Fuel of the Future: Sewage Transformed Into Biocrude Oil

New research has presented the feasibility of turning ordinary sewage into biocrude oil. What had previously seemed like science fiction is now very possible with the discovery of the Department of Energy's Pacific Northwest National Laboratory.

Sewage has long been considered as a weak source of biofuel since it's too wet. The use of hydrothermal liquefaction, or technology that mimics the geological conditions of the Earth to create crude oil, eliminates the need for drying required in a majority of current thermal technologies. What used to take Mother Nature millions of years can now be achieved in minutes.

Organic matter such as human waste can be broken down to simpler chemical compounds. Sewage sludge is pressurized to 3,000 pounds per square inch then placed inside a reactor system that operates at about 660 degrees Fahrenheit. The heat and pressure cause the cells of the waste material to break down into different factors: biocrude and an aqueous liquid phase. This biocrude could then undergo conventional petroleum refining operations to remove small amounts of water and oxygen.

"The best thing about this process is how simple it is," said Corinne Drennan, an Energy Systems Analyst for the bioenergy technologies research at Pacific Northwest National Laboratory. "The reactor is literally a hot, pressurized tube. We've really accelerated hydrothermal conversion technology over the last six years to create a continuous, and scalable process which allows the use of wet wastes like sewage sludge."

Wastewater treatment plants across the U.S. treat approximately 34 billion gallons of sewage every day. That amount could produce the equivalent of up to approximately 30 million barrels of oil per year. Pacific Northwest National Laboratory estimates that a single person could generate two to three gallons of biocrude per year.

"There is plenty of carbon in municipal waste water sludge and interestingly, there are also fats," said Drennan. "The fats or lipids appear to facilitate the conversion of other materials in the wastewater such as toilet paper, keep the sludge moving through the reactor, and produce a very high quality biocrude that, when refined, yields fuels such as gasoline, diesel and jet fuels."

Hydrothermal liquefaction could eliminate the need for sewage residuals processing, transport and disposal, leading to significant cost savings for local governments.

.Pacific Northwest National Laboratory has licensed its hydrothermal liquefaction technology to Utah-based Genifuel Corporation, which is now working with Metro Vancouver, a partnership of local authorities in British Columbia, Canada, to build a demonstration plant.