Evaluation of biochars derived from food waste for synthesis gas production via pyrolysis and CO2 gasification

In this paper, a potential carbon negative energy generation process is outlined, whereby bio-waste undergoes pyrolysis and reverse Boudouard gasification to produce synthesis gas for electricity production with a solid oxide fuel cell. Constituent pieces of this process are examined through lab scale, thermogravimetric analysis of its component reactions. Five feedstocks were tested: walnut shell, pumpkin seed shell, coconut shell, pistachio shell, and corncob. It is determined that variability in gasification reactivity across biochar feedstocks correlates with differences in inorganic content that catalyzes the reverse Boudouard reaction, as well as with pyrolysis heating rate that affects biochar morphology. Kinetic studies were performed to adapt a solid-gas kinetic model for the prediction of gasification behavior of different biochar feedstocks and representation of the gasification reaction at larger scale. A modified random pore model was best suited for this application and further demonstrated the importance of inorganic content in determining the progression of reverse Boudouard gasification. •Thermogravimetric analysis was used to study reverse Boudouard reaction (CO2 gasification) of biochar feedstocks for synthesis gas production.•The effects of pyrolysis conditions on biochar gasification were analyzed.•The strongest indicator of gasification reactivity was the inorganic content of biochar, highlighting its catalytic effects.•Solid-gas model were used to calculate kinetic parameters and further established the role of inorganics in gasification reactivity.