Table 1.
Physical and chemical properties of biochar (Yadav et al., 2023).
| Characteristics | Key-points |
|---|---|
| Porosity | The pore size of biochar changes on the basis of the material applied for biochar production and usually ranges from nano (<0.9 nm), micro (<2 nm), meso (2–50 nm) to macropores (>50 nm). |
| Surface functional groups | Different functional groups (e.g. hydroxyl-OH, amino-NH2, ketone-OR, ester -(C=O)OR, methyl-CH3, nitro-NO2, aldehyde-(C=O)H, carboxyl-(C=O)OH are shaped on biochar surface. |
| Carbon content | Biochar is greatly stable, consisting of more than 65% carbon. Chemical composition is greatly dependent on feedstock and pyrolysis conditions. |
| Cation exchange capacity | Low temperature biochars usually have high CEC as they are rich in oxygenated functional categorizes, indicative of high complex formation intensity with metal cations. |
| Structure | Among elements, C, O, H, and N are the most common elements and usually contribute to the main structures of biochar. |
| pH | Different alkaline salts, alkali metals (Na, K, Mg, and Ca), and CaCO3 are connected with higher pH of the biochars. Generally, biochar pH is found to be >7. |
| Surface area | The surface area of biochar boosts with the improvement in pyrolysis temperature. Highly porous structure, large surface area, and high pore volume are assumed favorable. |
| Non-organic content | The ash constituent is the nonorganic fraction of biochar include elements such as Mg, O, Ca, S, N, K, etc. |
Table 2.
The most important advantages of biochar application.
| Characteristics | Reference |
|---|---|
| Enhance the soil's properties | Oliveira et al., 2017 Tisserant, Cherubini, 2019 |
| Improvement in fertility status by increasing nutrient availability | Karimi et al., 2020 |
| Soil remediation | Wang, Wang, 2019 |
| Induces microbial activity in the soil | Hale et al., 2015 |
| Agronomic importance (crop improvement) | Saudy et al., 2021, 2022 |
| Climate change mitigation | Wang et al., 2022a; Shahrajabian, Sun 2023a,b |
| Carbon sequestration | Montanarella, Lugato, 2013 |
| Mitigate greenhouse gas emissions | Wang et al., 2023b, Li et al., 2023a |
Table 3.
The impacts of different kinds of biochar on growth and final yield of crops.
| Plant | Treatment | Key points | Reference |
|---|---|---|---|
| 1 | 2 | 3 | 4 |
| Basil (Ocimum basilicum L.) | Biochar (BC) and Chemical fertilizer |
| Pandy et al., 2016 |
| Biochar derived from black cherry wood (1, 2, and 3%) |
| Jabborova et al., 2021 | |
| Cauliflower (Brassica oleracea L.) | Nitrogen compounds (nitrate, ammonium) from biochar-amended soil in comparison to untreated (Control) |
| Losacco et al., 2022 |
| Chicory (Cichorium intybus L.) | Century-old biochar |
| Dehkordi et al., 2020 |
| Chinese cabbage (Brassica rapa) | The biochar was prepared by charring rice hull from Purnnature (Suncheon, Korea) and Yoogi Lnd (Gonchang, Korea) |
| Chun et al., 2022 |
| Chinese ginseng (Panax notoginseng) | Biochar from tobacco stems at the rates of 9.0, 12, 15, and 18 t ha−1 |
| Zhao et al., 2022 |
| Cotton (Gossypium hirsutum L.) | Biochar application rate (BCAR) at 10 t ha−1 |
| Li et al., 2023c |
| Biochar application rate (BCAR) at 4.0 t ha−1 |
| Karthik et al., 2019 | |
| Millet (Panicum miliaceum L.) | Sunflower stem biochar (15 t ha−1 biochar) |
| Taheri et al., 2022 |
| Mint (Mentha crispa L.) | The application rate of biochar and modified biochars with H2O2, KOH, and H3PO4 was 25 g kg−1 soil |
| Ghassemi-Golezani, Farhangi-Abriz, 2023 |
| Radish (Raphanus sativus L.) | Microbial biochar formulations (BCMs) and Bacillus subtilis SL-44 |
| Chen et al., 2023 |
| Red onion (Allium cepa L.) | Different biochar (BC) ratios (2% and 5% w/w) |
| Peiris et al., 2022 |
| Onion (Allium cepa L.) | Three pyrolyzed biochars cotton sticks, wheat straw and poultry litter |
| Arif et al., 2021 |
| Rice (Oryza sativa L.) | Biochar manures were applied at a rate of 12 Mg ha−1 (dry weight) in a rice paddy |
| Canatoy et al., 2022 |
| Combining 20 t ha−1 of biochar with 25% inorganic fertilizer application rate |
| Danso et al., 2023 | |
| Fe-modified and P-rich biochars |
| Yang et al., 2023 | |
| P-rich biochar |
| Yang et al., 2023 | |
| Fresh and aged holm oak biochar (BH) |
| Lopez-Pineiro et al., 2022 | |
| Biochar addition rate at 20 t ha−1 |
| Qin et al., 2016 | |
| Soybean (Glycine max L.) | The application of 2% peanut straw biochar (PSB) in polluted soil |
| Kamran et al., 2022 |
| Sunflower (Helianthus annuus L.) | The optimum biochar concentration at both CO2 levels (420 ppm and 740 ppm) was found to be 15% |
| Wang et al., 2023c |
| Four biochars namely, B1) fast pyrolysis from pine wood, B2) paper-sludge, B3) sewage sludge, B4) derived from grapevine wood. |
| Paneque et al., 2016 | |
| Wheat (Triticum aestivum L.) | 2% (w/w) bamboo biochar (BB), coconut shell biochar (CB), and maize straw biochar (MSB) |
| Wang et al., 2023a |
| 10 t ha−1 and 20 t ha−1 biochar |
| Li et al. 2023b | |
| Wheat (Triticum aestivum L.) |
| Qiu et al., 2022 | |
| Abburuzzini et al., 2019 |