Carbon Dioxide Methanation Enabled by Biochar-Nanocatalyst Composite Materials: A Mini-Review

Due to ever-increasing global warming, the scientific community is concerned with finding immediate solutions to reduce or utilize carbon dioxide (CO2) and convert it in useful compounds. In this context, the reductive process of CO2 methanation has been well-investigated and found to be attractive due to its simplicity. However, it requires the development of highly active catalysts. In this mini-review, the focus is on biochar-immobilized nanocatalysts for CO2 methanation. We summarize the recent literature on the topic, reporting strategies for designing biochar with immobilized nanocatalysts and their performance in CO2 methanation. We review the thermochemical transformation of biomass into biochar and its decoration with CO2 methanation catalysts. We also tackle direct methods of obtaining biochar nanocatalysts, in one pot, from nanocatalyst precursor-impregnated biomass. We review the effect of the initial biomass nature, as well as the conditions that permit tuning the performances of the composite catalysts. Finally, we discuss the CO2 methanation performance and how it could be improved, keeping in mind low operation costs and sustainability.