In the present work, emphasis has been given on the utilization of waste materials to make cost-effective microwave absorbing composites. Rice husk and exhausted activated charcoal (EAC) were used as waste material, where rice husk is a form of agricultural waste and exhausted activated charcoal was extracted from an exhausted water filter cartridge. Thereafter, zinc metal powder was dispersed in different weight ratios in the mixture of rice husk and exhausted activated charcoal using a planetary ball mill. The X-ray fluorescence (XRF), X-ray diffraction (XRD), and the particle size analyses were done to analyze element composition and particle size. For dielectric properties analysis, vector network analyzer (VNA) was used. Results reveal that composites have the potential for microwave absorption in 2-18 GHz frequency range, sample RHZ 3 having 6 wt.% Zn content gives the maximum reflection loss value of -21.27 dB at 9.2 GHz for a material thickness of 13.9 mm. The experimental results were then used to design a metamaterial microwave absorber. The simulated results show the good microwave absorption characteristics. The metamaterial absorber showed an absorption bandwidth of around 4.1 GHz which ranges from frequency of 14.1 GHz to 18.2 GHz at total thickness of 1.7 mm.