Introduction - Biomass Gasification, Pyrolysis and Torrefaction - page 16

dead tree could release more harmful CH 4 if it decomposes in water. The
use of a tree as fuel provides carbon-neutral energy while avoiding methane
gas release from decomposed deadwood. Careless use of trees for energy,
however, could spell environmental disaster. But a managed utilization with
fresh planting of trees following cutting, as is done by some pulp industries,
could sustain its use for energy in an environment-friendly way. Energy
plantation with fast-growing plants like Switchgrass and Miscanthus are
being considered as fuel for new energy projects. These plants have very
short growing periods that can be counted in months.

1.3.2 Environmental Benefits
With growing evidence of global warming, the dire need to reduce human-
made GHG emissions is being recognized. Also, emission of other air pollu-
tants, such as NO, SO 2 , and Hg, is no longer acceptable. From elementary
schools to corporate boardrooms, environment is a major issue, and it has
been a major driver for biomass use for energy production. Biomass has a
special appeal in this regard because, as explained below, it makes no net
contribution of carbon dioxide to the atmosphere. Regulations for making
biomass economically viable are in place in many countries. For example, if
biomass replaces fossil fuel in a power plant, that plant could earn credits for
CO 2 reduction equivalent to what the fossil fuel was emitting. These credits
can be sold on the market for additional revenue in countries where such
trades are in practice.

1.3.2.1 Carbon-Neutral Feature of Biomass
When burned, biomass releases the CO 2 it absorbed from the atmosphere in
the recent past, not millions of years ago, as is the case for fossil fuel. The
net addition of CO 2 to the atmosphere through biomass combustion is thus
considered to be zero. For this reason, biomass is considered a carbon-
neutral fuel. One may, however, argue that CO 2 is released for harvesting,
transporting, processing biomass, but that indirect emission is common for
fossil fuels which has emissions from mining, transporting, and preparation
of fossil fuel. A life cycle analysis that compares release of CO 2 from all
direct and indirect actions shows that biomass is a clear winner over fossil
fuel in this respect.
Even if one leaves aside the carbon-neutral aspect of biomass, the carbon
intensity (amount of CO 2 released per unit energy production, g/kWhe) of
biomass (35

49 g/kWhe) is much lower than that of fossil fuels like coal as
the former is a low C/H ratio fuel (Weisser, D, 2007).
The CO 2 emission from gasification-based power plants is slightly less
than that from a combustion power plant on a unit heat release basis. For
example, emission from an integrated gasification combined cycle (IGCC)