Turning Sewage Sludge into Biocrude

Researchers at the U.S. Department of Energy’s Pacific Northwest National Laboratory (PNNL) have produced a “biocrude” oil that can be further refined into liquid fuels similar to petroleum products. Hydrothermal processing (HTP) uses similar conditions used by nature to create crude oil underground. HTP pressurizes the sludge to about 3,000 pounds per square inch, and then feeds it into a reactor that operates at about 660 degrees Fahrenheit. The heat and pressure breaks down the cells of the feedstock into the biocrude oil and “an aqueous liquid phase,” which can then be treated and used to create other fuels and chemical products. HTP is able to turn 60 percent of the available carbon in the sewage sludge into biocrude, with the other byproducts being a methane-rich gas (also a fuel) and water.

This technology, when scaled up, has the potential to turn municipal wastewater treatment plants into renewable energy producers, while “virtually eliminating” the need for the processing, transport and disposal of residuals from sewage treatment. Each year, the U.S. produces 34 billion tons of sewage and if all wastewater treatment plants used HTP, it could produce the equivalent of up to 30 million barrels of oil from that sewage waste.

By enabling the use of a wet feedstock, this HTP process could open a lot of new doors for cleaner liquid fuels from organic materials, including agricultural waste, that has previously been dismissed as being inappropriate for biofuel production due to the need to dry them before using, which rendered them both expensive and energy-intensive to convert into fuels. PNNL has licensed the new technology to Genifuel Corporation, based in Utah, which is working toward the creation of a demonstration plant with Metro Vancouver that could be operating as soon as 2018. And for those interested in a lifecycle analysis of the HTP process, PNNL has you covered right here.

By Efrain Esparza, ESG Writer

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