https://doi.org/10.3390/en16010509
“Interest in biomass has increased due to current environmental issues, and biomass analysis is usually performed using element and proximate analyses to ascertain its fuel characteristics. Mainly, element component prediction models have been developed based on proximate analysis, yet few studies have predicted proximate components based on element analysis. Hence, this study developed a proximate component prediction model following the calorific value calculation. Analysis of Pearson’s correlation coefficient showed that volatile matter (VM) and fixed carbon (FC) were positively correlated with hydrogen and oxygen, and with carbon, respectively. Thus, the model correlation was developed using a combination of the “stepwise” and “enter” methods along with linear or nonlinear regressions. The optimal models were developed for VM and ash content (Ash). The VM optimal model values were: R2 = 0.9402, root-mean-square error (RMSE) = 7.0063, average absolute error (AAE) = 14.8170%, and average bias error (ABE) = −11.7862%. For Ash, the values were: R2 = 0.9249, RMSE = 2.9614, AAE = 168.9028%, and ABE = 167.2849%, and for FC, the values were: R2 = 9505, RMSE = 6.3214, AAE = 18.3199%, and ABE = 15.0094%. This study provides a model to predict the proximate component by element analysis. Contrary to existing method, proximate analysis can be predicted based on elemental analysis, and shows that consume samples can be performed at once.”
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2.2. Element and Proximate Analyses
In this study, untreated pepper stem and samples of torrefied pepper stems at 200, 230, and 270 °C for 20, 30, and 40 min were analyzed. Based on the quality test method for solid fuel products stipulated by the Ministry of Environment in Korea [48], elemental analysis was conducted to determine the contents of the elements C, H, N, and S (FlashEA 1112, Thermo Fisher Scientific, MA, USA). The oxygen content was calculated as follows.
| C [%] |
H [%] |
N [%] |
O [%] |
S [%] |
VM [%] |
FC [%] |
Ash [%] |
Ref |
|---|---|---|---|---|---|---|---|---|
| 44.414 | 6.07 | 0.977 | 40.2 | 0 | 76 | 9.05 | 3.55 | This study |
| 45.241 | 5.514 | 0.858 | 31.007 | 0 | 75.1 | 13.09 | 3.61 | |
| 45.533 | 5.603 | 0.989 | 30.269 | 0 | 74.21 | 14.48 | 3.91 | |
| 45.222 | 5.928 | 1.001 | 30.132 | 0 | 73.9 | 15.73 | 6.61 | |
| 48.417 | 5.841 | 1.008 | 29.208 | 0 | 73.25 | 16.51 | 3.6 | |
| 50.262 | 5.549 | 1.034 | 30.726 | 0 | 72.27 | 18.42 | 3.68 | |
| 50.629 | 5.533 | 1.098 | 27.841 | 0 | 72.03 | 19.15 | 3.56 | |
| 54.011 | 5.501 | 1.08 | 24.995 | 0 | 67.9 | 23.6 | 3.98 | |
| 54.954 | 5.738 | 1.218 | 25.817 | 0 | 65.56 | 25.92 | 4.2 | |
| 55.038 | 5.492 | 0.927 | 25.474 | 0 | 65.36 | 26.53 | 3.96 | |
| 43.25 | 5.57 | 0.6 | 41.89 | 0 | 73.87 | 17.44 | 8.69 | [52] |
| 48.18 | 5.46 | 0.69 | 36.2 | 0 | 71.53 | 19 | 9.47 | |
| 55.03 | 4.97 | 0.82 | 28.63 | 0 | 62.59 | 26.86 | 10.55 | |
