Agri-waste valorization: pathways to sustainable bioenergy and biochemical innovation

Abstract

This systematic review examines the potential of agri-waste valorization as a sustainable solution for bioenergy and biochemical production, addressing global energy demands and waste management challenges. Agri-waste, including crop residues, livestock manure, and agro-industrial byproducts, represents a critical yet underutilized resource, with over 5 billion metric tons generated annually. Current disposal practices, such as open-field burning, contribute to environmental degradation, underscoring the urgency of circular bioeconomy strategies. The review evaluates 20 peer-reviewed studies (2015–2025), highlighting thermochemical (pyrolysis, gasification) and biochemical (anaerobic digestion, dark fermentation) technologies for converting heterogeneous feedstocks into biofuels, biogas, and high-value biochemicals. Key findings reveal significant regional disparities: developing nations prioritize decentralized systems for rural energy access, while industrialized regions focus on large-scale biorefineries. Environmental benefits include greenhouse gas (GHG) emission reductions of up to 90% per kWh output when displacing specific fossil fuels (coal), though scalability is hindered by feedstock variability, high pretreatment costs, and policy gaps. Economic viability remains contentious, with profitability dependent on subsidies and market incentives. The review advocates for integrated approaches including combining machine learning-optimized processes, circular design principles, and participatory policy frameworks, to harmonize technological innovation, ecological resilience, and socio-economic equity. By redefining agri-waste as a foundation of sustainable resource systems, this work aligns with sustainable development goals, offering a roadmap for transitioning to climate-resilient, resource-efficient economies.