Environmental Engineering Reference
In-Depth Information
The potential production costs of four silvicultural regimes for
Populus
,
Salix
,
Pinus
, and
Eucalyptus
considered the costs of cultivation, harvest, and soil use, yields expected at each site,
and the energy value of biomass (Faundez 2003).
Populus
and
Salix
grow quickly and have been
widely used for bioenergy, whereas
Pinus
and
Eucalyptus
plantations occupy >2 million ha in cen-
tral Chile. Because of a nonlinear relationship between soil use cost and productivity, the minimum
costs for both nonintensive
Pinus
and
Eucalyptus
regimes were for high productivity sites (more
expensive land), whereas for both intensive
Populus
and
Salix
regimes, the minimum costs were
for low productivity sites (less expensive land). Minimum costs of production of the nonintensive
regimes of 0.0355-0.1662UF/GJ for
Eucalyptus
and 0.0626-0.3822 UF/GJ for
Pinus
were at most
one-half those of the intensive regimes of 0.1201-0.1325 UF/GJ for
Populus
and 0.1387- 0.1503 UF/
GJ for
Salix
, which were fairly insensitive to site productivity.
Given the large area of land available in central Chile for nonintensive compared to intensive for-
estry and the broad experience with nonintensive
Pinus
and
Eucalyptus
, these regimes appear best
(Faundez 2003). Because their energy production costs were comparable to those for oil and natural
gas, forest bioenergy could be a feasible alternative to fossil fuels and a way to avoid CO2 emissions.
If forests are to be used for bioenergy in Chile, selection of appropriate clones and species will be
essential for increasing productivity.
Jack pine SRWC production in Wisconsin peaked at age 5 in the densest planting and pro-
gressively later in more open spacings (Zavitkovski and Dawson 1978). Biomass production
was two or more times higher than in plantations grown under traditional silvicultural systems.
For 10-year-old irrigated, intensively cultured plantations in northern Wisconsin, energy inputs
(site preparation, fertilization, weed control, irrigation, harvesting, chipping, and drying) were
approximately 20% of the total energy (Zavitkovski 1979). The net energy of 1863 MBtu/ha,
equivalent to 340 barrels of oil, was 13% more energy than reported for highly productive, non-
irrigated, intensively cultured stands in eastern United States. Net energy returns were linearly
and positively correlated with energy invested in both irrigated and nonirrigated, intensively
cultured plantations and a naturally regenerated forest, indicating that intensive culture brings
commensurate returns.
In association with fire hazard reduction policies, forest biomass from extensive natural pine
forests, such as in northern California, southwestern Oregon, and Oregon east of the Cascade
Mountains, can fuel power plants (Barbour et al. 2008). For three hazard reduction scenarios,
the mix of species and sizes removed was similar, and average yields were quite high. Sawlogs
were 67 to 79% of the weight removed. Tops and limbs of commercial species >25.4 cm DBH and
noncommercial species provided most of the biomass chips. Low value conifers (17.8 to 40.6 cm
DBH) were also an important biomass source, whereas trees <17.8 cm DBH were a relatively minor
component. To pay for fire hazard reduction treatments, 9.1 to 18.2 mt/ha of sawlogs plus perhaps
a quarter of that in biomass chips need to be removed. Considerable emphasis has been placed on
finding uses for small trees (USDA FS 2005; USDE and USDA 2005). Fire hazard reduction treat-
ments could provide enough raw materials to fuel one or more 20 MW wood-fired electrical power
generation plants.
In arid and semiarid Mediterranean regions,
P. halepensis
and other pines are potential bio-
energy sources. For example, Catalonia in northeast Spain has 12,146 km
2
of forests (38% of
Catalonia, 10% of Spain's forests) composed primarily of
Quercus ilex
,
P. sylvestris
,
P. halepen-
sis
and
P. nigra
(Puy et al. 2008). The Catalan Energy Plan 2006-2015 estimates 197% more
forest and agricultural biomass consumption, mainly as heating for household and industrial uses,
such as sawmills. Catalonia's biomass potential of forest, agricultural, and sawmill residues, and
other bulky wastes is approximately 2.6 million tons, approximately 1 Mtoe. If forest biomass
is to be an important bioenergy source in Mediterranean countries, key factors are property
regimes, low productivity, weak institutional capacity, logistics and supply difficulties, and forest
product profitability. Technological solutions alone do not guarantee a prominent role for forest
biomass in southern Europe.
