Education

Research Description

Dr. Call's research focuses on technologies at the interface of the water-energy nexus. In particular, he is interested in recovering resources, such as energy and nutrients, from wastewater. He combines his multidisciplinary background in microbiology, molecular biology, and electrochemistry to research hybrid bioelectrochemical technologies, such as microbial fuel cells, that convert liquid and gaseous wastes into energy and high-value products. Other research topics Dr. Call is working on include biological-based methane mitigation from engineered environments, methane generation in anaerobic systems, and salinity-gradient energy recovery.

Publications

Junction potentials bias measurements of ion exchange membrane permselectivity

Kingsbury, R. S., Flotron, S., Zhu, S., Call, D. F., & Coronell, O. (2018), Environmental Science & Technology, 52(8), 4929-4936.

Impact of solution composition on the resistance of ion exchange membranes

Zhu, S., Kingsbury, R. S., Call, D. F., & Coronell, O. (2018), Journal of Membrane Science, 554, 39-47.

Impact of solution composition on the resistance of ion exchange membranes

Zhu, S., Kingsbury, R. S., Call, D. F., Coronell, O. (2018), Journal of Membrane Science, 554, 39-47.

Impact of natural organic matter and inorganic solutes on energy recovery from five real salinity gradients using reverse electrodialysis

Kingsbury, R. S., Liu, F., Zhu, S., Boggs, C., Armstrong, M. D., Call, D. F., & Coronell, O. (2017), Journal of Membrane Science, 541, 621-632.

Hardwiring microbes via direct interspecies electron transfer: Mechanisms and applications

Cheng, Q. W., & Call, D. F. (2016), Environmental Science-Processes & Impacts, 18(8), 968-980.

Substrate and electrode potential affect electrotrophic activity of inverted bioanodes

Hartline, R. M., & Call, D. F. (2016), Bioelectrochemistry, 110, 13-18.

Microbial power-generating capabilities on micro-/nano-structured anodes in micro-sizedmicrobial fuel cells

Fraiwan, A., Adusumilli, S. P., Han, D., Steckl, A. J., Call, D. F., Westgate, C. R., & Choi, S. (2014), Fuel Cells, 14(6), 801-809.

Geobacter sp SD-1 with enhanced electrochemical activity in high-salt concentration solutions

Sun, D., Call, D., Wang, A. J., Cheng, S. A., & Logan, B. E. (2014), Environmental Microbiology Reports, 6(6), 723-729.

View all publications via NC State Libraries

Grants

EAGER Electrically Driving the Microbial Conversion of Nitrogen Gas into Ammonia

National Science Foundation (NSF)(8/15/18 - 7/31/19)

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EAGER Electrically Driving the Microbial Conversion of Nitrogen Gas into Ammonia

Sponsor: National Science Foundation (NSF)

Start Date: 8/15/18

End Date: 7/31/19

Abstract

Nitrogenous fertilizers are critical for sustaining small to large farms in the US. The Haber-Bosch process generates the majority of fixed nitrogen, but it comes at a high cost, both in terms of dollars and environmental impact. Requiring temperatures between 400-500oC and pressures of 150-250 bar, this process consumes 1-2% of global energy. Reliance on fossil fuels to power this process translates into unstable fertilizer prices and a significant release of greenhouse gases. Low-cost and carbon-neutral ammonia fertilizer production is therefore needed to improve the sustainability of our food production systems. Biological nitrogen (N2) fixation, as practiced in the farming of legumes, is attractive because of its low-energy demand, operation under ambient conditions, and point-of-use production; however, slow fixation rates and, in the case of non-legume crops, a lack of abundant N2 fixing symbiotic diazotrophs in the soil, limit the large-scale feasibility of this approach. Moreover, options to accelerate symbiotic N2 fixation rates to the industrial levels needed to compete with the Haber-Bosch process are lacking. As an alternative, we propose investigating a hybrid microbial electrochemical system to electrically enhance microbial N2 fixation rates. Bacteria in these systems consume organic matter (such as waste biomass) and generate electrical current when they respire (breathe) on anode electrodes. By exploiting their physiology, we hypothesize that we can electrically “boost” N2 fixation rates in these organisms. The overall objective of this proposal is to determine the influence of the electrical driving force on the rates, mechanisms, and pathways of microbial N2 fixation. The rationale is that with this knowledge, we can improve N2 fixation rates in these communities and optimize a scalable technological platform to produce fixed nitrogen from small-scale farms to industrial-scale applications.

