Milled poplar wood (1.7 mm mesh size) was composted in lab-scale reactors. Initial C/N ratios were adjusted to 10:1, 30:1, and 50:1 using urea as the nitrogen source. At each C/N ratio, three moisture levels (30, 50, and 70%) were tested. C/N ratios of 50:1 or 30:1 and moisture content of 70% favored more effective composting as indicated by higher levels of mineralization of the poplar wood to CO2.