<![CDATA[The conversion of biomass waste into biochar and densified solid fuels has become increasingly important because it links residue management, fossil fuel substitution, and industrial decarbonization. This review examines 57 unique publications from 2020–2026 identified through two bibliographic extractions and prioritizes 49 studies that remained relevant after deduplication and thematic screening. The analysis is organized according to the value chain: feedstock characteristics; pyrolysis and torrefaction; densification and binder selection; combustion and cofiring; biological–thermochemical process integration; and non-energy applications. The synthesis shows that conversion temperature is the primary parameter controlling biochar yield, fixed-carbon content, calorific value, porosity, thermal stability, and reactivity. Densification improves bulk density, mechanical strength, storage, and feeding performance. However, binder type and dosage create trade-offs among calorific value, ash content, emissions, water resistance, and cost. Recent evidence has expanded the role of biochar beyond household fuel to include power-plant cofiring, blast-furnace injection, use as a reducing agent and foaming material in the DRI–EAF route, graphitized carbon materials, and distributed pyrolysis systems incorporating bio-tar and heat recovery. Nevertheless, climate benefits are not automatically achieved because they depend on biomass sources, process energy requirements, avoided open burning, particulate emissions, PAHs, NOx, heavy-metal transfer, and end-use choices. This review proposes a decision-making framework based on feedstock–process–product compatibility, performance normalization per unit of energy, quality verification against applicable standards, and multiobjective optimization. Priority research areas include machine-learning-based predictive models, low-ash binders, dust-safety management, long-term industrial validation, and techno-economic and life-cycle assessments comparing energy, material, and carbon-sequestration pathways. Biochar should therefore be regarded not as a single product but as a circular carbon platform that must be designed according to the local application context.]]>
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