Synergistic improvements in energy recovery and bio-oil quality through integrated thermochemical valorization of agro-industrial waste of varying moisture content

• Published in: Bioresource technology 2024-02, Vol.394, p.130173-130173, Article 130173
• Main Authors: Karod, Madeline, Rubin, Samantha F., Goldfarb, Jillian L.
• Format: Article
• Language: English
• Subjects: Biochar; Biomass; Hydrothermal carbonization; Integrated biorefinery; Pyrolysis; Synergy
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2023.130173

[Display omitted] •Wet and dry wastes mixed in cascading thermochemical valorization pathways.•Hydrothermal carbonization (HTC) as pyrolysis pretreatment enhances biochar HHV.•HTC as pretreatment decreases biochar volatile matter beyond additive prediction.•Mixing dry waste with hydrochar lowers acidity and O/C of pyrolysis bio-oil. Two thermochemical valorization schemes were investigated for co-upgrading dry and wet agricultural wastes through integrated hydrothermal carbonization (HTC) and pyrolysis. In the first pathway, dry and wet wastes were co-carbonized. The resulting hydrochar was pyrolyzed to yield an energy dense biochar (26–32 MJ/kg) high in fixed carbon (41–86 wt%) and low in volatile matter (6–12 wt%). The resulting bio-oil was lower in carboxylic acids and higher in phenols than predicted based on an additive scheme. In pathway two, wet waste (only) underwent HTC and the resulting hydrochar was mixed with dry waste and the mixture pyrolyzed. This pathway showed a lower biochar yield (32–67 wt%) and lower HHV values (24–31 MJ/kg) but higher fixed carbon content (65–84 wt%). The bio-oil contained more carboxylic acids than pathway 1 bio-oil. Pathway 1 biochars were more thermally reactive than pathway 2 biochars, reflecting a synergistic deoxygenation that occurs when incorporating dry waste in HTC prior to pyrolysis.