4.5.3. Global Scenarios for Biomass Energy
Recent scenario studies (Hall et al., 2000) show biomass energy contributing
150-200 EJ yr-1 by 2050, avoiding CO2 emissions of ~3.5 Gt C yr-1-more than
half of present fossil fuel emissions. Previous global energy scenarios show
a rising trend for biofuel use, at small or no additional cost, with Latin America
and Africa becoming large net exporters of liquid biofuels. WEC (1993) projects
62 EJ in 2020, plus traditional wood fuel in developing countries; IEA (1998)
projects that biomass fuels will grow at 1.2 percent per year to 60 EJ in 2020;
Lazarus et al. (1993) project 91 EJ in 2030; Dupont-Roc et al.
(1996) showed a business-as-usual scenario for Shell International with 221
EJ-of which 179 EJ were from fuel plantations-in 2060. The Global Energy Perspectives'
high-growth, high-biomass scenario has 316 EJ of biomass by 2100 (Nakicenovic
et al., 1998). Without arguing these and other numerical scenarios, the
common vision is that there is a large and increasing potential for biofuels
(see Fact Sheet 4.21 for land-use implications).
Under its Biofuel Activity Program, the International Energy Agency (IEA) monitors
a wide range of commercial and near-commercial processes, many of which use
small-scale plants for converting biofuel into heat, light, and transportation
fuels (Overend and Chornet, 1999; Rosillo-Calle et al., 2000). Walter
(2000) reviews new technology. Large sunk costs in long-lived capital stock
and infrastructure impedes market entry for renewable energy. Biofuel is relatively
compatible, however, with the fossil fuel-based energy systems (e.g., blending
with petroleum products, wood chips with coal at power stations). Modern biofuel
is efficient at small scales (e.g., in rural areas and developing countries).
4.5.4. Land Availability
In general, land availability (out of the very large area that might be used)
will be influenced by its value (opportunity cost) in the variety of services
that land provides, from wilderness through food production to urban occupation,
as well as by its biomass productivity. The potential for increased production
of biofuels can be accomplished through increased use of existing forest and
other land resources, higher rates of plant productivity, and more efficient
conversion processes and capture of wastes.
Unmanaged woody species have yields of less than 5 t ha-1 yr-1 (dry weight
biomass). Optimal management and planting of selected species and clones on
appropriate soils currently achieves 10-15 t ha-1 yr-1 in temperate areas and
15-25 t C ha-1 yr-1 in the tropics; 40 t C ha yr-1 has been obtained with Eucalyptus
in Brazil and Ethiopia. High yields (30-40 dry t ha-1 yr-1) are also possible
with herbaceous crops such as switchgrass (Hall et al., 1992). In Brazil, the
average annual yield of sugar cane has risen from 28 to 39 t ha-1 yr-1 (dry
weight) over 15 years, with more than 70 t ha-1 yr-1 achieved in Hawaii, southern
Africa, and Queensland (FAO, 1999).
There are large areas of deforested and degraded lands in tropical countries
that could produce multiple benefits from the establishment of biofuel plantations
(Brown, 1998). Conversion of these and other lands to biofuel plantations can
provide economic value to the local people. Large-scale biofuel production will
require specific energy crops, improved land management, species selection and
mixes, genetic engineering, and so forth.