Faculty of Science and Technology, Technical Physics Group/Bioenergy and Biofuels Laboratory, Free University of Bozen-Bolzano, Piazza Università 5, IT-39100, Bolzano, Italy.
School of Chemical Engineering, Unit of Environmental Science and Technology, National Technical University of Athens, 9 Iroon Polytechniou Str, GR-15780, Athens, Greece.
Environ Sci Pollut Res Int. 2019 Dec;26(35):35473-35481. doi: 10.1007/s11356-019-04919-3. Epub 2019 May 7.
Spent coffee grounds are the moist solid residues of coffee brewing and in most cases, the disposal is done without any intermediate valorization actions for materials and energy recovery. State-of-the-art applications include extraction of the liquids and application of high-temperature pyrolysis. Both strategies have significant potential but have also some disadvantages (extensive pre-treatment, high costs) when applied on a large scale. This study highlights the lack of mild pyrolysis valorization strategies and presents the idea of the "COFFEE BIN." Separated spent coffee grounds are collected, dried, and thermally treated. The optimal pyrolysis conditions were identified and product characteristics and the mass balances were assessed. Elemental analysis, thermogravimetric analysis, physisorption analysis and higher heating value (HHV) determination was performed for the characterization of the carbonaceous products. The torrefied coffee grounds returned solid yields from 78 to 83%, which are significantly higher than in other cases of conventional biomass and heating values of 24-25 MJ/kg. Higher temperature pyrolysis did not sustain the advantage of increased returned mass yields and the adsorbance potential of all the carbonaceous products was lower than 25 cm/g. The study highlighted that spent coffee grounds-due to the nature of their production process via roasting-can be suitable for torrefaction because of the high recovered solid yield and the high energy density. The results will be used for the development of a collection scheme for spent coffee grounds in a big municipality of Athens (Greece).
用过的咖啡渣是咖啡冲泡后的湿润固体残渣，在大多数情况下，这些残渣在没有任何中间材料和能源回收增值措施的情况下就被处理掉了。最先进的应用包括提取液体和应用高温热解。这两种策略都有很大的潜力，但在大规模应用时也有一些缺点（需要广泛的预处理，成本高）。本研究强调了缺乏温和热解增值策略，并提出了“咖啡渣桶”的概念。分离出的用过的咖啡渣被收集、干燥并进行热处理。确定了最佳的热解条件，并评估了产品特性和质量平衡。对炭质产品进行了元素分析、热重分析、物理吸附分析和高位发热量（HHV）测定，以对其进行表征。烘焙后的咖啡渣的固体收率从 78%到 83%不等，明显高于其他常规生物质的情况，其发热值为 24-25MJ/kg。较高的温度热解并不能保持增加的返回质量收率的优势，所有炭质产品的吸附能力都低于 25cm/g。研究结果表明，由于咖啡渣是通过烘焙生产的，其性质特殊，因此可以适合进行烘焙，因为其固体回收率高，能量密度高。研究结果将用于开发希腊雅典一个大城市的用过的咖啡渣收集方案。
