Polystyrene foam (PSF), which is widely used in oyster farming in Taiwan, generates approximately 120,000-200,000 pieces of floating waste annually. The issues related to processing this waste, however, include the financial cost, incinerator clogs, human exposure to carcinogenic and non-biodegradable components, and potential debris, which threatens the seashore. In this study, we obtained methane (CH 4) and hydrogen (H 2), two crucial gases in power generation, by treating PSF waste with an atmospheric-pressure microwave plasma reactor. Substituting argon with nitrogen as the carrier gas and increasing the microwave power (1200 W) produced a higher concentration of H 2 (4739 ppm) but a lower one of CH 4 (less than 300 ppm). Treating a larger quantity of waste (0.2 g) resulted in CH 4 and H 2 levels of 19,657 ppm and 440 ppm, respectively. SEM-EDX and XRD testing confirmed the transformation of the PSF structure and a reduction in carbon (C) content in the final residue. This research demonstrates how solid waste can be recycled into valuable gases by applying plasma technology.