Page 26 - Advances in bioenergy the sustainability challenge

associated with the expansion of selected biofuel/crop combinations. The studies are
reported with LUC emissions amortized over 30 years of production for comparison.
(Reprinted with permission from Ref 35. Copyright 2011, IEA Bioenergy.)

Figure 16.5 Accumulated net GHG savings in four biofuel scenarios. The green
‘Biofuel use’ bars show GHG savings (positive) from biofuel replacement of gasoline
and diesel; the red ‘Land use change’ bars show GHG emissions (negative) caused by
dLUC and iLUC; and the blue ‘Net GHG balance’ bars show the result of subtracting
the LUC emissions from ‘Biofuel use’ savings. WEO has regional biofuel use up to
2030 as projected by the IEA World Energy Outlook 2008 reference scenario and 2nd
generation biofuels are gradually deployed after 2015. TAR has roughly twice as high
biofuel use as WEO and faster deployment of 2nd generation biofuels. The vP
scenarios have higher agricultural productivity growth in developing countries leading

to lower LUC. (Reprinted with permission from Refs 35 and 117. Copyright 2011 and
2009, IEA Bioenergy.)

Figure 16.6 Historic overview of gross felling (1853–2003) and–-placed behind the
area showing gross felling—annual increment (1926–2003) in the Swedish forest. The
method of estimating felling changed between 1945 and 1955, resulting in two
overlapping curves (Ref 125). (Reprinted with permission from Ref 126. Copyright
2010, Peter Eliasson.)

Figure 16.7 Effects on the C balance of increased removal of felling residues in a
Norway spruce forest in south Sweden. In the ‘Stems Only’ scenario, harvest residues
are left on the ground both after thinning and final felling. The ‘Stems & GROT’
scenario involves extraction of 80% of the logging residue after thinning and final
felling (GROT is the Swedish acronym for branches and tops—GRenar Och Toppar in
Swedish), and the ‘Stems, GROT & Stumps’ scenario includes in addition the removal
of 50% of stumps-coarse root systems at final felling. The increased residue removal
continues over the whole 300-year period. Upper panes show the amount of removal in

comparison to the ‘Stems Only’ scenario and lower panes the corresponding variation
in soil C. Single stands are plotted behind the landscape averages in the foreground.
The sharp declines in stand level soil carbon shown at each harvest occasion are
caused by the removal of residues, reducing litter addition to soil C. (Reprinted with
permission from Ref 127. Copyright 2011, Peter Eliasson.)

Figure 16.8 Tree biomass in a chronosequence of 100 identical simulations of Norway
spruce stands, illustrating the difference between stand level and landscape level
dynamics in a forest in southern Sweden. The assumed management resembles the
dominant management regime during the previous decades, i.e., only stem wood has
been removed at harvests, and thinning has been done at intervals prescribed by the
Swedish Forest Agency. The stand is thinned three times (year 33, 48, and 65, with
biomass harvest corresponding to about one-fourth of the basal area) and final harvest
takes place after 100 years where only stems are removed. It is assumed that 10% of
the stem biomass is left as harvest residue (tops). Each stand is planted 1 year after the