Page 320 - Synthetic Fuels Handbook

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of wood fuel used for on-site heat and power production by 2010, and increase the share of
wood in its on-site total primary energy consumption from 49 to 56 percent. In other words,
energy will be the main product of the forests, and energy and environmental policies which
have been enacted present new opportunities for its further development. A combination of
factors such as higher oil prices and technological developments in wood fuel production,
transportation, and combustion is also making wood fuels more attractive.
The dynamics of wood fuel flows are complex and very site-specific. The development
of sustainable wood energy systems remains one of the most critical issues to be addressed
by policy makers and community planners. With society giving increasing attention to sus-
tainability issues, in the case of wood energy in both developing and developed countries,
economical, environmental, and social issues deserve particular attention.
Most of the uses of wood are accounted for by combustion in intermediate or large-scale
units outside the forest industries (e.g., in schools, hospitals, barracks, or district-heating plants),
with minor volumes going to the production of charcoal. Very small volumes were used in a
few European countries to generate electricity or to manufacture solid fuels (e.g., briquettes).
No wood is used at present in the region to make synthetic liquid or gaseous fuels. Use of
energy wood by the forest industries and users has grown faster than use by households.
The technical platform chosen for biofuel production is determined in part by the charac-
teristics of the biomass available for processing. The majority of terrestrial biomass available is
typically derived from agricultural plants and from wood grown in forests, as well as from waste
residues generated in the processing or use of these resources. Currently, the primary barrier to
utilizing this biomass is generally recognized to be the lack of low-cost processing options capable
of converting these polymers into recoverable base chemical components (Lynd et al., 1999).
In the United States, much of the biomass being used for first-generation biofuel produc-
tion includes agricultural crops that are rich in sugars and starch. Because of the prevalence
of these feedstocks, the majority of activity toward developing new products has focused on
the bioconversion platform (BRDTAC, 2002a). Bioconversion isolates sugars from biomass,
which can then be processed into value-added products. Native sugars found in sugarcane and
sugar beet can be easily derived from these plants, and refined in facilities that require the low-
est level of capital input. Starch, a storage molecule which is a dominant component of cereal
crops such as corn and wheat, is comprised wholly of glucose. Starch may be subjected to an
additional processing in the form of an acid- or enzyme-catalyzed hydrolysis step to liberate
glucose using a single family of enzymes, the amylases, which makes bioconversion relatively
simple. Downstream processing of sugars includes traditional fermentation, which uses yeast
to produce ethanol; other types of fermentation, including bacterial fermentation under aerobic
and anaerobic conditions, can produce a variety of other products from the sugar stream.
In order to incorporate all aspects of biofuel production, including the value of coproducts
and the potential of the industry to diversify their product offering, we employ the biorefinery
concept. The biorefinery concept is important because it offers many potential environment-,
economy-, and security-related benefits to our society. Biorefineries provide the option of copro-
ducing high-value, low-volume products for niche markets together with lower-value commod-
ity products, such as industrial platform chemicals, fuels, or energy, which offsets the higher
costs that are associated with processing lignocellulose (Keller 1996, BRDTAC 2002b).

10.4 FUELS FROM WOOD

Energy from wood can come in several forms. There are three options currently available
for producing heat from wood: (a) logs, (b) woodchips, and (c) reconstituted fuels such as
pellets and briquettes. Other options which are at the research stage include liquid fuels
produced from wood and bales of compressed forest residues.