Institute for Technology and Resources Management in the Tropics and Subtropics (ITT), TH Köln (University of Applied Sciences), Germany.
Institute for Technology and Resources Management in the Tropics and Subtropics (ITT), TH Köln (University of Applied Sciences), Germany.
J Environ Manage. 2021 Jul 15;290:112557. doi: 10.1016/j.jenvman.2021.112557. Epub 2021 Apr 14.
Due to the amendment of the sewage sludge ordinance, both a thermal post-treatment and a phosphorous recovery from sewage sludge will become mandatory for large-scale wastewater treatment plants in Germany. This study analyzed four prospective treatment paths for sewage sludge by means of life cycle assessment. In the realm of a gate-to-cradle approach, environmental impacts were quantified for all compartments of the ReCiPe Midpoint (H) 2016 method. The spreading of digested sludge on agricultural soils was considered as the base case (system: AD + spreading). It was compared to the centralized incineration of sludge (system: AD + I), a decentralized hydrothermal carbonization followed by centralized incineration (system: AD + HTC + I) and a decentralized pyrolysis of sludge followed by centralized incineration (system: AD + P + I). For all cases, phosphorous recovery from the ash was included. A comparative evaluation showed that AD + spreading resulted in least environmental impacts in most categories but was subject to a high local immission potential due to sewage sludge spreading. It was found to be only justifiable, if toxicity and eutrophication were not compromised. Alternatively, a thermal post-treatment step is required. Hereby, AD + I and AD + HTC + I showed the overall least environmental impacts, while AD + P + I was characterized by similar or higher environmental impacts throughout all impact categories. Alongside the comparative analysis, a hotspot analysis was carried out and mitigation potentials were identified. For all thermochemical post-treatment paths, it was derived that (i) the share of fossil external energy must be kept to a minimum, (ii) primary or secondary measures to control NO emissions during the incineration and pyrolysis should be implemented and (iii) the technological approach to recover phosphorous must be carefully selected.
由于污水污泥条例的修订，德国大型废水处理厂都必须对污水污泥进行热后处理和磷回收。本研究通过生命周期评估分析了污水污泥的四种潜在处理途径。在从摇篮到大门的方法中，使用 ReCiPe 中点 (H) 2016 方法的所有部分量化了环境影响。将消化污泥施用于农业土壤被认为是基准情况（系统：AD+ 施撒）。将其与污泥集中焚烧（系统：AD+I）、分散式水热碳化后集中焚烧（系统：AD+HTC+I）和分散式污泥热解后集中焚烧（系统：AD+P+I）进行了比较。对于所有情况，都包括了从灰分中回收磷。比较评估表明，在大多数类别中，AD+施撒的环境影响最小，但由于污泥施撒，存在高局部排放潜势。只有在不损害毒性和富营养化的情况下，AD+施撒才具有合理性。或者，需要进行热后处理。在这种情况下，AD+I 和 AD+HTC+I 显示出总体上最小的环境影响，而 AD+P+I 在所有影响类别中都具有相似或更高的环境影响。除了比较分析外，还进行了热点分析并确定了缓解潜力。对于所有热化学后处理途径，都得出以下结论：(i) 必须将化石外部能源的份额保持在最低水平，(ii) 应实施初级或二级措施来控制焚烧和热解过程中的氮排放，以及 (iii) 必须仔细选择回收磷的技术方法。
