Sewage Sludge May Soon Fuel Airplanes

New technology may make it possible for sewage sludge to fuel airplanes, a development that’s part of a growing fleet of innovations impacting where waste plant managers send the sludge that is a byproduct of their daily operations.

The latest innovation comes out of the Pacific Northwest National Laboratory (PNNL), a U.S. Energy Department government research lab based Richland, WA.

Here’s what’s new about PNNL’s breakthrough, per the lab: “Sewage, or more specifically sewage sludge, has long been viewed as a poor ingredient for producing biofuel because it's too wet. The approach being studied by PNNL eliminates the need for drying required in a majority of current thermal technologies which historically has made wastewater to fuel conversion too energy intensive and expensive.”

The technology will come into use in the near future, and it has the potential to create fuel for cars, trucks, and planes, just to name a few applications. “Genifuel Corporation, a Utah-based company that makes renewable fuel equipment, has licensed the technology and is currently working with Metro Vancouver to build a demo plant,” The New York Post reported.

“They hope the approximately $9 million plant could start construction as early as 2018. If the demo is successful, the technology has the potential to pump out 30 million barrels of oil a year,” the report said.

The backdrop is that PNNL researchers “have figured out how to transform sewage sludge into a biocrude that can be processed at conventional petroleum refining plants and turned into gasoline, diesel or jet fuel,” Crosscut reported.

“Burning this fuel still produces greenhouse gases, but transforming our waste back into energy results in lower net carbon emissions than using fossil fuels pumped or mined from the earth. And sewage fuel is most promising as a replacement for things like jets, which can’t run on electricity or batteries,” the report continued.

The big picture is this, according to PNNL: The 34 billion gallons of sewage the U.S. treats on a daily basis could produce 30 million barrels of oil per years. The sewage produced by each U.S. resident can create two to three gallons or biocrude per year, the report said.

The process of hydrothermal liquefaction is similar to, but quicker than, natural processes that turn plant material to oil, according to the Crosscut report. The sewage is placed in a pressurized, heated tube, which breaks down carbon and creates a product similar to petroleum. The process was originally created with the idea of using algae, but sewage may be cheaper and more widely available.

Justin Billing, a chemical and biological process development engineer with PNNL, said experiments with sewage sludge began last year and have been showing success. He explained the evolution from using algae to using sewage sludge. “We had this idea because [sewage sludge] has the same biochemical profile as algae, the same ratio of lipids, carbohydrates and proteins,” he said, per the report.

The practice may be more sustainable than the use of conventional fossil fuels.

“Over the whole life cycle, wastewater biofuel results in 55 to 70 percent less greenhouse gas emissions compared to petroleum. In part, that’s because the way it stands, a lot of our sewage solids eventually end up being transported from wastewater treatment plants to landfills, where its decomposition produces carbon dioxide and methane,” the report said.

For similar stories visit Water Online’s Sludge And Biosolids Processing Solutions Center.