Global Challenges/Chemistry Solutions

Developing new sources of energy: Producing cost-effective biodiesel from sewage sludge

August 31, 2010

Sewage sludge, shown at a wastewater treatment plant, could provide a new source of biodiesel fuel
that is cost-competitive with conventional diesel.
Credit: iStock

Summary

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 an article in ACS’ Energy & Fuels, a bi-monthly journal. Sludge is the solid
material left behind from the treatment of sewage at wastewater
treatment plants. Researchers point out in the article that demand
for biodiesel has led to the search for cost-effective biodiesel feedstocks, or raw materials. 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 seven million tons of it each year.

Who would think that that sludge flowing from sewage treatment plants could one day help power our cars and trucks? Sludge ― that’s the solid material left after treating sewage. Well, scientists have the basic technology according to a report in the American Chemical Society’s Energy & Fuels, a bi-monthly journal. Here is David Kargbo, an adjunct professor of environmental engineering at Temple University and a senior scientist with the U.S. Environmental Protection Agency in Philadelphia, author of the article…

“We have the technology today to produce biodiesel fuel from municipal sewage sludge that is within a few cents a gallon of being competitive with conventional diesel refined from petroleum. Biodiesel production from sludge could be very profitable in the long run. Right now 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. The challenge is to bring down those costs.”

The demand for biodiesel is sparking an intensive search for cost-effective biodiesel feedstocks, or raw materials. 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 seven million tons of it each year. Listen to Dr. Kargbo

“Sludge is a good source of readily available raw materials for biodiesel. To boost biodiesel production, sewage treatment plants could use microorganisms that produce higher amounts of oil. 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.”

Despite the advances in technology and the advantages of using sludge to create biodiesel fuel, researchers must solve a series of technical problems as they work to bring down the cost of this fuel.

“To make the development of biodiesel from sludge an attractive commercial venture we need to overcome some major obstacles first. These challenges include how best to collect the sludge, separate the biodiesel from other materials, maintain the quality of the biodiesel, and we have to overcome the issue of soap forming during production. Some concerns about regulating this new technology also have been raised.”

Smart Chemists/Innovative Thinking

Smart chemists. Innovative thinking. That’s the key to solving global challenges of the 21st Century. Be sure to check our previous Global Challenges podcast episodes by visiting www.acs.org/globalchallenges. Today’s podcast was written by Michael Bernstein. I’m Adam Dylewski at the American Chemical Society in Washington.

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Photo courtesy of
David M. Kargbo, Ph.D.,
Environmental Protection
Agency