Purpose

Coffee cut-stems (CCS) are typically left in the field after coffee harvesting as fertilizer or used partially for cooking and drying of coffee grains. However, the energy contained in this residue is not completely exploited. For this reason, different applications for CCS have been considered to obtain innovative products. This work aims to evaluate the environmental impact of energy generation through two biorefinery systems using CCS as feedstock.

Methods

The life cycle assessment (LCA) considers a cradle-to-gate approach, beginning at the seed germination and ending at the production of ethanol, electricity, and low-pressure steam. Inventory data of the coffee production are collected from national reports. Mass and energy balances are calculated using an integrated methodological approach comprising the conceptual design and optimization of the CCS biorefineries.

Results and discussion

CCS production is one of the hotspots in both evaluated biorefineries due to the use of high amounts of fertilizers, contributing to most of the environmental impact categories. From the two assessed biorefinery configurations, the system with the lowest environmental benefits was the one that considered the generation of electricity and steam. Factors such as the high emissions of exhaust gases (mainly composed of CO₂) and the use of water for steam generation were the main contributors. The alternative solution I (AS-I) has the lowest environmental impact in comparison with the base case. From the sensitivity analyses, the use of energy allocation approach provided better performance than the system expansion approach. However, the selection of one approach over the other highly depends on the evaluated impact category based on the uncertainty analysis.

Conclusions

The production of CCS has the highest contribution to the overall environmental impact of the evaluated biorefineries, and thus, we need available information of the coffee crop production including the production of co-products, such as CCS. We present a detailed inventory of the production of CCS in Colombia as an important contribution for further research in the area of coffee-based biorefineries. Based on our inventory, the production of bioenergy (electricity and steam) for a coffee-based biorefinery seems to provide the best environmental performance in comparison to the production of biofuels (ethanol).

中文翻译：

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能源驱动型生物精炼厂的环境评估：哥伦比亚的咖啡干法（CCS）案例

目的

咖啡切茎（CCS）通常在咖啡收获后留在田间作为肥料，或部分用于煮熟和干燥咖啡粒。但是，残留物中所含的能量并未被完全利用。因此，已经考虑了CCS的不同应用来获得创新产品。这项工作旨在通过使用CCS作为原料的两个生物精炼系统评估能源生产对环境的影响。

方法

生命周期评估（LCA）考虑了从摇篮到大门的方法，该方法始于种子发芽，结束于乙醇，电力和低压蒸汽的产生。咖啡产量的库存数据是从国家报告中收集的。使用包括CCS生物精炼厂的概念设计和优化在内的综合方法学方法来计算质量和能量平衡。

结果和讨论

由于使用大量肥料，CCS生产是两个经过评估的生物精炼厂的热点之一，对大多数环境影响类别都有贡献。从两种经过评估的生物精炼厂配置中，具有最低环境效益的系统就是考虑发电和蒸汽的系统。诸如废气（主要由CO ₂组成）的高排放等因素）和使用水产生蒸汽是主要的贡献者。与基本方案相比，替代方案I（AS-I）对环境的影响最小。从灵敏度分析来看，与系统扩展方法相比，使用能量分配方法可提供更好的性能。但是，选择一种方法而不是另一种方法在很大程度上取决于根据不确定性分析评估的影响类别。

结论

CCS的生产对所评估的生物精炼厂的整体环境影响具有最大的贡献，因此，我们需要咖啡作物生产的可用信息，包括副产品的生产，例如CCS。我们提供了哥伦比亚CCS生产的详细清单，作为对基于咖啡的生物精炼领域的进一步研究的重要贡献。根据我们的库存，与生物燃料（乙醇）的生产相比，咖啡基生物精炼厂的生物能源（电力和蒸汽）生产似乎具有最佳的环保性能。