electricity. Using solids as a resource rather than a waste may help
stressed public budgets as well. Wastewater solids must be processed prior to disposal, and
solids handling accounts for as much as 30 percent of a wastewater treatment facility’s
costs. 98
Furthermore, elements like phosphorus are becoming increasingly scarce, and the recovery
and renewability of these resources is becoming economically and ecologically attractive.
Phosphorus recovery can reduce sludge volumes produced by up to 30 percent. In addition
to exploring sludge‐to‐biogas production, the City should closely examine the feasibility of
phosphorus recovery.
96 Phosphorus is a growth‐limiting nutrient that is discharged to the environment through municipal sewage. The impacts
of phosphorus discharge include severe eutrophication of fresh water bodies. The US EPA has made clear that the future
sustainable use of phosphorus must include recovery from municipal sewage and reprocessing as a fertilizer. US EPA,
Phosphorus Recovery from Sewage (2005)
http://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.abstractDetail/abstract/7345/report/F; See further,
Woods, et al, “Phosphorus Recovery Technology Modeling and Feasibility Evaluation for Municipal
Wastewater Treatment Plants,” Environmental Technology 20(7)(1999): 663‐679.
97 Global Water Research Coalition, State of the Science Report: Energy and Resource Recovery from Sludge
(2008) http://www.werf.org/AM/CustomSource/Downloads/uGetExecutiveSummary.cfm?File=ES‐
OWSO3R07.pdf&ContentFileID=6450
98 Ibid.
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