Biofuel Made from Human Excrement Has Become Easier to Produce

by Megan Geuss (Ars Technica) Wastewater treatment plants rejoice—you may have a hot commodity on your hands. -- Researchers at Pacific Northwest National Labs (PNNL) have developed a new method for treating human sewage to create a biocrude oil product that can be refined into a fuel akin to gasoline, diesel, or jet fuels.

The process is called hydrothermal liquefaction (HTL), and it has been described as a sped-up version of the way the Earth naturally creates crude oil. Researchers apply a considerable amount of heat and pressure to wastewater, breaking down its chemical components into biocrude and an aqueous liquid in minutes.

Although sewage sludge has been converted to biocrude before, previous methods were considered uneconomical because the sludge had to be dried out before conversion. HTL, on the other hand, pressurizes the sludge to 3,000 pounds per square inch and then heats it up to 660 degrees Fahrenheit (349 degrees Celsius), a process that's amenable to some liquid being present in the feedstock.

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

Using HTL, PNNL estimates that those 34 billion gallons of sewage a day could be theoretically turned into 30 million gallons of refined oil per year.

Like everything, although the method shows promise, Billings cautioned in his AMA that there are still barriers to making the process commercially viable, namely scaling up the process in a cost-effective way and proving to refiners that the biofuel is useful and marketable. READ MORE