Hasnain, S.A. , Siddique, M. , Khan, G. , Abass, A. and Abubakar, A.M. 2025. Greener pretreatment and the characterization of neem and babul tree barks for lignin extraction . International Journal of Sustainable Energy and Environmental Research. 14, 2 (Dec. 2025), 90–103. DOI:https://doi.org/10.18488/13.v14i2.4555.