Post-harvest tomato plants were used to manufacture fireboards by thermopressing. Four plant materials were investigated: exhausted tomato plants ground to 5-10 mm (PHTr), tomato (PHT) and maize (PHM) plants ground to <0.5 mm, composted tomato plants (CPHT). These materials had significantly different chemical composition, which significantly influenced the fireboards mechanical properties. The PHM fireboards containing the highest amount hemicellulose and water soluble sugars, and the lowest minerals‘ amount, performed best. The data allow estimating the role of each plant proximate in determining board mechanical behavior. Moreover, the findings of the work prospect a desirable integration of municipal and agriculture biowastes as a step forward toward the valorization of renewable organic matter and the realization of the zero waste objective.