Engineering Properties of Biomass - Engineering and Science of Biomass Feedstock Production and Provision - page 25

constantly in order to make sure the samples poured continuously and smoothly into
the funnel. The samples will flow through the funnel and form a heap with a conical
shape. Measurement of height ( H ) and radius ( R ) of the rest particles was taken five
times to determine the average value of angle of repose.
The height and radius of the semi-cone were measured and the angle of repose
( α ) was calculated from ( 2.7 ):

H
R

æ
ç

ö
÷

tan 1

-

a= (2.7)

where α is the static angle of repose (degree), H is the height (cm), and R is the
radius (cm).

2.2.4 Moisture Content

Moisture content of biomass is one of the important physical properties for the
design of a drying process [ 33 ]. Woody biomass is usually wet when collected from
the forest. It must be dried and processed to produce feedstock for heat and power
and chemical production. Dried biomass is also preferred during handling and stor-
age to minimize the mold formation [ 34 ], off-gassing [ 35 ], and self-heating issues
[ 36 , 37 ]. Drying kinetics of biomass for the dryer design is usually determined by
the accurate measurements of the moisture content of the biomass at different
intervals.
One of the standardized moisture content measurement methods for biomass is
described in the ASABE Standard S358.2 [ 38 ]. The procedure involves weighing
and drying about 100 g of pieces of biomass as received, in triplicate in a forced air
convection oven at 103 °C for 24 h to obtain the completely dry biomass. The dried
samples are cooled and weighed. A digital balance with 0.01-g precision is used for
the weighing procedure. The developed ISO standards are based on European stan-
dard CEN/TS 14774-3, which specifies 105 °C for 60 min for determination of
moisture content for solid biofuels [ 39 ]. The required mass of the small particles
with 1-mm geometric mean diameter is a few grams, while that for the large parti-
cles (e.g., wood chips) is 500 g.

2.2.5 Caloriic Value

Calorific value of biomass is crucial to determine its energy that can be recovered
during thermo-conversion. From recent studies, it was found that thermally treated
biomass with increased calorific value could be a suitable candidate to blend
and co-fire with coal for power generation with reduced greenhouse gas emissions
[ 40 - 45 ].