Co-hydrothermal carbonization of different feedstocks to hydrochar as potential energy for the future world: A review

Co-hydrothermal carbonization (co-HTC) has emerged recently as a promising thermochemical technique that can transfer organic solid residue (e.g., biomass, sewage sludge, plastic, livestock manure) into value-added products (i.e., hydrochar). This advanced mechanism conceals the weakness of hydrochars derived from the hydrothermal carbonization (HTC) of a single feedstock. The co-HTC of various feedstock blends used for hydrochar is reviewed in this article. Biomass/sludge, biomass/plastic, biomass/coal, biomass/manure were the most common feedstock blends. Many studies have found that co-HTC, compared to single feedstock, enhances the yield, ultimate and proximate properties, higher heating value (HHV), thermal behaviors, and overall quality of hydrochars. The synergistic effects of feedstock types, blending ratio, temperature, and residence time are also discussed. The feedstock mixing ratio emerges as…