Sludge residues from pulp and paper mill waste streams contain cellulose and other polysaccharides that can be regenerated into sugars for biochemical production. The high ash content of sludge, ranging from 10 to 50 wt%, is a barrier to carbohydrates valorization. It is important to understand the effect of ash on the downstream processing and to develop a process to effectively remove ash. This study focuses on the enzymatic hydrolysis optimization of sludge as well as the impact of ash on the system. A majority of ash was removed by a screen and the ash content in sludge was reduced from 45% to 1.5%. After adjusting pH with hydrochloric acid, the cellulolytic enzyme was used to produce sugars. High glucose and xylose conversion (90%) were achieved with 5 FPU cellulase/g od sludge. The results show the optimum pH for cellulase activity is lower than that used for sugar production from lignocellulosic feedstocks. Also, ash composition and content significantly affect the pH during enzymatic hydrolysis. A series of experimental conditions were conducted and evaluated to elucidate the mechanisms by which ash affects the enzymatic hydrolysis of pulp and paper sludge. This work is expected to increase both the value and feasibility of recycling wet waste streams generated by the pulp and paper industry.

Effect of ash on enzymatic hydrolysis of paper sludge to produce sugars

ACS Fall 2020 Virtual Meeting

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