Economic Value-Added Innovative Management of Leaf Waste in Green Areas of Government Agencies, Bangkok, Thailand

Government-managed urban green spaces in Bangkok produce large quantities of leaf waste, which are typically sent to landfills, incurring considerable costs. This study assessed a novel method for valorizing this waste by converting dried, ground leaf material into compressed planting blocks (PL) to serve as a soil substitute. Annual leaf waste data from three government agencies were used to estimate production capacity and inform economic modeling. Agronomic trials with Mitragyna speciosa (Korth.) Havil. compared PL, coconut fiber (PC), and mixed soil with fertilizer over eight weeks in controlled nursery conditions. The results indicated that PL supported plant growth with a final mean height of 20.10 ± 2.01 cm, similar to PC (20.70 ± 1.90 cm) and significantly greater than soil (14.40 ± 1.50 cm) (p < 0.001). Economic analysis showed high net present values (THB 9.16–13.76 million) and very short payback periods (less than 0.08 years). The process proved technically feasible and profitable, while also reducing waste disposal costs, minimizing landfill emissions, and providing a cost-effective, biodegradable planting medium. This method presents a scalable solution for sustainable organic waste management in tropical urban areas, supporting several Sustainable Development Goals and advancing the circular bioeconomy.