Abstract：
The production of biogas from microalgae has gained attention due to their rapid growth, CO2 sequestration, and minimal land use. This study uses life cycle assessment to assess the environmental impacts of biogas production from wastewater-grown microalgae through anaerobic digestion within an optimized microalgae-based system. Using SimaPro® 9 software, 3 scenarios were modeled considering the ReCiPe v1.13 midpoint and endpoint methods for environmental impact assessment in different categories. In the baseline scenario (S1), a hypothetical system for biogas production was considered, consisting of a high rate algal pond (HRAP), a settling, an anaerobic digester, and a biogas upgrading unit. The second scenario (S2) included strategies to enhance biogas yield, namely co-digestion and thermal pre-treatment. The third scenario (S3), besides considering the strategies of S2, proposed the biogas upgrading in the HRAP and the digestate recovery as a biofertilizer. After normalization, human carcinogenic toxicity was the most positively affected category due to water use in the cultivation step, accounted as avoided product. However, this category was also the most negatively affected by the impacts of the digester heating energy. Anaerobic digestion was the most impactful step, constituting on average 60.37% of total impacts. Scenario S3 performed better environmentally, primarily due to the integration of biogas upgrading within the cultivation reactor and digestate use as a biofertilizer. Sensitivity analysis highlighted methane yield\'s importance, showing potential for an 11.28% reduction in ionizing radiation impacts with a 10% increase. Comparing S3 biogas with natural gas, the resource scarcity impact was reduced sixfold, but the human health impact was 23 times higher in S3.
摘要：
由于微藻的快速生长，其沼气的生产受到了人们的关注，二氧化碳封存，和最少的土地使用。本研究使用生命周期评估来评估通过优化的微藻系统中厌氧消化从废水生长的微藻产生沼气的环境影响。使用SimaPro®9软件,考虑到不同类别的环境影响评估的ReCiPev1.13中点和终点方法，对3种方案进行了建模。在基线场景(S1)中，考虑了一个假想的沼气生产系统，由一个高速率藻类池塘（HRAP）组成，一个沉降，厌氧消化器,和一个沼气升级装置。第二种情况(S2)包括提高沼气产量的策略，即共消化和热预处理。第三种情况（S3），除了考虑S2的策略外，还提出了HRAP中的沼气升级和将消化物回收作为生物肥料。归一化后,由于在栽培步骤中用水，人类致癌毒性是受影响最积极的类别，占避免的产品。然而,这一类也是受消化器加热能量影响最大的负面影响。厌氧消化是影响最大的一步,平均占总影响的60.37%。场景S3在环境方面表现更好，主要是由于沼气升级整合在培养反应器和消化物用作生物肥料。敏感性分析强调了甲烷产量的重要性，显示出电离辐射影响减少11.28%的潜力，增加10%。将S3沼气与天然气进行比较，资源稀缺的影响减少了六倍，但S3对人类健康的影响要高出23倍。
