Ahmad, AdriantoKhairatMailinda, Tirta2014-03-102014-03-102014-03-101693-4393wahyu sari yenihttp://repository.unri.ac.id/xmlui/handle/123456789/5821Production of CPO in Indonesia continues increase with increasing amount of palm oil’s production. Along with increased production of palm oil, the amount of waste generated has also increased, one of them is oil palm mesocarp fiber. The largest component in oil palm mesocarp fiber is cellulose, hemicellulose, lignin and small amounts of compounds of N, P and micro nutrients, so that potential to be processed into compost. This research objective was to determine the influence of nitrogen concentration in composting process and determine the duration of the composting process oil palm mesocarp fiber. Stages of this research include the preparation of starter, substrate preparation, preparation of bioreactor, and the composting process. Composting method used is windrow aerobic system. The composting process takes place by adding a mixed culture as a starter with concentration 30% and adding urea as nitrogen source by varying the nitrogen concentration 0%, 0.5%, 1%, 1.5%, and 2%. Parameters observed in this study were water content, pH, temperature, levels of C, N and ratio C / N. The results of this study indicate that the addition of nitrogen concentration can speed up the composting process. The optimum concentration of nitrogen obtained on nitrogen concentration of 1.5% on day 40 with C / N ratio of 14.29.enCompostConcentration of nitrogenOil palm mesocarp fiberUR-Scientific Work Lecturer