Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia.
School of Agriculture and Food Science, The University of Queensland, Brisbane, Queensland 4072, Australia.
Sci Total Environ. 2021 Nov 20;796:148913. doi: 10.1016/j.scitotenv.2021.148913. Epub 2021 Jul 10.
Agriculture has radically changed the global nitrogen (N) cycle and is heavily dependent on synthetic N-fertiliser. However, the N-use efficiency of synthetic fertilisers is often only 50% with N-losses from crop systems polluting the biosphere, hydrosphere and atmosphere. To address the large carbon and energy footprint of N-fertiliser synthesis and curb N-pollution, new technologies are required to deliver enhanced energy efficiency, decarbonisation and a circular nutrient economy. Algae fertilisers (AF) are an alternative to synthetic N-fertiliser (SF). Here microalgae were used as biofertiliser for spinach production. AF production was evaluated using life-cycle analyses. Over 4 weeks, AF released 63.5% of N as bioavailable ammonium and nitrate, and 25% of phosphorous (P) as phosphate to the growth substrate; SF released 100% N and 20% P. To maximise crop N-use and minimise N-leaching, we explored AF and SF dose-response-curves with spinach in glasshouse conditions. AF-grown spinach produced 36% less biomass than SF-grown plants due to AF's slower and linear N-release; SF exhibited 5-times higher N-leaching than AF. Optimised AF:SF blends yielded greater synchrony between N-release and crop-uptake, boosting crop yields and minimising N-loss. Additional benefits of AF included greener leaves, lower leaf nitrate concentration, and higher microbial diversity and water holding capacity of the growth substrate. An integrated techno-economic and life-cycle-analysis of scaled-up microalgae systems (+/- wastewater) normalised to the application dose showed that replacing the most effective SF-dose with AF lowered the annual carbon footprint of fertiliser production from 3.644 kg CO m (C-producing) to -6.039 kg CO m (C-assimilation). N-loss from growth substrate was lowered by 54%. Embodied energy for AF:SF blends could be reduced by 29% when cultivating microalgae on wastewater. Conclusions: (i) microalgae offer a sustainable alternative to synthetic N-fertiliser for spinach production and potentially other crop systems, (ii) microalgae biofertilisers support the circular-nutrient-economy and several UN-Sustainable-Development-Goals.
农业已经彻底改变了全球氮（N）循环，并且严重依赖合成氮肥。然而，合成肥料的氮利用率通常只有 50%，农田系统的氮损失会污染生物圈、水圈和大气。为了解决氮肥合成的高碳和高能耗问题，并遏制氮污染，需要开发新技术来提高能源效率、减少碳排放并实现循环养分经济。藻类肥料（AF）是合成氮肥（SF）的替代品。在这里，微藻被用作菠菜生产的生物肥料。使用生命周期分析评估了 AF 的生产。在 4 周的时间里，AF 以生物可利用的铵盐和硝酸盐形式释放了 63.5%的 N，以磷酸盐形式释放了 25%的 P 到生长基质中；SF 释放了 100%的 N 和 20%的 P。为了最大限度地提高作物氮素利用率并减少氮淋失，我们在温室条件下用菠菜探索了 AF 和 SF 的剂量-反应曲线。由于 AF 的氮释放缓慢且呈线性，因此用 AF 种植的菠菜生物量比用 SF 种植的菠菜少 36%；SF 的氮淋失量比 AF 高 5 倍。优化的 AF:SF 混合物使氮释放和作物吸收之间更加同步，从而提高了作物产量并减少了氮损失。AF 的其他好处包括叶片更绿、叶片硝酸盐浓度更低、生长基质中的微生物多样性和持水能力更高。对规模化微藻系统（+/- 废水）进行技术经济和生命周期分析，并归一化为应用剂量后表明，用 AF 替代最有效的 SF 剂量可将肥料生产的年碳足迹从 3.644kgCO m（产生 C）降低至-6.039kgCO m（吸收 C）。生长基质中的氮损失减少了 54%。当在废水中培养微藻时，AF:SF 混合物的隐含能量可减少 29%。结论：（i）微藻为菠菜生产和潜在的其他作物系统提供了一种可持续的合成氮肥替代品，（ii）微藻生物肥料支持循环养分经济和几个联合国可持续发展目标。
