Game-changing garbage? How municipal waste becomes bioenergy champions | Local

Michelle Goff National Laboratory of Idaho

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

“The goal of the project I’m working on is to be able to use non-recyclable waste to create biofuels, which are all 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 target are at least indirectly derived from organic matter.”

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

Non-recyclable waste includes items that are 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 containing other materials such as metal or plastic, and other waste containing inorganic contaminants, including garden waste dirt. Ink and adhesives on paper are also the main contributors to contamination. Adhesives can cause significant problems by gumming up the machinery needed to turn paper into a usable form for biofuels.

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

“In this project, we used high-temperature conversion, or pyrolysis, to convert waste plastics into liquid oil,” Brown said. The team used two different methods to clean the plastic samples: a water wash and a chemical wash with dimethyl ether. With both cleaning methods, the team was able to increase the yield of liquid petroleum products, which has been a major success for the conversion of plastic parts from non-recyclable 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. This was not the case. When she compared the performance of paper contaminated with ink and adhesives to that of paper containing different, less problematic contaminants, she still found no difference in biochemical performance.

However, she finally found a solution in the form of a dilute alkaline pre-treatment. Biomass researchers commonly use this solution to modify the structure of agricultural biomass and make cellulose more accessible to enzymes.

For Brown, this pre-treatment method helped decontaminate some of the mixed paper products that passed through the system.

Their success to date will provide full support to biorefineries striving to better decontaminate the paper product samples they receive.

The success of the project has earned additional funding from the Department of Energy’s Office of Bioenergy Technologies. The primary goal of this ongoing research is to find low-cost decontamination strategies, so the team can make municipal solid waste a more economically feasible feedstock for biofuel conversion.

“Right now, contaminated municipal waste has a bit of a negative value,” Brown said. “There’s not much we can do with it when it’s landfilled. The average rate of contamination of recyclable materials is 17%. If we succeed in decontaminating this waste and using it as fuel, its efficiency explodes beyond that of standard recyclable waste. Beyond that, if we can implement these strategies in biorefineries, our decontamination opportunities could become available nationally and even globally.

Battelle Energy Alliance manages INL for the US Department of Energy’s Office of Nuclear Energy. INL is the national center for nuclear energy research and development and also conducts research in each of the DOE’s strategic areas: energy, national security, science, and the environment. For more information, visit Follow us on social networks: Twitter, Facebook, Instagram and LinkedIn.

Melissa C. Keyes