Animal manures, wastewater, and food waste might seem out of sight, out of mind. But when processed using waste-to-energy technology, they one day will be at the forefront of awareness—taking up residence in products like plastics as well as serving as fuels for cars and airplanes.

PNNL researchers are providing thought leadership around waste-to-energy efforts for the U.S. Department of Energy’s Bioenergy Technologies Office (BETO). These efforts build on PNNL’s groundbreaking research to turn wastewater sludges into biocrude oils—oils that can be converted to transportation fuels using conventional methods.

To HTL and beyond

Hydrothermal liquefaction, or HTL, uses high pressure and temperature to convert wet waste into crude oil, but the process only takes minutes—not millions of years. The PNNL-developed technology has shown that biocrudes from wastewater sludge and a few other wet wastes can be refined using conventional petroleum refining operations.

HTL offers several advantages over other thermochemical conversion methods. It works best with wet biomass, not requiring expensive and lengthy processes to dry the material. It can transform almost all the biomass into biocrude oil, leaving less waste destined for the landfill. It also offers opportunities to recover valuable nutrients, such as phosphorous, for applications such as fertilizer.

Expanding on the HTL technology, PNNL is now performing cost-benefit analyses of energy production and resource recovery at wastewater treatment plants, including more than 15,000 publicly owned treatment facilities. These analyses will inform strategies to recover 170 trillion BTU/year of energy contained in wastewater. 

We’re also working on feasibility assessments for using HTL technology to transform underused wet wastes, such as manures at more than 32,000 confined animal operations across the United States.

Waste-to-energy for biofuels

Our researchers are also supporting BETO’s overarching goal to develop viable bioenergy technologies for advanced biofuels that meet DOE’s cost target. To this end, PNNL is performing lifecycle impact and techno-economic analyses for processing wet wastes via HTL.

Someday soon, those odious animal manures or wastewater sludges could be just the material that powers your next family car trip.