PFI-RP: Conversion of Organic Wastes Streams by Torrefaction for Bio-Power Application

The broader impact/commercial potential of this PFI project is the production of clean, renewable, and affordable solid fuel pellets produced from torrefied waste-plastic blend as a drop-in fuel for use in coal power plants. The use of waste as a feedstock for a clean fuel (void of chlorine, sulfur, and nitrogen) will prevent ecological damage, due to landfilling, and will advance the health and welfare of the American public by reduced air emissions. The pellets are of high calorific value and at low cost that will compete with fossil coal, increasing the economic competitiveness of the U.S. This effort is enhancing partnerships between academia and industry (two partners from the academia and one from the industry) in the U.S. The program has significant educational contributions, both at Michigan Technological University and the University of Idaho, and will prepare Ph.D. students for this emerging field in the workplace. Finally, this work will improve public scientific literacy and engagement with science and technology in the U.S., by advancing this area.

The proposed project deals with torrefaction of solid waste that comprises mostly fiber and plastic to convert them into clean, high-calorific-value solid fuels. The main challenges in using solid wastes for energy applications are: (1) inhomogeneity within the waste streams; (2) materials in the waste that are hazardous to the environment and equipment, such as chlorine and potassium; and (3) the converted fuel should be grindable to enable its applications in coal-fired boilers. The team, comprising two academic institutions and a commercial entity, is developing new approaches to solve these hurdles. Inhomogeneity is being resolved by sorting metals and glass and blending the sorted waste with fiber or plastic waste to obtain a consistent blend. Torrefaction is helping to solve the two latter hurdles. During torrefaction, the material becomes brittle and hence can be pulverized to the required size. The hazardous materials are removed after torrefaction, by dissolving the brittle material in aqueous solution that dissolved the hazardous material, specifically chlorine and potassium. Plastic has been found to play a major role in the quality of final pellets, as it increases the calorific value and enables producing high density pellets that are safe, durable, and water resistant.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.