# Biochar from Agro-Forest Residue: Application Perspective Based on Decision Support Analysis
## 4 Conclusions  
In the present research, biochar was produced from six different types of biomass in a laboratory-scale reactor of type HTF, in nitrogen, at a residence time of one hour, atmospheric pressure, and at mild temperature conditions (500 \({}^{\circ}\)C). Based on the experimentally measured physical and chemical features of the derived biochar, a decision-supporting tool was applied, focused on its potential role/application as biofuel, catalyst, CO\({}_{2}\) sequestration, and soil amendment, and as supercapacitor. The general results can be summarized as follows: (i) The effect of feedstock on biochar yield allowed to deduce a direct proportionality for the biomass lignin content and the biochar yield, e.g., the biomass having the highest lignin content--grape pomace (49.62%), showed the highest mass yield (35.07%) of biochar and vice versa for the colza and softwood. The highest HHV were obtained for the same three types of biomass (grape pomace 21.20; peach stones 22.36; cherry stones 23.62 MJ/kg) and derived biochar (grape pomace 28.11; peach stones 28.62; cherry stones 33.34 MJ/kg). As expected, the opposite was observed proportionality for the content of volatiles and fixed carbon in char, in comparison to biomass feedstock; (ii) Biochar thermal decomposition showed similar dependence on the feedstock constituents: cellulose, hemicellulose, and lignin. Two general stages were identified from the TGA/DTG analysis of biochar in air: devolatilization (stage 2)--between 180 and 560 \({}^{\circ}\)C, and oxidation (stage 3)--between560 and 720 \({}^{\circ}\)C, accompanied by a slight shift to the higher temperatures with an increase in heating rate. The kinetic analysis confirmed that the activation energy of biochar oxidation, obtained for the devolatilization (stage 2), decreased when increasing the heating rate, except for colza and cherry stones, while during char combustion (stage 3), the opposite tendency was observed--except for cherry stones and grape pomace; (iii) Generally, all types of biochar showed considerably lower H/C and O/C ratios in comparison to biomass, thus increasing their thermal stability. The results proposed the potential use of biochar as renewable energy carriers; (iv) The SEM images showed satisfactory porosity of the particle surface, which coincided with the Specific surface area (m\({}^{2}\)/g), \(S_{\text{BET}}\), estimated from biochar CO\({}_{2}\) adsorption; (v) The experimentally measured EC and total salt content widely varied (EC from 56 to 1015 \(\upmu\)S/cm; salt content between 28 and 980 ppm), which along with the alkaline pH (8.38-11.08) suggested further possible biochar applications as a valuable additive, enhancing the efficiency of different energy recovery technologies or even soil amendment. Biochar particular characteristics, described in Section 3.4. and Section 3.5, suggested the need of implementing a decision support analysis for determining the unrevealed application perspective of the obtained biochar; (vi) The decision support analysis showed that grape pomace, peach stones, and cherry stones achieved the most promising results for all tested applications (as biofuel, catalyst, CO\({}_{2}\) sequestration and soil amendment, and supercapacitor) comparatively to colza, softwood, and sunflower husks. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13053240/s1](https://www.mdpi.com/article/10.3390/app13053240/s1)]([https://www.mdpi.com/article/10.3390/app13053240/s1](https://www.mdpi.com/article/10.3390/app13053240/s1)), Table S1: Decision support analysis for biofuel application; Table S2: Decision support analysis for catalyst application; Table S3: Decision support analysis for CO\({}_{2}\) sequestration and soil amendment process application; Table S4: Decision support analysis for supercapacitor process application. T.P. : experimental work, results analysis and visualization, writing and editing original draft; I.N.