Garbage Changing the Game? How Municipal Waste Is Becoming a Bioenergy Champion

by Michelle Goff (Idaho National Laboratory) As our global need for sustainable fuel grows, bioenergy is one resource that holds the key to unlocking a cleaner, more renewable energy future. Idaho National Laboratory (INL) bioenergy researcher Rebecca Brown is leading new research that supports the Department of Energy’s efforts to decontaminate municipal solid waste, specifically for use as biofuels.

“The goal of the project I’m working on is to be able to use nonrecyclable waste to create biofuels, which are any fuel sources created from biomass, or organic matter,” Brown said. “Even though not all municipal solid waste comes directly from a plant-based organism, most of the fractions we are targeting are at least indirectly derived from organic matter.”

Municipal solid waste is garbage used and thrown away in places such as homes, schools and businesses. It can include paper, plastic, food, clothing, and construction or demolition waste.

Nonrecyclable waste includes items that are either too contaminated or expensive to recycle. Some of the most common contaminants are food products, such as grease left on a pizza box, or paper products that include other materials like metal or plastic, and other waste with inorganic contaminants including dirt from yard waste. Ink and adhesives on paper are also major contamination culprits. Adhesives can cause significant problems by gumming up machinery needed to convert the paper into a form usable for biofuels.

Brown is involved in research that characterizes the municipal solid waste fractions of plastic and paper to determine what contaminants might affect biofuel conversion. They then work to decontaminate them and increase the yield for fuel and product conversion.

“As part of this project, we’ve been using high temperature conversion, or pyrolysis, to convert plastic waste to liquid oil,” Brown said. The team used two different methods to clean plastic samples – a water wash and a dimethyl ether chemical wash. With both cleaning methods, the team was able to increase the yield of liquid oil products, which was a major success for converting the plastic portions of the nonrecyclable waste.

The team did not achieve this ultimate success without some frustration. Initially, Brown tested to see if sorting plastic contaminants from the paper portion increased their yield in biochemical conversion. It didn’t. When she compared the yield from paper contaminated with ink and adhesives versus paper with different, less problematic, contaminants, she still found no difference in biochemical yield.

At long last, however, she found a solution in the form of a dilute alkaline pretreatment. Biomass researchers commonly use this solution to alter the structure of agricultural biomass and make the cellulose more accessible to enzymes. READ MORE