Biomass-derived pyrogenic carbon(biochar)is a carbon-rich material produced by thermochemical treatment of lignocellulosic biomass in the absence of oxygen(or oxygen-limited conditions).Due to its highly stable structure and persistence in nature,biochar is believed to be chemically and biologically inert having the potential to mitigate global warming by long-term C-sequestration and can stay in soil for several centuries-millennia.Additional advantages of biochar include improved soil productivity/fertility,environmental remediation,wastewater treatment and solid fuel for energy production.Inventiveness in biochar science for its agro-environmental and climate benefits is fast emerging among researchers,who are swiftly accelerating studies to explore its potential.Although biochar-based science is progressing rapidly,many areas of uncertainty need to be addressed.In the present study,we conducted series of experiment including production and modification of biochars,characterizations using an array of techniques(SEM,TEM,HRTEM/SAED,TEM-EDS,FTIR,TGA,XRD,Brunauer-Emmett and Teller(BET),stable isotope measurement,Elemental Analyzer and ICP-MS)and their environmental applications:i.e.,(1)co-firing of pyrolyzed biomass feedstocks with coal for clean energy and emission-reduction of potentially toxic elements(PTEs);(2)efficient removal of metal ions from aqueous medium using biochar-coated RBC-Ti02@C nanocomposite;(3)addition of biochar as soil amendment to minimize the health risks of PTEs;(4)priming effects of biochar on native soil organic carbon and its potential for carbon sequestration.A total of 168 biochar samples were prepared under various operating conditions(temperature:300-700 ℃,retention time:15-90 min,heating rate:1-10℃ min-1,gas flow rate:20-200 sccm(ml min-1)and particle size:<200-10 mesh)using eight(8)biomass feedstocks.Results revealed that temperature,gas flow rate and particle size have significant control on product yield and physico-chemical characteristics of biochars compared to the other operational conditions.In addition,temperature,retention time and heating rate remarkably influenced stabilization of PTEs in biochar.No potential ecological risk was observed during pyrolysis process,the RI values for single elements demonstrated low risk at all operating conditions and its value significantly decrease with increasing the values of operating conditions.The isotopic measurements revealed that all operating conditions do not significantly change the total(δ13Ctotal)and organically bound(δ13Corg)C isotope values from the original biomasses;however these significantly influenced carbonate bound C and O isotope values(δ13Ccarbonatc and δ18Ocarbonatc).The characterization and laboratory experimentations indicate that biochar synthesized under higher pyrolysis temperature,extended retention time and,lower heating and gas flow rates with fine particle size has utility as a potential C-sequestration and remedial agent to mitigate global climate change and adsorption of environmental polluants,respectively.In additions,modified biochar(biochar coated RBC-TiO2@C nanocomposite)has strong ability to adsorbed environmental pollutants from aqueous medium.Furthermore,our results show that biochar as a renewable solid bio-fuel source due to higher calorific values,is a suitable option for their use in existing coal-fired energy generation system to achieve the environmental friendly clean energy and reduction of gaseous PTEs emission.