Increasing petroleum prices and energy demand, serious concerns
about security of supply and environmental problems are
the major drivers in the search for alternative renewable energy
sources. Biomass is a primary candidate because of being the only
renewable source of fixed carbon, which is essential in the production
of conventional hydrocarbon liquid transportation fuels and
many consumer goods [1].
Biomass is a mixture of hemicellulose, cellulose, lignin and minor
amounts of other organics which each pyrolyses or degrades at
different rates and by various mechanisms and pathways. Lignin
decomposes over a wider temperature range compared to cellulose
and hemicellulose, which rapidly degrade over narrower temperature
ranges, hence the apparent thermal stability of lignin during
pyrolysis. The rate and extent of decomposition of each of these
components depends on the process parameters such reactor
(pyrolysis) temperature, biomass heating rate and pressure [2].
Fast pyrolysis, in which an effort is made to maximize the liquid
product yield from solid biomass, is a potential candidate for
power production. Fast pyrolysis is a high temperature process in
which biomass is rapidly heated in the absence of oxygen. As a result,
it decomposes to generate mostly vapors, aerosols and some
charcoal. Liquid production requires very low vapor residence time
to minimize secondary reactions of typically 1 s, although acceptable
yields can be obtained at residence times of up to 5 s if the vapor
temperature is kept below 773 K [3]. The bio-oil obtained from