A growing world population with increasing levels of food consumption will lead to more dairy and swine production and increasing amount of manure that requires treatment. Discharge of excessive nutrients and carbon in untreated animal manure can lead to greenhouse gas emissions and eutrophication concerns, and treatment efforts can be expensive for small scale farmers in marginalized communities. The overall goal of this study was to determine the environmental and economic sustainability of four animal manure management scenarios in Costa Rica: (1) no treatment, (2) biodigesters, (3) biodigesters and struvite precipitation, and (4) biodigesters, struvite precipitation, and lagoons. Life cycle assessment was used to assess the carbon footprint and eutrophication potential, whereas life cycle cost analysis was used to evaluate the equivalent uniform annual worth over the construction and operation and maintenance life stages. Recovery of biogas as a cooking fuel and recovery of nutrients from the struvite reactor reduced the carbon footprint, leading to carbon offsets of up to 2,500 kg CO₂ eq/year. Offsets were primarily due to avoiding methane emissions during energy recovery. Eutrophication potential decreased as resource recovery processes were integrated, primarily due to improved removal of phosphorus in effluent waters. Resource recovery efforts led to equivalent uniform annual benefits of $825 to $1,056/year, which could provide a helpful revenue source for lower-income farmers. This research can provide clarity on how small-scale farmers in marginalized settings can utilize resource recovery technologies to better manage animal manure, while improving economic and environmental sustainability outcomes.

中文翻译：

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通过资源回收改善边缘化农业社区动物粪便管理的生命周期经济和环境可持续性

随着世界人口的增长，食品消费水平的提高，将导致更多的奶牛和猪生产以及需要治疗的粪便数量增加。未经处理的动物粪便中过多的养分和碳的排放会导致温室气体排放和富营养化问题，而且对于边缘化社区的小规模农民而言，处理工作的成本可能很高。这项研究的总体目标是确定哥斯达黎加的四种动物粪便管理方案的环境和经济可持续性：（1）不进行处理，（2）生物消化物，（3）生物消化物和鸟粪石沉淀以及（4）生物消化物，鸟粪石降水和泻湖。使用生命周期评估来评估碳足迹和富营养化潜力，而生命周期成本分析则用于评估在建造，运营和维护生命周期内的等效年均价值。回收作为烹饪燃料的沼气和从鸟粪石反应器中回收养分减少了碳足迹，导致碳抵消量高达2500千克一氧化碳₂ eq /年。抵消主要是由于在能源回收过程中避免了甲烷排放。随着资源回收过程的整合，富营养化的潜力降低了，这主要是由于污水中磷的去除率提高了。资源恢复的努力使每年的均等收益为825美元至1,056美元，这可以为低收入农民提供有用的收入来源。这项研究可以澄清边缘化地区的小规模农民如何利用资源回收技术更好地管理动物粪便，同时改善经济和环境可持续性成果。