MN Impact: Creating New Bioenergy Products from Municipal Waste Scum

June 28, 2017

Issue

In the US, the total amount of municipal solid waste is rising each year. Millions of tons of solid waste and scum are produced annually that require safe and environmentally sound disposal. More research is needed to help turn municipal waste scum into economically feasible renewable bioenergy technologies.

What has been done

Researchers developed an economic screening method that compares the potential energy and economic value of three waste-to-energy technologies: incineration, anaerobic digestion, and biodiesel. A St. Paul, MN wastewater treatment facility producing 3175 "wet" kilograms of scum per day was used for comparison. Variables that control environmental performance were identified and evaluated including fossil fuel use, greenhouse gas emissions, eutrophication, and acidification.

Results

After applying all available subsidies, scum-to-biodiesel was shown to have the greatest economic potential, valued between $491,949 and $610,624 per year. And the incineration of scum yielded the greatest reclaimed energy potential at 29 billion kilojoules/year. The results also showed scum-to-biodiesel technology has negative impacts in all impact categories and that the benefits assigned by replacing diesel production contribute to reducing life cycle impacts significantly.