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Abstract：
Urban agriculture, while being a promising solution to increase food sovereignty in cities, can lead to an unprecedented discharge of nutrient and fertilizer-related emissions into the urban environment. Especially relevant are nitrogen (N) and phosphorus (P), due to their contribution to marine and freshwater eutrophication. Therefore, alternative methods of fertilization need to be put into practice to avoid such impacts to the surrounding environment. Struvite, has been studied as a potential slow releasing fertilizer due to its high P content, while the bacteria rhizobium has been used to fix N directly from the atmosphere. Legumes, like the common bean are N-demanding crops capable of symbiosis with the bacteria rhizobium and have previously shown positive responses to fertilization with struvite. This study aims to analyze the environmental performance of plant production in hydroponic systems combining rhizobium inoculation and struvite (2 g, 5 g, 10 g, 20 g) irrigated with a N and P deficient nutrient solution, using life cycle analysis (LCA). The nutrient content of in- and out-going irrigation was analyzed as well as in plants and beans. The functional unit for the LCA was 1 kg of fresh beans. The results obtained indicate a yield reduction of 60% to 50% in comparison to the control which was irrigated with a full nutrient solution. The impacts from operational stage are less in all impact categories, where most significant reductions up to 69% and 59% are seen in marine-eutrophication and global warming respectively. Although the infrastructure does not change between treatments, its impacts increase due to the lower yields. We determine that below a 10% of the control yield, the alternative systems have more impact than the use of conventional mineral fertilizers in almost all impact categories, thus pointing to the importance of infrastructure to truly reduce environmental impacts for urban agriculture.
摘要：
都市农业,虽然是增加城市粮食主权的一个有希望的解决方案，可能导致前所未有的养分和肥料相关排放排放到城市环境中。特别相关的是氮（N）和磷（P），由于它们对海洋和淡水富营养化的贡献。因此,需要将其他施肥方法付诸实践，以避免对周围环境的影响。Struvite,由于其高磷含量，已被研究为潜在的缓释肥料，而根瘤菌已被用来直接从大气中固定氮。豆类,像普通的豆类一样，需要N的作物能够与根瘤菌共生，并且以前对鸟粪石施肥表现出积极的反应。本研究旨在分析结合根瘤菌接种和鸟粪石的水培系统中植物生产的环境性能（2g，5g,10g,20g)用缺乏N和P的营养液灌溉，使用生命周期分析(LCA)。分析了进出灌溉以及植物和豆类中的养分含量。LCA的功能单位是1千克新鲜豆。获得的结果表明，与用全营养液灌溉的对照相比，产量降低了60％至50％。在所有影响类别中，运营阶段的影响较小，其中，海洋富营养化和全球变暖的降幅最大，分别达到69%和59%。虽然基础设施在治疗之间没有变化，由于产量较低，其影响增加。我们确定低于对照产量的10%，在几乎所有影响类别中，替代系统比使用常规矿物肥料具有更大的影响，因此指出了基础设施的重要性，以真正减少对城市农业的环境影响。
