SEES Fellows: Sustainable Nanosilicon Production through the Electrochemical Reduction of Diatoms and Integration into Wastewater Remediation and Biofuel Industries

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Project SummarySEES Fellows: Sustainable Nanosilicon Production through the Electrochemical Reductionof Diatoms and Integration into Wastewater Remediation and Biofuel IndustriesPI: Steven N. Girard, University of Wisconsin MadisonNanostructures of abundant and non-toxic silicon can serve a significant role in various renewableenergy technologies, including solar cells, Li-ion batteries, and thermoelectric materials. To realizethe potential of nanosilicon for renewable energy applications, mass quantities must be economicallyand sustainably produced. Current silicon production relies on an energy- and material- consumingcarbothermal reduction process, in which the reaction between carbon and sand (silica) at very hightemperatures yields metallurgical silicon and carbon dioxide. Metallurgical silicon is subsequentlydissolved, refined, and recrystallized in multiple energy- and material-consuming steps to generatenanosilicon for renewable energy applications. For nanosilicon to be used for renewable energy, thelarge scale production of silicon must be redesigned from a sustainability perspective. I propose todevelop an altogether new process of direct electrochemical conversion of nanosilica-to-nanosiliconthat will be energy and material efficient, and therefore inexpensive and sustainable. In collaborationwith industrial partner AlgaXperts, we will also analyze the scalability and feasibility of thisapproach through the integration into existing wastewater remediation and algae-for-biofuelindustries by essentially recycling the nanostructured diatoms (silica) from these processes.Intellectual Merit.A novel process of sustainable and direct nanosilicon production through theelectrochemical reduction of nanostructured silica frustules of diatoms will be developed. Thenaturally nanostructured silica microshells of diatoms (unicellular algae) are inexpensive and easilyobtained either from mined diatomaceous earth deposits or from diatom algal cultures. Under hostmentor Prof. Song Jin, Department of Chemistry at UW-Madison, the proposed research seeks todevelop electrochemical reduction of nanosilica within novel eutectic salt electrolytes, which willenable single-step nanosilicon production at very low temperatures, consuming considerably lessenergy. If the starting nanomorphologies can be retained following conversion to silicon, thisprocess will represent the most sustainable means of nanosilicon production to date.Broader Impact.The proposed research will be immediately useful for a variety of industrialapplications and expose the SEES fellow new chemical techniques. We further propose harvestingspecific diatom genera from industrial-scale algal cultures used for the bioremediation of wastewatereffluent and production of lipids for biofuels. Obtaining specific diatom genera allow control overthe types of nanostructures obtained. In collaboration with partner mentor Jun Yoshitani, Presidentof AlgaXperts LLC, we will analyze the feasibility of the integration of these approaches at aMidwestern water treatment facility. Furthermore, this collaborative research will involve chemicalanalysis of the wastewater effluent nutrients, selectivity of specific genera in industrial-scale cultures,and analysis of the associated costs. The SEES fellow will gain a better understanding of theindustrial considerations connected to implementing large-scale sustainability technologies.Educational Outreach.In collaboration with Prof. Greg Nemet, Nelson Institute of EnvironmentalStudies at UW-Madison, and Dr. Andrew Greenberg, Director of REU programs at UW-Madison, ahighly interdisciplinary summer practicum focusing on public policy and sustainability science willbe designed and implemented. Lessons learned in the primary research will be integrated into theREU summer practicum. In collaboration with Dr. Greenberg, underrepresented minorityundergraduate researchers will be mentored by the SEES fellow in summer research projects relatedto the proposed research. The SEES fellow will gain experience in sustainability policy, teaching,course design, integration of teaching and research, and undergraduate mentoring.