Co-liquefaction of Sewage Sludge and Rice Straw/wood Sawdust: the Effect of Process Parameters on the Yields/properties of Bio-Oil and Biochar Products

Liquefaction is a promising technology for the preparation of bio-oil and biochar products from sewage sludge (SS). Co-liquefaction of SS and agricultural/forestry biomass is likely a potential method for obtaining high yield/quality of bio-oil and biochar. In this work, rice straw (RS) and wood sawdust (WS) were selected as representatives of agricultural/forestry biomass and the effects of main process parameters during the co-liquefaction of SS-RS/WS on the yields/properties of bio-oil and biochar were explored in details. The proper reaction temperature, solid-liquid ratio and reaction time for the co liquefaction of SS-RS/WS were suggested to be 280-300 degrees C, 0.1 g/mL and 10-30 min, respectively. Potassium/sodium salt (-OH and -CO3) catalysts could efficiently enhanced the co-liquefaction of SS-RS/WS. The introduction of RS/WS into the liquefaction of SS would reduce the contents of nitrogen and sulfur in bio-oil and enhance the formation of phenolic compounds. In addition, co-liquefaction of SS-RS could promote the percentage of lower-boil-point compounds in bio-oil. Although the thermal stability, surface area and pore volume of biochars slightly decreased, the contents of organic matters in biochars were obviously improved, suggesting higher potential in land application. (C) 2019 Elsevier Ltd. All rights reserved.