Combustion Performance and Emission Characteristics of Sawdust-Coal Pellets Using Waste Styrofoam as Binder

Abstract

Managing municipal solid waste remains a major environmental challenge, particularly due to persistent non-biodegradable materials, such as expanded polystyrene (Styrofoam), and underutilised biomass, such as sawdust. While Styrofoam contributes to environmental pollution, sawdust offers significant but largely untapped energy potential. This study investigates the role of Styrofoam in sawdust–coal pellets as an energy-dense binder that causes a dilution or concentration effect depending on the baseline biomass-coal mixing matrix, aiming to enhance fuel quality while assessing associated emission trade-offs. Six pellet formulations were developed, including sawdust–coal blends (10:90 and 20:80) and pure coal controls, prepared with and without a 30 wt% Styrofoam binder. Pellets were fabricated using a manual screw press, sun-dried, and characterised via bomb calorimetry, proximate analysis, and X-ray fluorescence. Stoichiometric combustion modelling and Python-based simulations were applied to estimate flue gas compositions. Results indicate that the addition of Styrofoam increased the calorific value by 8.3–20.2% (up to 22.72 MJ/kg), reduced the moisture content to 0.95%, and increased the carbon and volatile matter contents. Although sulphur content rose slightly (0.67–1.11%), SO₂ emissions remained low and within acceptable limits. Overall, Styrofoam-enhanced pellets demonstrated improved energy performance with manageable emissions, supporting their potential for sustainable waste-to-energy applications.