Smart integrated biorefineries in bioeconomy: A concept toward zero-waste, emission reduction, and self-sufficient energy production

Integrated biorefineries play a transformative role in sustainable development by converting biomass and biogenic residues into high-value products while minimizing waste, emissions, and resource inefficiencies. This review explores innovations in biorefinery processes, emphasizing the synergy between thermochemical, biochemical, and biological technologies such as pyrolysis, fermentation, anaerobic digestion, hydrothermal carbonization, and algae and insect systems. Recent advancements, including hydrothermal humification and fulvification, enhance nutrient recovery, carbon sequestration, and near-zero waste production by generating artificial humic substances. Smart integrated biorefineries and the sustainable and circular bioeconomy systems are introduced as frameworks that promote synergy, interconnectivity, and resource optimization. These concepts emphasize that biomass valorization should be maximized before its final use. Biochar plays a multifaceted role beyond carbon sequestration. Rather than premature burial, it can be derived from fermented residues for lactic acid production or used to enhance fermentation and methane yields in anaerobic digestion. Additionally, nutrient-loaded biochar serves as a slow-release fertilizer, mitigating runoff, and GHG emissions. Meanwhile, heat from biochar production can generate electricity, and CO₂ emissions can support algae cultivation. Bio-oil, another byproduct, can be upgraded into platform chemicals, forming a closed-loop system that optimizes biomass utilization and minimizes environmental impact. Conventional biomass treatment methods, such as incineration, combustion, and composting, waste valuable resources and contribute to environmental degradation. Instead, a closed-loop, self-optimizing approach ensures full biomass utilization while addressing planetary boundaries. By integrating machine learning, digital twins, and decision-support systems, smart integrated biorefineries enhance resource efficiency, adapt to market demands, and accelerate the transition to a low-carbon, resource-efficient future.