Microwave plasma conversion of food waste using carbon foam: Production of heteroatom-doped graphene and combustible gas

The mass production of food waste (FW) has a terrible impact on the environment, but with proper treatment, FW can be transformed into a new resource. Currently, thermal conversion (especially incineration) has been the most common and efficient means of handling FW, but it also entails negative impacts, such as high carbon emissions and lower added value. In this study, a new high-efficiency thermal conversion process is proposed that uses carbon foams to induce the formation of microwave plasma (MP), which generates very high final temperatures to enable the direct conversion of FW into combustible gases and high-value-added heteroatom-doped microwave plasma graphene (HMPG) in 5–20 s. This work investigated the optimal carbonization temperature of the melamine sponge (carbon foam precursor) and the effect of microwave plasma reaction duration on the distribution of the gas products and the properties of HMPG, and HMPG was characterized in detail by Raman spectroscopy, X-ray diffraction, scanning electron microscope, etc. Ultimately, HMPG was tested in potassium ion battery anodes for evaluation of its energy storage potential, and the results showed that the capacities were able to reach ∼270 mAh g⁻¹ at 50 mA g⁻¹ after 60 cycles.