A team of Washington State University researchers, including some based at the WSU Tri-Cities campus, have found a new method to treat sewage that reduces the costs of wastewater treatment while also creating renewable natural gas. 

The researchers’ study, recently published in the Chemical Engineering Journal, showed that pretreating sewage sludge with high temperatures and pressure and oxygen before undergoing typical wastewater treatment steps cut final disposal costs in half while producing 200% more renewable natural gas. 

“This technology basically converts up to 80% of the sewage sludge into something valuable,” said Birgitte Ahring, corresponding author on the paper and a professor in WSU’s Bioproducts, Sciences, and Engineering Laboratory at WSU Tri-Cities and the Gene and Linda Voiland School of Chemical Engineering and Bioengineering, in a statement. “If we can replicate this work on other organic materials, we’ll have a waste treatment technology that is world-class when it comes to efficiency.” 

About half of the country’s 15,000 wastewater treatment plants use anaerobic digestion to reduce sewage waste and make biogas. However, that process is inefficient, produces biogas of limited use and still leads to many of the resulting solids ending up in landfills. Wastewater treatment processes also require significant electricity. 

Ahring and her colleagues found that heating up and adding pressure and oxygen to sewage before treatment makes anaerobic digestion more efficient. The team then used a novel bacterial strain that they discovered and isolated to upgrade the biogas which comes out as nearly pure methane.  

The researchers are working with WSU’s Office of Innovation and Entrepreneurship and have patented the bacterial strain. They are now working with an industrial partner to develop a larger scale project.