Biomass Characteristics - Biomass Gasification, Pyrolysis and Torrefaction - page 47

Chapter 3
Biomass Characteristics
3.1 INTRODUCTION
The characteristics of biomass greatly influence the performance of a bio-
mass conversion system whether it is a combustor, torrefier, pyrolyzer, or
gasifier. A proper understanding of the physical and the chemical properties
of biomass feedstock is essential for the design of a reliable biomass conver-
sion system. This chapter discusses some important properties of biomass
that are relevant to such processes.
3.2 WHAT IS BIOMASS?
Biomass refers to any organic materials that are derived from plants or ani-
mals (Loppinet-Serani et al., 2008) that is living or was living in the recent
past. A universally accepted definition is difficult to find. However, the one
used by the United Nations Framework Convention on Climate Change
(UNFCCC, 2005) is relevant here:
[A] non-fossilized and biodegradable organic material originating from plants,
animals and micro-organisms. This shall also include products, by-products, residues
and waste from agriculture, forestry and related industries as well as the non-
fossilized and biodegradable organic fractions of industrial and municipal wastes.
Biomass also includes gases and liquids recovered from the decomposi-
tion of nonfossilized and biodegradable organic materials. In the United
States, there has been much debate on a legal definition. Appendix A gives a
recent legal interpretation of renewable biomass.
As a sustainable and renewable energy resource, biomass is constantly
being formed by the interaction of CO 2 , air, water, soil, and sunlight with
plants and animals. After an organism dies, microorganisms break down bio-
mass into constituent parts like H 2 O, CO 2 , and its potential energy. The car-
bon dioxide, a biomass releases through the action of microorganisms or
combustion, was absorbed by it in the recent past so, biomass combustion
does not add to the total CO 2 inventory of the Earth. It is thus called green-
house gas neutral or GHG neutral.
Biomass comes from botanical (plant species) or biological (animal waste
or carcass) sources, or from a combination of these. It thus includes only