Co-liquefaction of livestock manure and food waste: Synergistic effects and product combustion performance

Abstract

With the depletion of fossil energy, alternative biomass energy has been studied as a potential candidate. Our study focused on the co-liquefaction of livestock manure (cattle manure) and food waste (peanut residue), aiming to obtain high-quality bio-oil and bio-char to maximize resource utilization. By adjusting the ratios of the two types of biomass in a closed system, products distribution in the reaction were controlled to obtain biofuel with high carbon and hydrogen, low oxygen and nitrogen content. Under the optimal reaction conditions (270 °C, 30 min, peanut residue/cattle manure = 3/1), the overall yields of bio-oil (a mass fraction of 23.5%) and bio-char (a mass fraction of 18.5%) were obtained, and the higher heating value of the bio-oil reached the highest of 31.74 MJ/kg. It was found that Maillard and Mannich reactions occurred during the co-liquefaction process, and the experimental values of bio-char yield was higher than the calculated values with higher carbon and nitrogen content, indicating the synergistic effect during the formation of the bio-char. The migration and transformation of carbon and nitrogen were explored, and it was found that nitrogen in bio-oil and aqueous phase was transferred to bio-char. All experimental energy recoveries (bio-oils and bio-chars) of co-liquefaction were higher than the calculated ones, indicating that the synergistic effect between peanut residue and cattle manure promoted the energy recovery of the co-liquefaction products.