Speaker
Douglas Call, Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, NC
Abstract
Anaerobic digestion is an established, commercial-scale technology used to treat a variety of solid wastes and high-strength wastewater while producing methane gas, which can be sold as natural gas or burned on site for energy needs. There is also growing interest in the volatile fatty acids generated by the fermentative bacteria in digesters. Volatile fatty acids (valeric acid, $6,000 / ton ) have a much larger market value than methane gas ($160 / ton). Fundamental to improving the performance of digesters or shifting product spectra is understanding and controlling the microbiology underpinning the transformation process. In this seminar, I will discuss how adding pyrogenic carbonaceous materials, including activated carbon, biochar, and graphite, influence methane production. Many prior studies hypothesized that these materials can improve electron exchange between bacteria and methanogens. Our findings suggest that other factors may play a bigger role, including the sorptive properties of these materials. To “rewire” digesters for volatile fatty acid production, I will discuss how short (minutes) exposure of digesters to elevated temperatures over time can slow or shut down methane production and increase volatile acid concentrations. Most surprising is how this approach can shift volatile fatty acid profiles toward the longer, more valuable species such as caproic acid. Collectively our results show that understanding the microbiology of digesters is essential to developing strategies that can improve or change their product spectra.
Bio
Doug Call received a BS degree in Environmental Sciences from the University of Virginia in 2003. He received a second BS degree in Civil Engineering from Virginia Tech in 2005 and then began his graduate studies in microbial electrochemical systems at Penn State University. After completing his MS and PhD in Environmental Engineering in 2008 and 2011, respectively, he joined Syracuse University as an Assistant Professor from 2012-2014. He joined NC State in 2014, where he has developed a research program focusing on biological and electrochemical approaches to recover resources from wastes.
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