Abstract: The electromagnetic wave absorption of silicon carbide nanowires is improved by their uniform and diverse cross-structures. This study introduces a sustainable and high value-added method for synthesizing silicon carbide nanowires using lignite and waste silicon powder as raw materials through carbothermal reduction. The staggered structure of nanowires promotes the creation of interfacial polarization, impedance matching, and multiple loss mechanisms, leading to enhanced electromagnetic absorption performance. The silicon carbide nanowires demonstrate outstanding electromagnetic absorption capabilities with the minimum reflection loss of –48.09 dB at 10.08 GHz and an effective absorption bandwidth (the reflection loss less than –10 dB) ranging from 8.54 to 16.68 GHz with a thickness of 2.17 mm. This research presents an innovative approach for utilizing solid waste in an environmentally friendly manner to produce broadband silicon carbide composite absorbers.