Bioenergy as a substitute for fossil energy is regarded a possibility to reduce the energy related carbon dioxide emissions to the atmosphere, because 'the carbon, which is set free from biomass combustion, is taken up again by regrowing plants and thus the carbon cycle of bioenergy is closed', as it is often argued. In a more detailed analysis of bioenergy strategies, two main effects have to be investigated: on the one hand, carbon in fossil fuels is substituted and thus not emitted to the atmosphere, while on the other hand, the use of biofuels might result in a reduction of carbon stored in the biosphere (plants, litter and soil). One of the possibilities to use biomass for energy is to burn logging residues from conventional forestry for heat and/or power production. For this type of bioenergy strategy, a model has been developed which allows one to calculate the change in carbon storage in three soil carbon pools and the carbon fluxes to and from these pools. The model results indicate that the carbon stored in the forest soil is reduced when logging residues are removed for bioenergy to displace fossil fuels. However, this effect is limited, as eventually a new equilibrium of carbon storage in the forest soil is reached, while fossil fuel substitution is continued further on. The time-dependent characteristic value 'carbon neutrality' (CN), which is the ratio of net emission reduction (fossil fuel substitution minus carbon losses of the soil) to the 'saved' carbon emissions from the substituted reference energy system, reflects this effect. CN equal to one means that bioenergy is completely 'CO2-neutral'. For bioenergy from logging residues, CN is very low at the beginning when bioenergy is introduced, increases continuously and approaches one at infinity. According to the results of parameter studies, CN of bioenergy from logging residues in temperate and boreal forests lies between 0.49 and 0.82 after 20 years and between 0.75 and 0.88 after 100 years.