Carbon emissions accounting with forest-derived biomass energy is more complex than for waste or crop-residue biomass because carbon emissions and uptake occur over more heterogeneous landscapes and longer timeframes. To better understand climate impacts of forest bioenergy use, we develop a comprehensive framework for assessing the dynamic lifecycle greenhouse gas emissions for bioenergy projects using pine pulpwood feedstocks from managed forests in the U.S. South. We apply it in eight different forest basins to determine the carbon payback period and cumulative carbon storage for hypothetical bioenergy projects with 30-year plant operating lives (2030-2060). Variations in local forest types, age class distributions, and traditional wood product market demands result in large differences in carbon payback times between basins. In general, carbon debt repayment is faster for biofuel or bioelectricity projects that employ CCS than those that do not. We find that facilities employing CCS and consuming 3 million green tons of feedstock annually yield carbon payback periods below 10 years if located within pine-dominated coastal plain or gulf coast regions. In a hardwood-dominated basin such as in Virginia, carbon payback is not achieved.