The regular addition of plant-available nutrients such as nitrogen and phosphorus, either as manufactured fertilisers or animal manure, to agricultural soils is needed for global food security. Increased recycling of nutrients back to agriculture from organic waste streams is necessary for increased rural–urban sustainability. Anaerobic digestion of sewage sludge and agricultural wastes is widely applied to stabilize the substrate and also capture its energetic value via biogas production. The liquid phase of anaerobic digestate is a concentrated source of nutrients to which nutrient recovery technologies can be applied. Two such promising technologies that could increase nutrient recycling from e.g. wastewater and thereby contribute to environmental amelioration are struvite precipitation and ammonia stripping. By combining anaerobic digestion and nutrient recovery technologies on the digestate, a treatment process that provides both renewable energy and plant nutrients is achieved. This review will examine the effectiveness of ecotechnologies for the recovery and reuse of nitrogen and phosphorus from anaerobic digestate with the aim of reducing the impact of waste on the environment. We will search for both academic and grey literature published after 2013. English language searches will be performed in 4 bibliographic databases, and Google Scholar, while searches in 41 specialist websites will be performed in English, Finnish, Polish and Swedish. Eligibility screening will be conducted at two levels: title and abstract and full text. Included eligible studies will be subject to a critical appraisal that will assess external and internal study validity. We will extract information on study characteristics, intervention, comparators, effect modifiers, and measured outcomes. Data synthesis will involve narrative synthesis of each included study of sufficient validity. Quantitative synthesis (i.e. meta-analysis) may be possible in cases where a sufficient number of studies report similar types of outcomes.

中文翻译：

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从厌氧消化物中回收氮和磷的生态技术的有效性以及作为肥料的回收产品的有效性：系统审查协议

为了全球粮食安全，需要向农业土壤中定期添加植物可利用的营养素，例如人造肥料或动物肥料中的氮和磷。增加养分从有机废物流回农业的回收对于提高城乡可持续性是必要的。污水污泥和农业废料的厌氧消化被广泛用于稳定基质，并通过沼气生产获得其能量价值。厌氧消化液的液相是营养物的集中来源，可以应用营养物回收技术。鸟粪石沉淀和氨汽提是两种有前途的技术，它们可以增加废水中养分的循环利用，从而有助于改善环境。通过在消化液上结合厌氧消化和养分回收技术，可以实现提供可再生能源和植物养分的处理过程。这篇综述将研究生态技术从厌氧消化物中回收和再利用氮和磷的有效性，以减少废物对环境的影响。我们将搜索2013年以后出版的学术和灰色文献。英语搜索将在4个书目数据库和Google Scholar中进行，而41个专业网站的搜索将以英语，芬兰语，波兰语和瑞典语进行。资格筛选将在两个级别进行：标题和摘要以及全文。纳入的合格研究将接受评估，以评估外部和内部研究的有效性。我们将提取有关研究特征，干预措施，比较者，影响因子和测量结果的信息。数据综合将包括对每个纳入研究的足够有效性的叙述性综合。在足够多的研究报告相似结果类型的情况下，可能可以进行定量综合（即荟萃分析）。