Agronomy
2021, 11, 169
5 of 18
Content of S and Cl was determined by following the standard BS EN ISO 16994:2016 [
28
],
where S content was measured via the combustion method in the Sulphur add-on module
to the Elemental Determinator LECO CHN628 Series and the Cl content was determined
by the titrimetry technique.
O content was calculated by difference:
O
=
100
−
C
−
H
−
N
−
S
−
Cl
−
A
(5)
where: O—oxygen content on a dry basis, %; C—carbon content on a dry basis, %; H—
hydrogen content on a dry basis, %; N—nitrogen content on a dry basis, %; S—sulphur
content on a dry basis, %; C—chlorine content on a dry basis, %; A—ash content on a dry
basis, %.
Calorific Value. Calorific value was determined under the standard BS EN ISO
18125:2017 [
29
]. Around 1 g of the material compressed in an unbreakable test piece was
placed into the calorimeter IKA 6000 (IKA-Werke GmbH & Co. KG, Staufen, Germany),
which was configured with the required information such as sample weight, hydrogen
content, etc. Gross calorific value (GCV) was then measured automatically, and net calorific
value (NCV) was calculated according to the following equation:
Q
=
Q
gr
−
24.42
× (
M
+
8.94
×
H
)
(6)
where: Q—net calorific value, J
·
g
−1
; Q
gr
—gross calorific value, J
·
g
−1
; 24.42—coefficient
corresponding to 1% of the water from the sample at 25
◦
C; M—moisture content in the
sample, %; 8.94—coefficient for the conversion of hydrogen to the water; H—hydrogen
content in the sample, %.
2.4. Calculation of the Total Energy Yield
The equation for the energy potential/energy yield of residual biomass was designed
following the methodology of Akhmedov et al. [
30
]:
Ep
= (
T p
∗
k
) ∗
Q
(7)
where: Ep—annual energy potential of residual biomass, TJ; Tp—total annual grain/crop
production of country/region/province, t; k—constant/share of residual biomass or
residue ratio, where:
•
Constant for rice straw is 2.2, and it has been calculated as an average value of rice
straw residues according to previous studies [
15
,
31
];
•
Constant for rice husks is 0.2, the value was obtained from the previous studies [
15
,
32
];
•
Constant for sugarcane bagasse is 0.3, the value was gained from previous publica-
tions [
33
,
34
];
•
Constant for sugarcane trash is 0.2, the value was extracted from the previous stud-
ies [
35
,
36
].
Q—net calorific value of residual biomass as received*, TJ t
−1
.
* as the value for sugarcane trash was not tested in the laboratory within the frame of
this study, thus, the Q equal to 11.6 MJ kg
−1
(0.0116 TJ t
−1
) at moisture content 30% was
taken into consideration according to De Beer [
37
].
The obtained results of energy potential were also converted and expressed in another
unit, i.e., TWh as 1 TWh is equal to 3600 TJ.
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