Page 271 - Synthetic Fuels Handbook

FUELS FROM BIOMASS 257

A final issue, perhaps of greater concern to policymakers, is that deployment on a
large scale is required to gain necessary economies of scale for most of these processes,
where the cost of syngas production can easily be more than 50 percent of the total process
cost. This requirement for large facilities raises the level of capital required for infrastruc-
ture development, increasing risk to the investor; it also increases the amount of biomass
required for operation, which makes it more difficult to supply the facility over the course
of its operational lifetime.
One of the major implications of the thermal-based process option scenarios is the abil-
ity to generate excess heat and power. Self-generation of heat and power by the combustion
of a portion of biomass feedstock can offset fossil fuel requirements, displacing the load on
utilities and improve the environmental performance of the facility. Especially, since the
cost of buying natural gas to generate heat and power internally has risen dramatically.
Other options for improved energy production include co-firing or cogeneration (i.e.,
combining biomass with fossil fuels in combustion). It is estimated that gasification tech-
nology has the potential to generate twice as much electricity per ton of black liquor as a
conventional recovery boiler. This additional power can reduce the need to purchase natural
gas, coal, oil, and electricity for everyday operations, increasing the economic performance
of the facility.
Excess heat and power can be utilized for additional value-added processing, or can
be distributed through a local network to provide district heating of nearby businesses and
residences. The potential appeal of bioenergy as a product may be limited, however, by the
regulatory regime which governs electricity generation, transmission, and sales.

8.6.3 Greenhouse Gas Production

Greenhouse gas production associated with lignocellulosic-based feedstocks is anticipated to
be much lower than with conventional fuels. The environmental performance depends very
much on the specific life cycle of the fuel, including the country in which the life cycle assess-
ment was conducted, the feedstock on which the fuel is based, the vehicle used, the propulsion
system, and the overall state of technology (Quirin et al., 2004; VIEWLS, 2005).
In general, fuels (and chemicals) made from lignocellulosic materials are characterized
by reduced carbon dioxide emissions when compared to similar products derived from
petroleum. Most biofuels can reduce greenhouse gas emissions significantly and substitut-
ing emissions by utilizing bio-based energy can create an overall negative emission for the
fuel (VIEWLS, 2005).
Fischer-Tropsch fuels based on bio-residues are likely to have the lowest possible emis-
sions; this is typical of diesel propulsion systems that have better energy recovery. If energy
crops are utilized as a feedstock, the overall emissions rise slightly, because the benefit of
residue disposal is lost. Ethanol from residues or from energy crops also have relatively low
emissions, particularly compared to conventional fuels including gasoline and diesel fuel.
For ethanol from lignocellulose, there is a potential to reduce greenhouse has emissions
with improved technology. This reflects the close-to-commercial status of the technology
today, and the anticipated improvements that will be seen as this technology improves. For
Fischer-Tropsch fuels, it is anticipated that commercial status will not be achieved until
post-2010 (Mabee and Saddler, 2006).

8.6.4 Other Aspects

For example, a biorefinery using lignin as a feedstock would produce a range of valuable
organic chemicals and liquid fuels that, at the present time, could supplement or even