smaller (13.8 GJ/t). The reason is that in the current system, using
applied system boundaries, only few surplus wood is converted to
electricity.
The sensitivity of life-cycle CO2 emissions from paper production
(210 kgCO2/t paper) is presented in Fig. 11. The lowest CO2
emissions (−110 kgCO2/t paper) are found for minimum CO2 emission
factors for heat generation. The life-cycle CO2 emissions of
paper production could be reduced with 150% if all heat needed,
would be provided via CO2 neutral energy sources. Steam is nowadays
mainly provided via natural gas. CO2 emissions do not only
drop to 0, but even become negative due to CO2 credits at the endof-
paper life. The influence of CO2 emissions of reference electricity
production is smaller. A low emission factor for electricity production
leads to higher life-cycle CO2 emissions (320 kgCO2/t paper).
This is because energy extracted from biomass streams (e.g. via
black liquor) replaces energy produced by the grid.
In general, the sensitivity of life-cycle energy use of paper production
to the main energy conversion parameters is found to be
relatively small (