tSSF performance at increasing initial solids. Experimental data and model predictions from tSSF with 20 (blue, dashed), 50 (red, dotted), and 77 (black, solid) g/L initial Avicel, with 4 FPU/g cellulose. A) Cellulose. B) Conversion. C) Ethanol. Points indicate experimental data, lines show model predictions. Data indicate that the model predicts performance at 20 and 50 g/L initial Avicel, but over predicts experimental data at 77 g/L initial Avicel. Error bars in Panel A indicate the standard error of the cellulose concentration measurement.