FULL FUEL-CYCLE CARBON BALANCES OF BIOENERGY AND FORESTRY OPTIONS

Forestry projects can - at least temporarily - mitigate the net flux o f anthropogenic CO2 to the atmosphere by removing C from the atmospher e and sequestering it in growing trees. The net flux of C to the atmos phere can also be reduced if trees are burned to displace the burning of fossil fuels and are then replanted to recycle the C back into the biosphere, or if wood is used for products that store carbon and are o therwise made from other, more energy-intensive materials. A computer model is employed to calculate carbon balances of two land management and biomass utilization scenarios - conventional forest management and short-rotation forestry. Sensitivity analyses reveal that the most im portant site and system dependent parameters for the net reduction of carbon emissions are the site occupancy prior to the project, growth r ate, efficiency of biomass conversion into energy and non-energy produ cts, and carbon emission rates and efficiencies of displaced fossil fu el cycles. The results demonstrate that time is another important cons ideration and that projects can look considerably different, in terms of C balance, when the endpoint of the analysis is 20, 50, or 100 year s.