Purpose

California’s Central Valley produces more than 75% of global commercial almond supply, making the life cycle performance of almond production in California of global interest. This article describes the life cycle assessment of California almond production using a Scalable, Process-based, Agronomically Responsive Cropping System Life Cycle Assessment (SPARCS-LCA) model that includes crop responses to orchard management and modeling of California’s water supply and biomass energy infrastructure.

Methods

A spatially and temporally resolved LCA model was developed to reflect the regional climate, resource, and agronomic conditions across California’s Central Valley by hydrologic subregion (San Joaquin Valley, Sacramento Valley, and Tulare Lake regions). The model couples a LCA framework with region-specific data, including water supply infrastructure and economics, crop productivity response models, and dynamic co-product markets, to characterize the environmental performance of California almonds. Previous LCAs of California almond found that irrigation and management of co-products were most influential in determining life cycle CO₂eq emissions and energy intensity of California almond production, and both have experienced extensive changes since previous studies due to drought and changing regulatory conditions, making them a focus of sensitivity and scenario analysis.

Results and discussion

Results using economic allocation show that 1 kg of hulled, brown-skin almond kernel at post-harvest facility gate causes 1.92 kg CO₂eq (GWP₁₀₀), 50.9 MJ energy use, and 4820 L freshwater use, with regional ranges of 2.0–2.69 kg CO₂eq, 42.7–59.4 MJ, and 4540–5150 L, respectively. With a substitution approach for co-product allocation, 1 kg almond kernel results in 1.23 kg CO₂eq, 18.05 MJ energy use, and 4804 L freshwater use, with regional ranges of 0.51–1.95 kg CO₂eq, 3.68–36.5 MJ, and 4521–5140 L, respectively. Almond freshwater use is comparable with other nut crops in California and globally. Results showed significant variability across subregions. While the San Joaquin Valley performed best in most impact categories, the Tulare Lake region produced the lowest eutrophication impacts.

Conclusion

While CO₂eq and energy intensity of almond production increased over previous estimates, so too did credits to the system for displacement of dairy feed. These changes result from a more comprehensive model scope and improved assumptions, as well as drought-related increases in groundwater depth and associated energy demand, and decreased utilization of biomass residues for energy recovery due to closure of bioenergy plants in California. The variation among different impact categories between subregions and over time highlight the need for spatially and temporally resolved agricultural LCA.

中文翻译：

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可扩展且时空解析的加利福尼亚杏仁农业生命周期评估

目的

加利福尼亚州的中央谷地生产了全球超过75％的全球商业杏仁供应量，这使加利福尼亚州杏仁生产的生命周期绩效引起了全球关注。本文介绍了使用可扩展的，基于过程的农用响应性作物系统生命周期评估（SPARCS-LCA）模型对加利福尼亚杏仁生产进行生命周期评估，该模型包括农作物对果园管理的响应以及加利福尼亚州供水和生物质能源基础设施的建模。

方法

建立了时空分解的LCA模型，以反映水文分区（加利福尼亚州圣华金河谷，萨克拉门托河谷和图莱里湖地区）跨加州中央谷地的区域气候，资源和农艺条件。该模型将LCA框架与特定地区的数据结合在一起，包括供水基础设施和经济，作物生产力响应模型以及动态副产品市场，以表征加利福尼亚杏仁的环境绩效。加利福尼亚杏仁的先前LCA发现，副产品的灌溉和管理对确定生命周期中的CO ₂影响最大自从先前的研究以来，由于干旱和法规条件的变化，加州杏仁产量的当量排放量和能量强度都经历了广泛的变化，这使它们成为敏感性和情景分析的重点。

结果与讨论

根据经济分配得出的结果表明，收获后设施门口的1千克去壳棕色皮肤杏仁仁引起1.92千克CO ₂当量（GWP ₁₀₀），50.9 MJ能源消耗和4820 L淡水利用，区域范围为2.0–分别为2.69 kg CO ₂当量，42.7-59.4 MJ和4540-5150L。采用副产品分配的替代方法，1公斤杏仁仁可产生1.23公斤CO ₂当量，18.05兆焦能源消耗和4804升淡水消耗，区域范围为0.51-1.95公斤CO ₂eq，分别为3.68–36.5 MJ和4521–5140L。杏仁淡水的使用量可与加利福尼亚州乃至全球的其他坚果作物相媲美。结果表明，各次区域之间存在显着差异。虽然圣华金河谷在大多数影响类别中表现最好，但图莱里湖地区的富营养化影响却最低。

结论

尽管杏仁生产的CO ₂当量和能量强度比以前的估计有所增加，但乳制品排量系统的功劳也得到了认可。这些变化的产生是由于更广泛的模型范围和改进的假设，以及与干旱相关的地下水深度和相关能源需求的增加，以及由于加利福尼亚州关闭了生物能源工厂而减少了生物质残渣用于能源回收的利用。次区域之间不同影响类别之间的差异以及随着时间的推移，突显了对在空间和时间上解析的农业生命周期评估的需求。