Sediment microbial fuel cells (SMFCs) are expected to be used as a renewable power source for remote environmental monitoring; therefore, evaluation of their long-term power performance is critical for their usability. In' this paper, we present novel data needed to understand the long-term performance of SMFCs. We used 3-D Microemulsion (3DMe)(TM) doped anodes, which slowly release lactate and its fermented products. During our tests, anode-limited SMFCs with and without 3DMe-doped anodes were operated for more than 18 months with a load simulating a sensor operation. We found that dclping an anode with an electron donor reduced startup time and increased maximum power (55 +/- 2 mu W compared to 46 +/- 2 mu W) in the control systems. We found that the long-term steady power performance is approximately 33% of the maximum power (similar to 18 LW). Finally, our small-sized SMFCs generated higher power densities than those in the literature (28 mW/m(2) versus 4 mW/m2). Using electron donor doped anodes can be practical when a short startup time and initial high power are needed. However, if long-term power is critical, the addition of an electron donor does not provide a practical advantage. In addition, in long-term operation enrichment of the anode surface with electrochemically active bacteria does not provide any advantage. (C) 2016 Elsevier Ltd. All rights reserved.