Flushing a Toilet To Soon Be a Viable Alternative Energy Source

New technology turns every flush of yours into usable biocrude oil

By Rick Stella December 1, 2016

From the Toilet to the Tank – Biofuels from Sewage

In the not-so-distant future (perhaps even next year), the mere act of flushing a toilet may soon serve as an incredibly reliable source of alternative energy. A breakthrough made by the United States Department of Energy’s Pacific Northwest National Laboratory in November suggests that a new process called hydrothermal liquefaction could turn raw sewage into biocrude oil. By simply applying a bit of high pressure and temperature to a batch of sewage, an outfit such as a wastewater plant has the ability to create this bio-based fuel in roughly 45 minutes.

So how does this relate to toilets? Because a simple flush of someone’s own organic waste, if treated correctly, could help produce a few gallons of biocrude oil annually. This may not seem entirely groundbreaking but when you factor in the millions of people capable of potentially contributing to this, the number of gallons of alternative energy begin to add up extremely quickly. Furthermore, by harnessing such energy from an everyday act such as flushing a toilet, not only would it help address hygiene crises in places like India but the sheer fact someone’s toilet could serve as an energy source is revolutionary.

Sludge from Metro Vancouver’s wastewater treatment plant has been dewatered prior to conversion to biocrude oil at Pacific Northwest National Laboratory. Courtesy of WE&RF

By utilizing hydrothermal liquefaction (or HTL), the researchers that PNNL found that matter such as human waste could easily break down into “simpler chemical compounds.” To do this, the team pressurized their sample material to 3,000 pounds per square inch before inputting the sample into reactor system set to a scorching 660 degrees Fahrenheit. The exceptionally high temperature combined with the intense pressure proved to dissect the matter into separate parts, an aqueous liquid component and biofuel.

“There is plenty of carbon in municipal wastewater sludge and interestingly, there are also fats,” said Corinne Drennan, a bioenergy technologies researcher at PNNL. “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.”

A boon for the alternative energy industry, no doubt, as HTL is not only incredibly uncomplicated but wildly more efficient than using ethanol — a substance which only produces roughly the same amount of energy as it puts out. Furthermore, an independent evaluation by the Water Environment & Reuse Foundation found HTL to boast a higher “carbon conversion efficiency with nearly 60 percent of available carbon in primary sludge becoming biocrude.” It’s also worth pointing out that automobiles would have the ability to run on nothing but HTL, as opposed to ethanol which still requires being mixed with traditional gasoline.

Biocrude oil, produced from wastewater treatment plant sludge, looks and performs virtually like fossil petroleum. Courtesy of WE&RF

“The best thing about this process is how simple it is,” Drennan said. “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.”

Moving forward, the PNNL hopes to continue testing the process and developing ways in which it can help in areas ravaged by sanitation issues, along with scaling and adapting it for use on other materials.

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