WSU pilot turns sewage sludge into renewable gas, cuts treatment costs by half

Pullman, WA: A new method for treating sewage sludge not only produced 200% more renewable natural gas than current practices but also slashed disposal costs nearly in half, according to a pilot study from Washington State University.

The process, described this week in the Chemical Engineering Journal, offers communities a way to clean up waste while generating energy without the heavy climate impact of fossil fuels.

Researchers pretreated sludge collected from a nearby wastewater facility before processing it. The result: the system converted up to 80% of the sewage sludge into valuable renewable natural gas. “This technology basically converts up to 80% of the sewage sludge into something valuable,” said Professor Birgitte Ahring of WSU’s School of Chemical Engineering and Bioengineering, one of the paper’s authors.

The renewable gas can be used like conventional natural gas — for electricity generation, home heating, or transportation — but with a much smaller carbon footprint. Beyond energy, the method cuts the cost of sludge disposal by nearly 50%, a major expense for wastewater plants.