| Biochar feedstock | Biochar properties measured (elemental composition) | Hazards exhibited | References |
| Bamboo | P, EC, H, Corg, Corg/N, Atomic H/Corg, ash, CEC, SA (BET), alkalinity | Cu, Zn | [23] |
| Municipal sewage sludge | pH, volatile matter, ash, fixed carbon, N, C, H, S, O, Cu, Cr, Zn | Cu, Cr, Zn | [24] |
| Pitch pine wood char and natural char | Helium solid density, surface area, electrical resistivity, H/C ratio | 40 TCPL contaminant PAHs detected | [25] |
| Wheat straw | pH, SOC, N, bulk density | Increased CH4 and CO2 emission Decreased N2O emission | [26] |
| Rice straw | Ash, C, H, N, O, H/C, O/C | Cu, Cd, Pb, Cr, Zn, Ni | [27] |
| Green waste compost and hardwood | pH, total organic carbon, water-soluble carbon, dissolved organic carbon, water-soluble nitrogen, and concentrations of dissolved total nitrogen | Pb, Zn, As, Cu Cd, PAH reduced | [28] |
| Paper mill sludge | pH, volatile matter, ash, fixed carbon, N, C, H, S, O, Cu, Cr, Zn | Cu, Cr, Zn | [24] |
| Sawdust | Ash, C, H, N, O, H/C, O/C | Cu, Cd, Pb, Cr, Zn, Ni | [27] |
| Wheat straw | pH, SOC, N, bulk density, surface area, ash content | CH4 enhanced with more application N2O emission reduced, CO2 unchanged | [29] |
| Rice straw | P, EC, pH (H2O), C, N, H, Corg, Corg/N, Atomic H/Corg, ash, CEC, SA (BET), alkalinity | Cu, Pb and Zn | [23] |
| Wheat straw, poplar wood, and spruce wood | Ash content, C, N, H | 9 US EPA PAHs identified | [30] |
| Slaughterhouse sludge | pH, volatile matter, ash, fixed carbon, N, C, H, S, O, Cu, Cr, Zn | Cu, Cr, Zn | [24] |
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