Turning Wastewater Scum Into a Profitable Resource

Researchers at the University of Minnesota are developing a new process which converts wastewater scum, a treatment byproduct, into biodiesel. This promising new research could provide the wastewater industry with another valuable outlet for protecting the environment and helping to reduce overall costs. Preliminary research provides convincing evidence that there is enough energy-dense waste oil contained within wastewater scum to make it a viable and profitable avenue for conversion to vehicle fuel.

Traditionally 70 – 80% of the cost of creating biodiesel is realized from the price of purchasing the initial oil. This new process will utilize a waste material that currently has no commercial value and which represents a hard cost to taxpayers to landfill. The process would take place in three important stages.

  1. Usable oil is separated from non-oil organics, metals and water through physical and chemical extraction.
  2. The scum is then converted to biodiesel in a one-step process.
  3. A post-conversion distillation occurs.

The result is a transparent product that meets ASTM International guidelines for commercial use biodiesel.

Initial testing and development took place at a research pilot processing facility at the University of Minnesota. The St. Paul wastewater treatment facility provided the necessary wastewater scum to run the project and they are prepared to install the process at their facility once pilot-scale testing is completed.

The benefits to the utility are expected to be immediate, as they are predicted to realize savings from reducing the amount of wastewater scum they currently landfill by over 85%. Additional benefits, beyond more efficient disposal of organic wastes, will come from producing enough renewable fuel onsite that the utility will be able to power nearly 20% of their petroleum diesel vehicle fleet. Researchers estimate that once the installation occurs, the fuel produced could have an innate value of nearly $400,000, which could reach over $600,000 when they account for federal tax incentives and renewable credit programs.

The research team at the University of Minnesota feels confident that their process, once the pilot phase reaches completion, will be able to benefit wastewater treatment operations on a global scale. The research team balance believes that their technology will work at any scale and the completion of a full-scale, scum-to-biodiesel process would the first major step towards commercial application.

This new research promises to add another avenue for the wastewater industry to extract valuable material from influent and to reduce their bottom line while benefiting the environment. Much like using biogas produced from anaerobic biomass digestion, or thermally conditioned sewage sludge that wastewater outlets offer to farmers as fertilizer, the conversion of wastewater scum into biodiesel could prove to be another serious opportunity to keep the industry sustainable and more profitable for years to come.