This paper presents a new composite material, which is developed by mixing calcium alginate spheres with commercially available epoxies Stycas 2850 FT (s2850) and Stycast W19 (W19). The resulting composite material is examined in terms of transmission and re°ection coe±cients in microwave frequencies (26 to 40 GHz, 70 to 110 GHz and 300 to 320 GHz). The study reveals that the new material exhibits re°ection coe±cients much lower than some commercial CR absorbers from the Eccosorb group. The experimental results justify the use of the new composite material as absorber at microwave frequencies.