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FAO/UNEP/UN-Energy Bioenergy Decision Support Tool -
MODULE 5: Land Resources
LAND USE AND NUTRIENTS
It is important to assess land use requirements in their broader
context, including hybrid measures of effciency or intensity. One
major land use concern that arises is the depletion of nutrients,
due to the large scale of bioenergy feedstocks and reliance on
intensive cultivation using dedicated monocultures. Consequently,
one metric of interest is the use of key nutrients per unit of
energy. As nitrogen is a key nutrient with signifcant environmental
impacts, the nitrogen intensity provides a useful metric that can
be compared alongside LUI; by combining the two measures,
one obtains a better indicator for sustainability. The two measures
can then be applied equally to biomass sources, regardless of
whether the source is woody, agricultural or algae.
Table 2 provides an example of analysis that combines both
metrics to create a combined ranking, with equal weighting given
to land use and nitrogen use intensity (Miller 2009). An obvious
conclusion from this comparison is that soybean, rapeseed and
grain sorghum are highly ineffcient crops for biofuel production
compared to almost any other option. Sugar cane scores highest
in the initial ranking and this held true even when sensitivity
analysis was conducted for key parameters such as higher
heating value (HHV), nitrogen and harvestable yield (Miller 2009).
It is also interesting to note that biofuels from algae are touted for
their low land requirements, but the use of a hybrid measure as
this one can illustrate better the overall resource/land effciency
pattern.
LAND USE COMPETITION
As the demand for food, feed, fbre, energy and other products
requiring signifcant land use increases, we expect greater land
use competition, ceteris paribus. Furthermore, since land is also
valued for recreation, conservation, biodiversity and many other
uses, the “productive” capacity of land must also be weighed
against ecosystem services that are in fact highly productive but
whose value is poorly refected in our socio-economic systems.
Consequently, the rise in importance of bioenergy has raised
concerns that other valuable land uses will suffer as a result of
bioenergy expansion. There are many different ways to reduce the
land use intensity and/or the associated impacts, such as better
use of co-products, improved agricultural breeding, landscape
ecology and integrated food-energy system
s
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.
Another possibility is the design of hybrid systems that comple-
ment each other in some way: one example is a hybrid wind/
biomass system that uses compressed air storage, which was
estimated to require 70 m2/MWh (Denholm, 2006), which is just a
fraction of the amount given for bioenergy in Table 2.
The attention paid to bioenergy systems has also led to increased
scrutiny of the land use effciency of agricultural and livestock
practices. Greater land use effciency in agriculture, forestry
and other land uses could free up some land for the renewable
energy options that are ultimately required to replace fossil and
nuclear fuels. Current agricultural practices have tended to be
land-intensive, as the low price of rural land in combination with
fossil-fuel infrastructure led to continual expansion. With precision
farming methods and low tillage methods, land can be used more
effectively while also reducing GHG impacts from fertilizer use,
N20 and soil carbon release; this is true regardless of whether the
China
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
Brazil
ASEAN
EU 27
India Other Asia SADC Other sub-
Saharan
Africa
United
States of
America
WORLD
Arable Land and Permenant Crops
Permenant Meadows and Pastures
Forest Area
Other Land
Figure 1: Land use per capita by type for selected regions or countries, 2008.
Source for land use data: FAOSTAT database, www.fao.org
1SADC includes the 14 countries of the Southern African Development Community
2ASEAN includes the 10 countries of the Association of Southeast Asian Nations (ASEAN)
3Arable land and permanent crops indicate current cultivation, but do not determine how much land is potentially cultivable.