Valorization of millet agro-residues for bioenergy production through pyrolysis: Recent inroads, technological bottlenecks, possible remedies, and future directions

Millets are receiving increasing attention, lately, in view of their preeminent agronomic traits, nutritional significance, and renewed emphasis on highlighting their health benefits through national and international programs. As a consequence, a variety of millets are being cultivated in different parts of the world resulting in significant amount of millet agro-residues. Present study comprehends critical analysis of reported investigations on pyrolysis of different millet agro-residues encompassing (i) physico-chemical characterization (ii) kinetics and thermodynamic parameters (iii) reactors employed and (iv) relationship between the reaction conditions and characteristics of millets-derived biochar and its prospective applications. Based on the analysis of reported investigations, specific research gaps have been figured out. Finally, future directions for leveraging the energy potential of millet agro-residues are also discussed. The analysis elucidated is expected to be useful for the researchers for making further inroads pertaining to sustainable utilization of millet agro-residues in tandem with other commonly employed agro-residues.

Automated summary

Recently, millets have gained increasing attention due to their outstanding agronomic traits, nutritional significance, and focus on promoting their health benefits. This has resulted in cultivation of various millet varieties worldwide, generating a significant amount of millet agro-residues. This study critically analyzes previous investigations on the pyrolysis of different millet agro-residues, including physico-chemical characterization, kinetics and thermodynamic parameters, reactors used, and the relationship between reaction conditions and characteristics of millet-derived biochar and potential applications. Specific research gaps are identified based on the analysis, and future directions for harnessing the energy potential of millet agro-residues are discussed. This analysis is expected to be useful for researchers in further exploring the sustainable utilization of millet agro-residues in conjunction with other commonly used agro-residues.