Co-pyrolysis and Catalytic Pyrolysis of Biomass Using Biochar and MgFe2O4-modified Biochar in a Pilot-scale Auger Reactor

This study investigates biomass pyrolysis (PYR) and catalytic pyrolysis (CAT), and co-pyrolysis (COP) with 5 wt.% LDPE waste in a pilot-scale Auger reactor equipped with an ex-situ catalytic bed. A bifunctional catalyst based on steam-activated biochar and magnesium ferrite (SAB/MgFe2O4) was synthesized for the upgrading of pyrolysis vapors (PV). The catalyst retained a high BET surface area (768 m² g.¹) and preserved its microporous structure after MgFe2O4 impregnation, as confirmed by BET/BJH, Raman, and SEM/EDS characterization. During the initial operating period, CAT increased permanent gas (PG) production from 0.16 to 0.21 kg kg.¹ biomass (db) and reduced bio-oil yield from 0.61 to 0.57 kg kg.¹ biomass (db), reflecting enhanced cracking of pyrolysis vapors. CAT also reduced the organic concentration of the bio-oil aqueous fraction from approximately 30 to 16 wt.% and raised H2 concentration in the PG from 6.2 to 11.6 vol.% (dry gas), consistent with cracking, reforming, and possibly water-gas shift reactions. In COP, the presence of LDPE promoted higher conversion of carbon and hydrogen to the vapor phase, increased light hydrocarbon yields, and generated a wax-rich supernatant fraction in the condensed oil. Elemental mass balances revealed partial deoxygenation during CAT, with oxygen redistributed from condensable organics toward the aqueous fraction and the permanent gases. These results demonstrate at pilot-scale the suitability of SAB/MgFe2O4 catalyst for vapor upgrading and highlight co-pyrolysis with plastic waste as a promising approach worth further investigation for hydrogen enrichment in thermochemical conversion products.