(513a) The Catalytic Effect of Ash Content on CO2 gasification of Biochar

Carbon negative energy is an essential solution to limit global temperature rise to within 2 degrees Celsius above pre-industrial levels. An alternative Bioenergy with Carbon Capture and Storage (BECCS) process that involves converting biowastes to synthesis gas has been proposed as a theoretically carbon negative method to produce electricity. This research focuses on the reactivity of different biochar feedstocks to CO₂ gasification to produce synthesis gas (the reverse Boudouard reaction). While pyrolysis decomposes organic material in biomass, inorganic materials remain in the ash of the char. The effect of the inorganics on CO₂ gasification reactivity was investigated for biochar from four feedstocks: pistachio shell, walnut shell, corncob, and pumpkin seed shell. Feedstocks were acid-washed to effectively remove inorganic ash and the reactivity of these were compared to their respective unleached feedstock. Reactivities were compared through isothermal thermogravimetric analysis (TGA) tests at 900°C. For most samples, acid-washing had a significant effect on reaction rate, indicating that biochar ash catalyzes the reverse Boudouard reaction.