Optimization of Switchgrass Combustion for Simultaneous Production of Energy and Pozzolan

Combustion of switchgrass, a low-carbon fuel, generates energy and ash that can be recycled as a pozzolan in cement. This study aimed to optimize switchgrass combustion to achieve high-energy conversion and ash recycling value for cement. Combustion factors under investigation included temperature (350°C, 450°C, 550°C, or 650°C) and retention time (1 h or 4 h). Energy release was quantified by thermogravimetric analysis-differential scanning calorimetry, and ash pozzolanic activity was assessed with the concrete strength test. A numeric simulation model of the pozzolanic reaction, based on unbiased experimental data from Ca(OH)2-ash suspensions, provided insight into how combustion conditions affected the pozzolanic properties of switchgrass ash. Consequently, combustion at 550°C for 4 h was recommended for concurrently optimizing the ash pozzolanic activity (114%) and energy output (4.21 kJ/g) from switchgrass.