Thermogravimetric analysis (TGA) was applied to evaluate the combustion behaviour of combining three feedstocks coal, biomass and polyethylene as a tri-fuel for various blend ratios. The feed materials assessed were bituminous coal (BC), anthracite coal (AC), camphor wood (CW), wheat straw (WS) and polyethylene-terephthalate (PET). The kinetic parameters of the tri-fuel blends were assessed using a Coats-Redfern integral method. The kinetic analysis indicates that the tri-fuel combustion mechanisms follow the diffusion model (D1 & D4) and can be separated in to three distinct stages. TGA analysis demonstrated that an increase in the blend ratio of biomass (CW/WS) and plastic (PET) enhances the combustion properties with respect to lowering the ignition (Ti) and burnout (Th) temperatures, along with an increase in the combustion stability indices (Cs/Csi). This enhancement of the combustion behaviour is more evident for the lower volatile anthracite coal tri-fuel blends. As the blend ratio of the anthracite coal is lowered the overall hydrocarbon-volatile content is increased as a function of increasing the biomass and plastic blend ratios. Laboratory scale analytical analysis of blending biomass, plastic with either bituminous coal or anthracite coal demonstrates a synergistic influence which is observed to benefit the overall combustion behaviour (enhanced mass loss rate and burnout). However, further investigation of tri-fuel blending streams assessing the combustion performance (Ti, Th, Ci, Csi, Ea, flue gas emissions and ash chemistry) is required at pilot and plant scale.