Microbial battery for efficient energy recovery

Departments of ^aCivil and Environmental Engineering,
^bMaterials Science and Engineering, and
^cChemistry, Stanford University, Stanford, CA 94305; and
^dStanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025

Edited by Harry B. Gray, California Institute of Technology, Pasadena, CA, and approved August 9, 2013 (received for review April 18, 2013)

Significance

This work introduces a microbial battery for recovery of energy from reservoirs of organic matter, such as wastewater. Microorganisms at an anode oxidize dissolved organic substances, releasing electrons to an external circuit, where power can be extracted. The electrons then enter a solid-state electrode that remains solid as electrons accumulate within it. The solid-state electrode is periodically removed from the battery, oxidized, and reinstalled for sustained power production. Molecular oxygen is not introduced into the battery, and ion-exchange membranes are avoided, enabling high efficiencies of energy recovery.

Abstract

By harnessing the oxidative power of microorganisms, energy can be recovered from reservoirs of less-concentrated organic matter, such as marine sediment, wastewater, and waste biomass. Left unmanaged, these reservoirs can become eutrophic dead zones and sites of greenhouse gas generation. Here, we introduce a unique means of energy recovery from these reservoirs—a microbial battery (MB) consisting of an anode colonized by microorganisms and a reoxidizable solid-state cathode. The MB has a single-chamber configuration and does not contain ion-exchange membranes. Bench-scale MB prototypes were constructed from commercially available materials using glucose or domestic wastewater as electron donor and silver oxide as a coupled solid-state oxidant electrode. The MB achieved an efficiency of electrical energy conversion of 49% based on the combustion enthalpy of the organic matter consumed or 44% based on the organic matter added. Electrochemical reoxidation of the solid-state electrode decreased net efficiency to about 30%. This net efficiency of energy recovery (unoptimized) is comparable to methane fermentation with combined heat and power.

Footnotes

¹To whom correspondence may be addressed. E-mail: yicui@stanford.edu or ccriddle@stanford.edu.

Author contributions: X.X., C.S.C., and Y.C. designed research; X.X., M.Y., P.-C.H., and N.L. performed research; X.X., M.Y., C.S.C., and Y.C. analyzed data; and X.X., M.Y., P.-C.H., N.L., C.S.C., and Y.C. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1307327110/-/DCSupplemental.