Biodiesel production produces significant quantities of impure crude glycerol as a by-product. Recent increases in the global biodiesel production have led to a surplus of crude glycerol, rendering it a waste. As a result, different methods for its valorisation are currently being investigated. This paper assesses the life cycle environmental impacts of an emerging technology for purification of crude glycerol – a multi-step physico-chemical treatment – in comparison to incineration with energy recovery commonly used for its disposal. For the former, three different acids (HPO, HSO and HCl) are considered for the acidification step in the purification process. The results suggest that the HSO-based treatment is the best option with 17 net-negative impacts out of the 18 categories considered; this is due to system credits for the production of purified glycerol, heat and potassium salts. In comparison to incineration with energy recovery, the HSO-based process has lower savings for the climate change impact (−311 versus −504 kg CO eq./t crude glycerol) but it performs better in ten other categories. Sensitivity analyses suggest that that the impacts of the physico-chemical treatment are highly dependent on crude glycerol composition, allocation of burdens to crude glycerol and credits for glycerol production. For example, treating crude glycerol with lower glycerol content would increase all impacts except climate change and fossil depletion due to the higher consumption of chemicals and lower production of purified glycerol. Considering crude glycerol as a useful product rather than waste and allocating to it burdens from biodiesel production would increase most impacts significantly, including climate change (22–40 %), while fossil depletion, freshwater and marine eutrophication would become net-positive. The findings of this research will be of interest to the biodiesel industry and other industrial sectors that generate crude glycerol as a by-product.

中文翻译：

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生物柴油生产中粗甘油的增值对环境的影响——生命周期的角度

生物柴油生产会产生大量不纯的粗甘油作为副产品。最近全球生物柴油产量的增加导致粗甘油过剩，使其成为浪费。因此，目前正在研究不同的评估方法。本文评估了一种新兴的粗甘油纯化技术（一种多步骤物理化学处理）的生命周期环境影响，并与通常用于处理粗甘油的焚烧和能量回收进行比较。对于前者，纯化过程中的酸化步骤考虑三种不同的酸（HPO、HSO 和 HCl）。结果表明，基于 HSO 的治疗是最佳选择，在考虑的 18 个类别中，有 17 个净负面影响；这是由于生产纯化甘油、热量和钾盐的系统积分。与能量回收焚烧相比，基于 HSO 的工艺对气候变化影响的节省较低（-311 千克二氧化碳当量/吨粗甘油与-504 千克二氧化碳当量/吨粗甘油），但在其他十个类别中表现更好。敏感性分析表明，物理化学处理的影响高度依赖于粗甘油的成分、粗甘油的负荷分配以及甘油生产的信用。例如，用较低甘油含量处理粗甘油会增加除气候变化和化石消耗之外的所有影响，因为化学品消耗增加，纯化甘油产量减少。将粗甘油视为一种有用的产品而不是废物，并将生物柴油生产的负担分配给它，将显着增加大多数影响，包括气候变化（22-40％），而化石消耗、淡水和海洋富营养化将变得净积极。这项研究的结果将引起生物柴油行业和其他产生粗甘油副产品的工业部门的兴趣。