(583e) The Impact of CO2 in Pyrolysis and Ultimate Reactivity of Biochars Made from Food Wastes

Bioenergy with carbon capture and storage (BECCS) is a concept that produces bioenergy in a carbon negative manner, which can be a powerful tool to combat climate change. Instead of the traditional BECCS method (biomass-fired plants with carbon capture), we study an alternative approach that consists of reacting biochar, derived from biowaste, with carbon dioxide to produce synthetic gas with high carbon monoxide concentrations to fuel solid-oxide fuel cells (SOFC) to generate electricity. The SOFC enables easier separation of carbon dioxide for sequestration. For this research, we investigate the effects of carbon dioxide in the pyrolysis process to understand its impact on the char product and its reactivity in biochar gasification. Biowaste feedstocks used in this study include corncob, pumpkin seeds, sunflower seeds, pistachio shells, and walnut shells. Flash pyrolysis is performed at 500^oC with varying amounts of carbon dioxide in nitrogen. The effect of carbon dioxide on biochar yield differed for each feedstock, in which some samples had higher solid mass yield with carbon dioxide whereas other samples didn’t have any influence. Thermogravimetric analysis (TGA) runs were conducted to assess biochar reactivities in the reverse Boudouard reaction using temperature-programmed oxidation (TPO) tests to 900^oC, a typical operating temperature for SOFCs. The addition of carbon dioxide had limited improvements in the gasification reaction for most biowaste samples. However, for the high ash content feedstocks like corncob, carbon dioxide in pyrolysis had a negative effect on biochar reactivity in the gasification reaction.