Page 39 - Biomass Gasification, Pyrolysis And Torrefaction Practical Design and Theory

18 Biomass Gasification, Pyrolysis, and Torrefaction

1.3.2.3 Nitrogen Removal
A combustion system firing fossil fuels can oxidize the nitrogen in fuel and
combustion air into NO, the acid rain precursor, or into N 2 O, a GHG. Both
oxides are difficult to remove. In a gasification system, on the other hand,
nitrogen appears as either N 2 or NH 3 , which is removed relatively easily in
the syngas-cleaning stage.
Nitrous oxide emission results from the oxidation of fuel nitrogen alone.
Measurement in a biomass combustion system showed a relatively low level
of N 2 O emission (Van Loo and Koppejan, 2008, p. 295).

1.3.2.4 Dust and Hazardous Gases
Some speculate that highly toxic pollutants like dioxin and furan, which can
be released in a combustion system, are not likely to form in an oxygen-
starved gasifier. Particulate in the syngas is also reduced significantly by
multi stage gas cleanup systems, that include primary cyclone, scrubbers, gas
cooling, and acid gas-removal units. Together with these a gasification sys-
tem reduces the particulate emissions by one to two orders of magnitude
(Rezaiyan and Cheremisinoff, 2005).

1.3.3 Sociopolitical Benefits
The sociopolitical benefits of biomass use are substantial. For one, biomass
is a locally grown resource. For a biomass-based power plant to be economi-
cally viable, the biomass needs to come from within a limited radius from
the power plant. This means that every biomass plant can prompt the devel-
opment of associated industries for biomass growing, collecting, and trans-
porting. Some believe that a biomass fuel plant could create up to 20 times
more employment locally than that by a coal- or oil-based plant (Van Loo
and Koppejan, 2008, p. 1). The biomass industry thus has a positive impact
on the local economy.
Another very important aspect of biomass-based energy, fuel, or chemicals
is that they reduce reliance on imported fossil fuels giving a country added
benefit of energy independence. The global political landscape being volatile
has shown that the supply and price of fossil fuel can change dramatically
within a short time, with a sharp rise in the price of feedstock. Locally grown
biomass is relatively free from such uncertainties.

1.4 HISTORICAL BACKGROUND
The conversion of biomass into charcoal was perhaps the first large-scale
application of biomass conversion process. It has been used in India,
China and in the preindustrial era of Europe for extraction of iron from