Thermochemical liquefaction of cattle manure using ethanol as solvent: Effects of temperature on bio-oil yields and chemical compositions

Abstract

Cattle manure was converted into bio-oil via sub- and super-critical liquefaction with ethanol as the solvent. The effects of various reaction parameters, including the reaction temperature (T, 180–300 °C), solid-liquid ratio (S1, 5–15%), and solvent filling ratios (S2, 10–30%) on the yield of bio-oil (OCM) and residue (RCM) from liquefaction of cattle manure were studied. The yield of bio-oil was positively correlated to reaction temperature suggesting higher reaction temperature could promote the fragmentation of the polymers transformed into a liquid oil-rich phase and the maximum OCM relative yield (32.14 ± 0.19%) was obtained at 300 °C. OCM had HHV of 25.63–33.41 MJ/kg and LHV of 23.85–31.39 MJ/kg, respectively, suggesting their potential for use as a renewable energy to replace fossil energy. The GC-MS analyses demonstrated that the major compounds in OCM were esters, hydrocarbons, alcohols, phenolic compounds, nitrogenous and bromine components, the compositions of OCM was similar to that of biodiesel. The presence of ester compounds in OCM which was attributed to the degradation of cellulose and hemicelluloses. Carbon-normal paraffin gram (C-NP) analysis indicated that C18 and C20 species comprised the bulk of the hydrocarbon compounds from OCM.