Production and Characterization of the Bio-Oil Obtained by the Fast Pyrolysis of Spent Coffee Grounds of the Soluble Coffee Industry

Agro-industrial wastes are abundant and low-cost sources of energy and chemicals. Biomass account for 14% of the world’s energy production. Industrial residues of production of soluble coffee (spent coffee grounds - SCG) have great potential due to its large-scale production and can be transformed by pyrolysis, in liquid, solid and gaseous products with applications from energy to chemicals. This work has the objective of producing bio-oil from the pyrolysis of industrial SCG, characterize it by chromatography and indicate its possible applications. As SGC contains a large amount of glycerides, they were extracted from SGC before the pyrolysis, aiming to obtain a better bio-oil from the residue. The yield in vegetable oil was 5.2% and its analyses showed that 50% are saturated acids (mainly palmitic 27.6%) and other 50% are unsaturated ones (mainly linoleic acid 35.3%). This composition qualifies this oil for biodiesel purposes. The residue (SGC after extraction) was submitted to pyrolysis, yielding 30% in liquid products, being 6% bio-oil. The bio-oil was analyzed by gas chromatography being identified free fatty acids, hydrocarbons, phenols and N-compounds. The heteroatomic compounds limit the use as biofuel but can be interesting for the pharmaceutical, agrochemical and fine chemicals industries.农林工业废弃物储量丰富，是成本低廉的能源与化学品原料来源。生物质占全球能源总产量的14%。可溶性咖啡生产产生的工业残渣——废咖啡渣（spent coffee grounds，SCG）因规模化产出而具备巨大应用潜力，可通过热解工艺转化为液态、固态和气态产物，应用覆盖能源至化学品制备等多个领域。本研究旨在以工业级废咖啡渣为原料，通过热解制备生物油，采用色谱法对其进行表征，并明确其潜在应用方向。由于废咖啡渣含有大量甘油酯，本研究在热解前先从中提取甘油酯，以期从该残渣中获得品质更优的生物油。所得植物油产率为5.2%，成分分析显示其中50%为饱和脂肪酸（主要成分为棕榈酸，占比27.6%），剩余50%为不饱和脂肪酸（主要成分为亚油酸，占比35.3%）。该成分组成使该植物油具备用于制备生物柴油的可行性。提取后的残渣（脱除甘油酯的废咖啡渣）被用于热解实验，液态产物产率达30%，其中生物油占比6%。通过气相色谱对所得生物油进行分析，共鉴定出游离脂肪酸、烃类、酚类及含氮化合物等组分。尽管含杂原子化合物限制了其作为生物燃料的应用，但该生物油在制药、农用化学品及精细化工行业中具备潜在应用价值。