| 61.7 | 4.19 | 0.94 | 21.88 | 0 | 45.45 | 43.26 | 11.29 | |
| 59.980 | 5.400 | 0.250 | 33.350 | 0 | 66.47 | 28.55 | 0.98 | [53] |
| 60.980 | 5.100 | 0.210 | 32.690 | 0 | 62.85 | 32.36 | 0.98 | |
| 63.440 | 5.100 | 0.180 | 30.720 | 0 | 65.71 | 30.24 | 0.54 | |
| 64.370 | 5.000 | 0.180 | 29.800 | 0 | 65.71 | 30.24 | 0.65 | |
| 51.910 | 6.100 | 0.100 | 41.000 | 0 | 69.80 | 18.20 | 0.74 | |
| 50.300 | 5.300 | 0.000 | 44.400 | 0 | 84.20 | 15.50 | 0.30 | [54] |
| 51.700 | 5.400 | 0.000 | 42.900 | 0 | 80.60 | 19.20 | 0.35 | |
| 54.400 | 5.200 | 0.000 | 40.400 | 0 | 75.70 | 24.20 | 0.40 | |
| 47.000 | 6.070 | 0.210 | 46.600 | 0.120 | 82.94 | 16.14 | 0.92 | [55] |
| 47.920 | 3.500 | 1.340 | 47.060 | 0.170 | 30.56 | 43.17 | 26.27 | |
| 58.430 | 3.010 | 1.020 | 37.380 | 0.160 | 20.82 | 57.19 | 21.99 | |
| 67.310 | 2.670 | 0.870 | 28.980 | 0.170 | 5.33 | 77.35 | 17.32 | |
| 74.080 | 2.500 | 0.500 | 22.740 | 0.170 | 4.72 | 83.25 | 12.03 | |
| 62.200 | 5.180 | 1.690 | 24.210 | 0 | 60.77 | 32.50 | 6.72 | [56] |
| 71.130 | 4.030 | 1.940 | 15.050 | 0 | 29.85 | 62.30 | 7.85 | |
| 74.880 | 2.880 | 1.770 | 10.410 | 0 | 23.19 | 66.75 | 10.06 | |
| 80.010 | 2.720 | 1.280 | 6.590 | 0 | 14.86 | 75.73 | 9.40 | |
| 45.150 | 5.150 | 0.750 | 42.920 | 0.140 | 75.55 | 18.58 | 5.87 | [57] |
| 71.340 | 3.930 | 1.430 | 10.840 | 0.240 | 27.06 | 62.72 | 12.22 | |
| 75.030 | 2.620 | 1.410 | 7.790 | 0.240 | 17.49 | 69.60 | 12.91 | |
| 78.480 | 1.880 | 1.530 | 3.940 | 0.320 | 11.49 | 74.66 | 13.85 | |
| 44.430 | 6.160 | 0.180 | 49.230 | 0 | 67.30 | 19.50 | 1.70 | [58] |
| 45.710 | 5.890 | 0.000 | 48.400 | 0 | 69.60 | 18.80 | 0.90 | |
| 79.970 | 3.530 | 0.010 | 16.490 | 0 | 32.10 | 60.00 | 3.10 | |
| 79.820 | 3.550 | 0.010 | 16.620 | 0 | 29.20 | 61.30 | 4.80 | |
| 77.480 | 3.640 | 0.100 | 18.780 | 0 | 25.00 | 69.10 | 2.00 | |
| 78.190 | 3.220 | 0.690 | 17.900 | 0 | 27.60 | 66.80 | 2.80 | |
| 76.950 | 3.320 | 0.740 | 18.899 | 0 | 26.10 | 68.10 | 1.00 | |
| 78.540 | 3.250 | 0.590 | 17.620 | 0 | 25.00 | 71.30 | 1.00 | |
| 46.370 | 6.290 | 46.790 | 0.550 | 0.110 | 83.46 | 14.26 | 2.17 | [59] |
| 41.920 | 4.210 | 53.640 | 0.230 | 0.100 | 71.18 | 26.94 | 1.77 | |
| 47.160 | 4.730 | 47.850 | 0.250 | 0.130 | 71.86 | 25.52 | 2.49 | |
| 52.700 | 3.800 | 43.220 | 0.280 | 0.140 | 62.19 | 34.46 | 3.22 | |
| 58.250 | 2.810 | 38.680 | 0.310 | 0.150 | 51.85 | 44.04 | 3.95 | |
| 45.650 | 5.120 | 39.630 | 1.660 | 0.920 | 73.94 | 14.39 | 7.020 | [60] |
| 58.040 | 4.280 | 18.790 | 2.750 | 0.870 | 43.82 | 37.21 | 15.270 | |
| 59.140 | 3.470 | 14.540 | 2.530 | 0.790 | 31.78 | 42.38 | 19.530 | |
| 62.590 | 3.360 | 9.910 | 2.510 | 0.770 | 21.12 | 51.78 | 20.860 | |
| 63.930 | 0.670 | 9.430 | 2.150 | 0.860 | 18.73 | 54.11 | 20.960 | |
| 63.830 | 1.650 | 9.330 | 2.110 | 0.630 | 17.83 | 54.07 | 22.390 | |
| 62.010 | 1.850 | 9.790 | 2.220 | 0.670 | 17.50 | 54.01 | 23.460 |
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