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Electrically Assisted Sorption and Desorption of Per- and Polyfluoroalkyl Substances

Strategic Environmental Research and Development Program (SERDP)(5/16/18 - 5/16/19)

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Electrically Assisted Sorption and Desorption of Per- and Polyfluoroalkyl Substances

Sponsor: Strategic Environmental Research and Development Program (SERDP)

Start Date: 5/16/18

End Date: 5/16/19

Abstract

The removal of per- and polyfluoroalkly substances (PFASs) from contaminated groundwater is required to minimize human exposure to these compounds. Activated carbon is a widely used sorbent to remove PFASs, but it suffers from two limitations: 1) the inability to remove short-chain PFASs, and 2) the lack of cost-effective regeneration methods. The overall objective of this proposal is to electrically enhance adsorption of high priority PFASs onto activated carbon and electrically discharge them as an innovative, chemical-free regeneration technique.

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Methane Conversion to Electrical Current using Microbial Electrochemical Technologies

NCSU Research and Innovation Seed Funding Program(1/01/15 - 12/31/15)

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Methane Conversion to Electrical Current using Microbial Electrochemical Technologies

Sponsor: NCSU Research and Innovation Seed Funding Program

Start Date: 1/01/15

End Date: 12/31/15

Abstract

The unprecedented supplies of natural gas in the US could have a significant impact on our growing demand for transportation fuels. The lack of an appropriate natural gas distribution infrastructure coupled with complex and costly conventional methods to generate drop-in fuels from natural gas are major barriers to realizing this impact. In this collaborative proposal between CoE and CALS, we will investigate the ability of naturally occurring microorganisms to convert methane gas (the major component of natural gas) into electrical current using a cutting-edge, recently commercialized microbial electrochemical technology. This electrical current can subsequently be used to generate liquid fuels or their precursors in these devices. This approach is potentially transformative because it circumvents the complexity associated with recent efforts to accumulate and extract fuel precursors from within methane-oxidizing microorganisms. Seed funding from RISF will allow us to obtain essential preliminary data to secure multi-year external funding from sources with interests in Energy and the Environment, such as the DOE and NSF.

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Improving the Anaerobic Treatment of Biosolids and High-Strength Waste Streams through Addition of Electrically-Conductive Particles

NCSU Water Resources Research Institute(3/01/15 - 12/31/16)

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Improving the Anaerobic Treatment of Biosolids and High-Strength Waste Streams through Addition of Electrically-Conductive Particles

Sponsor: NCSU Water Resources Research Institute

Start Date: 3/01/15

End Date: 12/31/16

Abstract

North Carolina has a tremendous need for efficiently treating high-strength waste streams. These include agricultural residuals, food wastes, and wastewater-derived biosolids. Anaerobic digestion is one promising treatment and energy recovery method, but several limitations prevent widespread adoption. One of which is the instability that can arise from disruptions between key groups of microorganisms and another is the incomplete conversion of organics to methane gas (CH4). To overcome these limitations, we propose augmenting anaerobic digesters with electrically conductive micro-scale particles. These particles have proven effective as conduits for microbe-to-microbe direct electron transfer, resulting in improved rates of CH4 generation using pure strains in the lab. We hypothesize that supplementing anaerobic digesters with these particles will improve stability and CH4 recovery by strengthening interspecies electron transfer between the two central microbial communities: syntrophic bacteria and the methane-generating methanogens. Our objectives are to (1) determine the impact of various particle properties (type, conductivity, size) on organics removal and CH4 generation, (2) determine optimal particle loading densities for two distinct waste streams, and (3) assess the settleability of particle-augmented waste. To do this, we will operate lab-scale anaerobic digesters with and without conductive particles (activated carbon, magnetite, biochar). These findings will be especially beneficial for wastewater treatment facilities and farmers around the state looking for strategies to tip the economics in favor of anaerobic digestion technology while ensuring the health of our water resources.

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