**Appendix A**


**Table A1.** Experimental design (temperature, holding time, and pH) as well as reaction time and measured pH.

**Figure A1.** Regression model contour plots showing the dependence of carbon content (%daf) on reaction temperature and (**a**) holding time and (**b**) reaction time.

**Figure A2.** Regression model contour plots showing the dependence of the higher heating value (MJ kgTS<sup>−</sup>1) on reaction temperature and initial pH based on a model referring to (**a**) holding time and (**b**) reaction time (contours shown at the respective time at the corresponding center point).

**Figure A3.** Regression model contour plots showing the dependence of the process water pH (-) on initial pH and (**a**) holding time and (**b**) reaction time.
