Microbial fuel cells (MFCs) are bio-electrochemical devices that use microbial metabolic processes to convert organic substances into electricity with high efficiency. In this study, the performance of a soil-based MFC using urine as a substrate was assessed using polarization and power density curves. A single-chamber, membrane-less MFC with a carbon-felt air cathode and a carbon-felt anode fully buried in biologically active soil was constructed to examine the impact of urine treatment on the performance of the MFC. The peak power of the urine-treated MFC was 124.16 mW/m(2) and was obtained 24 hours after the first urine addition; a control MFC showed a value of 65.40 mW/m(2) in the same period. The treated MFC produced an average power of 70.75 mW/m(2) up to 21 days after the initial urine addition; the control MFC gave an average value of 4.508 mW/m(2) over the same period. The average internal resistances of the treated MFC and the control MFC obtained after the initial treatment were 269.94 and 1627.89 Omega, respectively. This study demonstrates the potential of human urine to reduce internal losses in soil MFCs and to provide stable power densities across various external resistors. These results are propitious for future advancements in soil MFCs for power generation utilizing human urine (a readily available source of nutrients) as a substrate.