The disposal of agro-industrial waste in a conventional waste management system results in significant greenhouse gas emissions. Although converting agricultural residues into bioproducts can reduce the environmental impact of the agricultural sector, adoption remains limited due to a lack of management solutions tailored to specific waste types, local conditions, and process parameters. The literature lacks in-depth comparative studies on the different methods for valorizing fennel waste in order to identify the most effective strategy. This study evaluates alternative management strategies for fennel waste generated on a farm in Campania, Italy, using life cycle assessment as a decision-support tool. Four scenarios were assessed per ton of fennel waste: conventional waste management, composting, aqueous extraction of compost, and pyrolysis for the production of biochar, electricity, and thermal energy. All valorization scenarios show lower CO₂-equivalent emissions than conventional waste management. However, pyrolysis exhibits higher impacts across several other environmental indicators due to energy-intensive pre-treatment. Composting provides the greatest overall environmental benefits, especially when considering the system's expansion thanks to the partial substitution of synthetic fertilizers and carbon sequestration.