BIOMASS COMPOSITION, PROPERTIES, AND CHARACTERIZATION - Biomass as a Sustainable Energy Source for the Future - page 39

1.8

Biomass

1.6

Peat

1.4

Lignite

1.2

Coal

Wood
Lignin
Cellulose

1.0

0.8

0.6

0.4

Increased heating value

0.2

Anthracite

0 0.2 0.4

Atomic O/C ratio

0.6 0.8

FIGURE 2.1 Van Krevelen diagram characterizing the coalification process. (Source:
Reproduced with permission from Prins et al. (2007). © Elsevier.)

This process first forms peat, subsequently lignites and subbituminous coals, then
bituminous coals, and finally anthracites, the most carbon-rich end stage. During this
coalification process, the heating value of the organic material gradually increases.
Table 2.3 presents an overview of fuels from young biomass to highly coalified
anthracite based on their proximate analysis, which determines the percentages of
moisture, volatile matter (VM), fixed carbon (FC), and ash, and ultimate analysis
(or elemental analysis), which determines the main elemental composition (C, H, O, N).
These analysis methods are discussed in Section 2.5. The data show that biogenic
sources are already heterogeneous with respect to the main elements in the fuel. Some
biomasses, such as sewage sludge andmeat and bonemeal (MBM), have lower oxygen
contents on a dry fuel basis mainly due to their high ash contents.
As the table shows, there is a wide variety in the chemical composition among
biomass species. The natural biomass composition is impacted by the following main
aspects (see also Vassilev et al., 2010 and references therein):

1. Biomass type, species, or specific plant part; growth characteristics; uptake of
certain compounds from the environment (air/water/soil); and their transport to
and deposition in dedicated parts of the plant
2. External conditions of biomass growth with particular roles of:
a. Sunlight
b. Climate, including seasonal fluctuations
c. Soil type
d. Water availability
e. pH