Sustainable Energy from Biomass Waste: Evaluating the Feasibility of Sawdust, Sewage Sludge, and Water Hyacinth in Mixed-Pellet Production

Abstract The increasing generation of industrial and biomass waste presents both challenges and opportunities for sustainable energy production. This study investigates the development of biomass-based energy pellets from underutilized mixed sawdust combined with non-woody biomass materials, specifically sewage sludge from wastewater treatment and Water Hyacinth (Eichhornia crassipes) in the Moratuwa area of Sri Lanka. The primary objective is to assess the feasibility of producing quality pellets from these waste streams, addressing the problem of waste management and environmental pollution while exploring potential renewable energy options. The pelletization process involved varying the proportions of non-woody biomass materials, ranging from 10% to 50%, mixed with unsorted sawdust. Comprehensive evaluations of the physical, mechanical, energy, and chemical properties of each formulation were conducted following internationally recognized testing standards, including ISO 17225-6. Statistical analyses indicated that increasing proportions of non-woody biomass materials adversely affected pellet quality, with formulations containing 10–30% Water Hyacinth (WH) and 10–20% Sewage Sludge (SS) demonstrating higher net calorific values over 14.5 MJ/kg, bulk densities over 650 kg/m 3 , ash content lower than 10%, mechanical durability over 96% showing compliance with the international industrial pellet standard of ISO 17225-6. Given the proximity of these raw materials in the Moratuwa region of Sri Lanka, which hosts a significant number of woodworking industries, this study suggests the potential for establishing small-scale, community-driven pellet production as a means to valorize waste streams. While full-scale manufacturing may require further validation, this research highlights the possibility of developing a sustainable waste utilization pathway that supports environmental management and explores renewable energy applications. Future research should focus on optimizing processing conditions and scaling up to assess economic viability and long-term sustainability.