With the progressive implementation of Low-Carbon Policies based on Life Cycle Assessment (LCA) methodologies to assess climate change mitigation, biofuels’ potential environmental advantages could finally be translated into economic revenues, especially for residue-based production chains. This implies, however, tackling environmental hotspots along the Life Cycle, such as the use of enzymes, an important input in cellulosic ethanol production. While relevant, however, aspects of enzyme manufacturing, crucial to the LCA results, are often oversimplified in databases or even undisclosed, which might render the accounting for this flow unreliable. A potential solution for this is to model enzyme production, disclosing aspects such as carbon source uptakes, energy consumption and purification steps, all of which may carry significant environmental burdens, especially for fossil-reliant procedures. Integrating these steps into the biorefinery process design as an on-site operation, however, would allow access to renewable energy and carbon sources for enzyme production, potentially reducing their burden in the final biofuel LCA profile, when compared with off-site supply. This work, then, aims to evaluate the effect of inserting on-site enzyme production within a stand-alone second-generation (2G) biorefinery, using sugarcane straw as feedstock, to produce ethanol and electricity, as opposed to off-site enzyme supply from manufacturers. The results show that adopting on-site production can reduce the overall environmental impact profile for cellulosic ethanol, in comparison to off-site supply, even though off-site data present significant variability among databases and literature. This trend persisted for varied enzyme dosages in the saccharification process and for different inventories to model off-site supply. The reference inventories for off-site supply lack transparency and details, while also displaying large discrepancies between impact indicators, indicating the need to pursue more consistent, reliable, and complete inventories for its modelling in LCA. Compared to first-generation (1G) sugarcane ethanol, 2G-ethanol (with on-site enzyme production) demonstrated a reduction in the Global Warming Potential category of around 80%. However, relevant trade-offs for 2G ethanol (with off-site enzyme supply) were observed – regarding ecotoxicity, mineral scarcity, eutrophication and even the potential GHG reduction – when different enzyme inventories are used.

随着基于生命周期评估 (LCA) 方法评估气候变化减缓的低碳政策的逐步实施，生物燃料的潜在环境优势最终可以转化为经济收入，特别是对于基于残渣的生产链。然而，这意味着要解决生命周期中的环境热点问题，例如酶的使用，这是纤维素乙醇生产的重要投入. 然而，尽管相关，但对 LCA 结果至关重要的酶制造方面通常在数据库中被过度简化甚至未公开，这可能会导致对该流程的解释不可靠。一个潜在的解决方案是模拟酶的生产，揭示碳源吸收、能源消耗和纯化步骤等方面，所有这些都可能带来重大的环境负担，特别是对于依赖化石的程序。将这些步骤整合到生物精炼厂中然而，作为现场操作的工艺设计将允许获得用于酶生产的可再生能源和碳源，与场外供应相比，可能会减少它们在最终生物燃料 LCA 配置文件中的负担。因此，这项工作旨在评估在独立的第二代 (2G) 生物精炼厂中插入现场酶生产的效果，使用甘蔗秸秆作为原料生产乙醇和电力，而不是场外酶供应来自制造商。结果表明，采用现场生产可以降低纤维素乙醇的整体环境影响，与异地供应相比，即使异地数据在数据库和文献之间存在显着差异。这种趋势持续存在于糖化过程中不同的酶剂量和不同的库存以模拟场外供应。异地供应的参考清单缺乏透明度和细节，同时影响指标之间也存在较大差异，表明需要为其在 LCA 建模中追求更加一致、可靠和完整的清单。与第一代 (1G)甘蔗乙醇, 2G-乙醇（现场酶生产）表明全球变暖潜能值类别减少了约 80%。然而，当使用不同的酶库存时，观察到 2G 乙醇（与场外酶供应）的相关权衡 - 关于生态毒性、矿物质稀缺、富营养化甚至潜在的温室气体减少。