Study of the efficiency of energy use of willow chips and torrefied hydrolytic lignin pelletsViktor Lyubov, Anatoly Popov, Evgeniya Popova, Sergey Tretyakov, Andrey Paramonov and Sergey KoptevE3S Web Conf., 265 (2021) 04006DOI: https://doi.org/10.1051/e3sconf/202126504006