INTRODUCTION: SOCIOECONOMIC ASPECTS OF BIOMASS CONVERSION - Biomass as a Sustainable Energy Source for the Future - page 24

1.3.2.1 Direct Land Use Change Direct land use change (dLUC) is the case when
other biomass is grown on land that was previously forest or other high carbon stock
land. This may lead to a (usually negative) change in the soil carbon content. The
impact of such a change is still comparatively straightforward when considering
the next form of LUC.

1.3.2.2 Indirect Land Use Change Indirect land use change (iLUC) occurs when
farmers start to grow certain biomass on a land with the purpose of being taken up in a
bioenergy supply chain, but with an associated displacement of, e.g., food production
that then is started on land elsewhere where forest or other high carbon stock land is
converted to arable land. Considerable debate exists among scientists about the extent
of the impact of iLUC on GHG emissions.
When biomass is grown for energy supply on purpose, it should not compete with
food, feed, and fiber production; therefore, cultivation on lower-quality lands with
comparatively low carbon stock is advisable. One can distinguish the following such
land types (Kampman et al., 2010):

￿ Marginal land: this is a land that is currently not cultivated as cropland. Although

it is technically feasible to produce crops, its yields are too low and costs too high
for competitive agricultural practice.

￿ Degraded land: this is a land that has been cultivated in the past but has become

marginal due to degradation of its soil, erosion, or other causes as a consequence
of inappropriate management or external factors such as climate change.

￿ Abandoned land: this is a degraded land with low productivity and a land with

high productivity that is currently not in use.

Figure 1.8 illustrates the difference between dLUC and iLUC.

1.3.2.3 Upfront Carbon Debt Creation Linked to the issue of LUC is the point of
establishing carbon debt for different scenarios of biomass growth for energy supply.
The assumption that the use of bioenergy always

results in zero GHG emissions, i.e., that use of biomass is always carbon neutral
regardless of the time horizon considered, is incorrect. Land clearing usually leads
to CO 2 -equivalent emissions that create a carbon loss from the beginning, the so-
called upfront carbon debt creation. It is clear that all sources of woody bioenergy
(replacing fossil energy) from sustainably managed forests will result in emission
reductions in the long term, but diverse bioenergy sources have various impacts
on the short-medium term. Therefore, some sources of wood for the generation of
bioenergy do not contribute to reducing GHG emissions within the time frame of
climate mitigation policies, whereas other sources may have this potential (Zanchi
et al., 2012).

— often widely taken for granted —