In the international effort to cut greenhouse gas emissions, the production of biofuels as a replacement for petroleum-based transportation fuels takes center stage. In the College of Engineering, the Environmental Microbiology and Biotechnology (EMB) Group is investigating a novel high-temperature approach to producing renewable energy from biosolids, animal manure, and cellulosic biomass with a one-year, $57,000 grant from American Refining and Biochemical Company.
“The combustion of fossil fuels accounts for 73 percent of carbon dioxide, the most important greenhouse gas in the atmosphere,” says Yasemin Dilsad Yilmazel, a Ph.D. candidate who is conducting this research project. “The goal of this research is to produce alternative biofuels such as ethanol and hydrogen from landfilled materials like wastewater biosolids and farm waste such as animal manure.”
When left to decompose in a landfill, biosolids produce significant quantities of “landfill gas,” comprised mostly of methane, which is 23 times more potent than carbon dioxide and a significant source of global warming potential. Public utilities pay up to $120 per ton to transport biosolids to a landfill. Similarly, animal manure emits methane and carbon dioxide when left to waste or when used as agricultural fertilizer. When not managed effectively, animal manure poses an environmental and public health risk.
For this research, biosolids, animal manure, and cellulosic biomass materials will be used as feedstock to produce ethanol (which improves combustion efficiency) and hydrogen (which is considered a clean fuel that emits no carbon dioxide) through the process of high-temperature microbial fermentation.
High temperatures accelerate enzymatic catalysis rates, which enhance the break-down of cellulosic materials. They also improve fermentation stability because few contaminating organisms will survive the high temperatures. High temperature conversions also eliminate the need for materials pretreatment, which reduces production costs.
First, Yilmazel will develop cultures of A. thermophilum, a bacterial strain that grows optimally at temperatures between 172 and 176 degrees Fahrenheit. Then, she will combine the bacteria with the feedstock in a bench-scale hyperthermophilic anaerobic digester. As the bacteria break down the feedstock, the result is ethanol and hydrogen. Several bench-scale digesters will be developed to optimize process and operating parameters (feed stock characteristics, loading rate, mixing intensity) for maximum yield.
If successful, this research could be replicated for production of ethanol and hydrogen on a commercial scale. In the process, it represents the diversion of an otherwise waste material into a beneficial use, while reducing waste management costs for public utilities and farm operations.