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.

农业工业废弃物是储量丰富且成本低廉的能源与化学品原料。生物质占全球能源总产量的14%。可溶性咖啡生产过程产生的工业残渣——废弃咖啡渣（Spent Coffee Grounds, SCG），因具备规模化产出的特点而具备极高利用潜力，可通过热解（pyrolysis）转化为液态、固态与气态产物，应用场景覆盖从能源到化学品的多个领域。本研究旨在通过工业级废弃咖啡渣的热解制备生物油，借助色谱技术对其进行表征，并明确其潜在应用方向。鉴于废弃咖啡渣富含大量甘油酯，本研究先对其开展甘油酯萃取预处理，以期从该残渣中获得品质更优的生物油。经萃取得到的植物油产率为5.2%，成分分析显示其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%）。该组分特性使其符合生物柴油的制备要求。对萃取后的残渣（即经预处理的废弃咖啡渣）开展热解实验，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潜力，但该类组分在制药、农用化学品及精细化工行业中具备可观的应用价值。