Synergistic effects on biofuel yields and heating value during co-pyrolysis of sewage sludge and sugarcane residue under different blend ratios

In this work, fixed-bed reactor pyrolysis experiments were used to quantify the synergistic effect of sewage sludge (SS) and sugarcane residue (SR). The pyrolysis performance was examined using the synergistic index, and co-pyrolysis performance was greatly enhanced by the addition of SR. To examine the yield and quality of the products, the co-pyrolysis experiments were conducted by adding 10%, 20%, 30%, 40%, and 50% SR with SS. Additionally, the yield and quality of the final biofuel product were examined using different analytical methods. The oil yield increased with increasing temperature, and a further temperature increase decreased the oil yield. The production of biochar declined as the temperature increased, reaching its lower yield at elevated temperatures. During co-pyrolysis experiments, the yield of pyrolysis oil exhibited an increasing-decreasing pattern with the addition of SR to SS, with the highest yield observed at 30% SR addition. The co-pyrolysis experiment with 10% SR addition at a constant temperature of 500 °C indicated a maximum char yield of 32 wt% with maximum synergy, whereas the yield of gas was 33.3 wt% with 30% SR addition. SR addition enhanced the heating value of the biofuel and contributed to the formation of more alkanes, and it decreased the formation of phenolic compounds in the oil. Furthermore, the interaction between SS and SR was affected by their primary constituents. The heating value of the oil and char increased most noticeably with maximum synergy at 30% addition of SR. However, the gas generated only at the addition of 40% and 50% SR showed a beneficial synergy on the gas heating value.