Abstract：
Phosphate rock is a finite, non-renewable mineral resource that is used primarily in fertiliser production. The scarcity and the increasing demand for this finite material led the European Commission to include it in the critical raw material list in 2014. As a consequence, efforts have been directed towards enhancing material use efficiency, initiating recycling efforts, and formulating waste policies to mitigate the criticality of raw materials. Interest in the development of technologies for nutrient recovery from organic waste streams has increased in recent years, and dairy processing sludge (DPS) is a potential input waste stream. Although the recovery of P from DPS can contribute to more circular flows of nutrients in society, it has to be assessed whether there are also overall environmental gains. This paper reports on a life cycle assessment (LCA) of the environmental impacts of three scenarios for phosphorus (P) recovery involving hydrothermal carbonization (HTC) and struvite precipitation and a comparison to a reference drying scenario. HTC produces a solid fraction (hydrochar), and a liquid fraction (process water) and in one of the scenarios (Scenario 3), leaching the hydrochar for additional P recovery is considered. From the process water as well as from the hydrochar leachate, P is precipitated in the form of struvite. Scenarios 1 and 2 both consider HTC and struvite production with the only difference that the hydrochar is used as a fuel instead of as a fertilizer in the latter case, and Scenario 3 adds leaching of the hydrochar with subsequent struvite production and considers that hydrochar is used as a fuel. In the fourth (reference) scenario, dewatering and drying of DPS is considered. The recovered product use in agriculture was not assessed at this stage. The assessment of the emerging technologies in Scenarios 1-3 was done by studying the technologies in early stages of development but modelling them as more developed in the future. Additional functions beyond the functional unit of one kg of P recovered were handled through a system expansion by substitution approach. This way, the system was credited for calcium ammonium nitrate (CAN) production in all scenarios and for wood chips production in Scenarios 2 and 3. Looking at net outcomes for all scenarios, the life cycle impact indicator results for scenario 2 are lower than the other scenarios in several impact categories. Large gains in scenario 2 are related to the avoided production of wood chips.
摘要：
磷矿是有限的，主要用于化肥生产的不可再生矿产资源。这种有限材料的稀缺性和日益增长的需求导致欧盟委员会在2014年将其列入关键原材料清单。因此,努力提高材料的使用效率，启动回收工作，并制定废物政策以减轻原材料的危害性。近年来，人们对开发从有机废物流中回收营养的技术的兴趣有所增加，乳制品加工污泥(DPS)是潜在的输入废物流。尽管从DPS中回收P可以促进社会中更多的营养物质循环流动，必须评估是否也有整体环境收益。本文报告了涉及水热碳化（HTC）和鸟粪石沉淀的三种磷（P）回收方案的环境影响的生命周期评估（LCA），并与参考干燥方案进行了比较。HTC产生固体部分（水炭），和液体部分(工艺用水)，在其中一个场景(场景3)中，考虑浸出水热炭以获得额外的P回收。从工艺用水以及水炭浸出液中，P以鸟粪石的形式沉淀。方案1和方案2都考虑了HTC和鸟粪石的生产，唯一的区别在于水炭在后一种情况下用作燃料而不是肥料。和方案3增加了水炭的浸出和随后的鸟粪石生产，并认为水炭用作燃料。在第四个（参考）场景中，考虑了DPS的脱水和干燥。在此阶段未评估回收产品在农业中的使用情况。对方案1-3中的新兴技术的评估是通过在开发的早期阶段研究技术，但将其建模为将来更发达的技术来完成的。通过替代方法进行系统扩展，可以处理超过回收的1千克P的功能单位的其他功能。这边,该系统在所有情况下都被认为是硝酸铵钙（CAN）的生产，在情况2和3中也被认为是木片的生产。查看所有场景的净结果，在几个影响类别中，情景2的生命周期影响指标结果低于其他情景。方案2中的大量收益与避免生产木片有关。
