Environmental Protection

Sewage Sludge Could be a Competitive Feedstock for Biodiesel

Existing technology can produce biodiesel fuel from municipal sewage sludge that is within a few cents a gallon of being competitive with conventional diesel refined from petroleum, according to the article, “Biodiesel Production from Municipal Sewage Sludges,” which was published in Energy & Fuels, a bimonthly journal.

Author David M. Kargbo, Ph.D., with U.S. Environmental Protection Agency Region 3's Office of Innovation, Environmental Assessment & Innovation Division, points out that demand for biodiesel has led to the search for cost-effective biodiesel feedstocks. Soybeans, sunflower seeds and other food crops have been used as raw materials but are expensive. Sewage sludge is an attractive alternative feedstock — the United States alone produces about 7 million tons of it each year. To boost biodiesel production, sewage treatment plants could use microorganisms that produce higher amounts of oil, Kargbo said. That step alone could increase biodiesel production to the 10-billion-gallon mark, which is more than triple the nation’s current biodiesel production capacity, the report indicated.

To realize such commercial opportunities, however, stakeholders must overcome the challenges of collecting the sludge, separating biodiesel from other materials, maintaining biodiesel quality, addressing soap formation during production, and meeting regulatory concerns.

When those challenges are addressed, “Biodiesel production from sludge could be very profitable in the long run,” the report stated. “Currently the estimated cost of production is $3.11 per gallon of biodiesel. To be competitive, this cost should be reduced to levels that are at or below [recent] petro diesel costs of $3.00 per gallon.”

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