Engineering Properties of Biomass - Engineering and Science of Biomass Feedstock Production and Provision - page 27

Japan) [ 42 , 49 ]. The black and white calibrations were performed before the
reflectance measurement. All measurements were made using an observer angle of
10° and a D65 illuminant. The 0 % color was calibrated with black and 100 % with
white standards. A sample of ground particle was spread out inside a Petri dish as
recommended by the instrument's operator manual. The color coordinates L * , a * ,
and b * (lightness, redness/greenness, and yellowness/blueness) were determined for
each sample. Five replicates of measurement were carried out.
The variation in color coordinates was calculated as the difference between the
measured values for L * , a * , and b * coordinates for the untreated and treated wood.
The differences were expressed in percentage of the initial value,

( )

* *

L - L

treated untreated

*

D L = 100 (2.8)

*

L

untreated

( )

* *

a - a

treated untreated

*

D a = 100 (2.9)

*

a

untreated

( )

* *

b - b

treated untreated

*

D b = 100 (2.10)

*

b

untreated

2.3 Recent Progress in Analyzing Biomass Engineering

Properties

2.3.1 Bulk Density, Particle Size, and Flowability

The bulk density and flowability of the biomass particles are highly influenced by
the particle size and shape. In most studies, the bulk density of a mixture of ground
particles from different sieves was measured [ 19 , 50 - 53 ]. Mani et al. (2004) reported
that the bulk and specific densities increase with the geometric particle diameter of
the particles at the same moisture content and developed second- or third-order
polynomial models relating the bulk and specific densities of agricultural biomass
grinds to their respective geometric particle diameter of the biomass grinds within
the range of 0.18-1.43 mm [ 50 ].
Sone's model was used to understand the compaction characteristics by tapping
of different biomass [ 51 ], and it was found that the chopped wheat straw particles
compacted very rapidly to reach the final tapped density as compared to the chopped
switchgrass and corn stover particles [ 52 ]. This result may be due to the low value
of Hausner ratio (i.e., the ratio of tapped density over the initial bulk density) of
chopped wheat straw particles and also its better flowability than the chopped
switchgrass and chopped corn stover. Tapping motion causes the particles to move
to each other to fill up the bulk pores in between the particles and rearrange their