3.2 Elemental and combustion analysis
The elemental analysis of the dried biomass samples in percentages ofC , H , N , and O were determined to give an empirical formula representing the energy constituent of the biomass. Phosphorus and sulphur are not normally included because they do not play any important role in the material balance of cellular reactions and their oxides are part of the ash formed on combustion, thus they are ignored in empirical formulation [17]. The empirical formula of the biomass containing a unit carbon for BA, BCN and GA samples are\(CH_{2.377}N_{0.091}O_{1.093}\), \(CH_{1.82}N_{0.027}O_{0.804}\), and\(CH_{1.167}N_{0.067}O_{0.558}\) , with molecular weight of 33.14, 27.06 and 23.03 g/C-mol, respectively [26] which aligns with the previous report for dry biomass[24, 25]. The enthalpy of combustion\(({H}_{C}^{o})\) of dry biomass in bomb calorimeter is presented in Table 4 based on the reactions (5), (6) and (7) below:
\(BA:CH_{2.377}N_{0.091}O_{1.093}\left(\text{cell}\right)+1.048O_{2(g)}\rightarrow\text{CO}_{2(g)}+1.189H_{2}O_{(l)}+0.046N_{2(g)}\)(5)
\(BCN:CH_{1.82}N_{0.027}O_{0.804}\left(\text{cell}\right)+1.053O_{2(g)}\rightarrow\text{CO}_{2(g)}+0.91H_{2}O_{(l)}+0.0135N_{2(g)}\)(6)
\(GA:\ CH_{1.167}N_{0.067}O_{0.558}\left(\text{cell}\right)+1.0127O_{2(g)}\rightarrow\text{CO}_{2(g)}+0.5835H_{2}O_{(l)}+0.0335N_{2(g)}\)(7)
Table 4: Enthalpy of combustion and formation of dry biomass at 298.15 K and 1 atm.