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The high internal resistance (Rint) that develops across the sediment microbial fuel cells (SMFC) limits their power production (~4/10 mW m−2) that can be recovered from an initial oil-contaminated sediment (OCS). In the anolyte, Rint is related to poor biodegradation activity, quality and quantity of contaminant content in the sediment and anode material. While on the catholyte, Rint depends on the properties of the catholyte, the oxygen reduction reaction (ORR), and the cathode material. In this work, the main factors limiting the power output of the SMFC have been minimized. The power output of the SMFC was increased (47 times from its initial value, ~4 mW m−2) minimizing the SMFC Rint (28 times from its initial value, 5000 ohms), following the main modifications. Anolyte: the initial OCS was amended with several amounts of gasoline and kerosene. The best anaerobic microbial activity of indigenous populations was better adapted (without more culture media) to 3 g of kerosene. Catholyte: ORR was catalyzed in birnessite/carbon fabric (CF)-cathode at pH 2, 0.8M Na2SO4. At the class level, the main microbial groups (Gammaproteobacteria, Coriobacteriia, Actinobacteria, Alphaproteobacteria) with electroactive members were found at C-anode and were associated with the high-power densities obtained. Gasoline is more difficult to biodegrade than kerosene. However, in both cases, SMFC biodegradation activity and power output are increased when ORR is performed on birnessite/CF in 0.8 M Na2SO4 at pH 2. The work discussed here can focus on bioremediation (in heavy OCS) or energy production in future work.

Biodegradation of oil-contaminated sediments (OCS) in sediment microbial fuel cells (SMFC) is limited by several factors such as adapted microorganisms to degrade OCS, low conductivity and organic matter content, sluggish cathodic O2 reduction reaction (ORR), among others. The use of a birnessite/Carbon Fabric (CF) cathode improves the O2 reduction in SMFC. Oil-contaminated sediments amended with chitin (commercial analytical grade (CC) and dried natural shrimp shells (NC)) allows faster anaerobic biodegradation in the anolyte by the indigenous bacteria coming in the initial OCS, without further growth media. The SMFC containing the unmodified OCS produces a maximum power output of 5 mW m−2 in contrast to 62 mW m−2 and 178 mW m−2 of that SMFC containing CC and NC, respectively. High-power output of SMFC is the result of minimizing internal resistance by combining the following key factors: a) saturated air 0.8 M Na2SO4 catholyte at pH 2, b) the use of a birnessite/CF-cathode, and c) the presence of bacterial groups enriched on the anode biofilm as Deltaproteobacteria and Bacteroidetes, additional to other groups such as Aminocenantia depending on the source of chitin. The pH of the catholyte strongly modifies the power production of SMFC; a detailed discussion is included in this paper.