Abstract：
Sugarcane straw removal for bioenergy production will increase substantially in the next years, but this may deplete soil organic carbon (SOC) and exacerbate greenhouse gas (GHG) emissions. These aspects are not consistently approached in bioenergy life cycle assessment (LCA). Using SOC modeling and LCA approach, this study addressed the life cycle GHG balance from sugarcane agroindustry in different scenarios of straw removal, considering the potential SOC changes associated with straw management in sugarcane-cultivated soils in Brazil. Long-term simulations showed SOC losses of up to -0.5 Mg ha-1 yr-1 upon complete straw removal, whereas the moderate removal had little effects on SOC and the maintenance of all straw in the field increased SOC accumulation by up to 0.4 Mg ha-1 yr-1. Our analysis suggests that accounting for SOC changes in LCA calculations could lower the net GHG benefits of straw-derived bioenergy, whose emissions intensity varied according to soil type. Overall, SOC depletion induced by complete straw removal increased the life cycle GHG emissions of straw-derived bioenergy by 26 % (3.9 g CO2eq MJ-1) compared to a scenario without taking SOC changes into account. Straw removal for cellulosic ethanol could be effective for mitigating GHG emissions relative to gasoline, but it was not advantageous for bioelectricity generation depending on the energy sources that are displaced. Therefore, straw-induced change of SOC stocks is a critical factor to model life cycle GHG emissions of straw-derived bioenergy.
摘要：
未来几年，用于生物能源生产的甘蔗秸秆去除将大幅增加，但这可能会消耗土壤有机碳（SOC）并加剧温室气体（GHG）排放。在生物能源生命周期评估(LCA)中，这些方面并不一致。使用SOC建模和LCA方法，这项研究探讨了不同秸秆去除方案下甘蔗农业产业的生命周期温室气体平衡，考虑到巴西甘蔗种植土壤中与秸秆管理相关的潜在SOC变化。长期模拟显示，完全清除秸秆后，SOC损失高达-0.5Mgha-1yr-1，而适度去除对SOC的影响很小，在田间维持所有秸秆可使SOC积累增加0.4Mgha-1yr-1。我们的分析表明，考虑LCA计算中的SOC变化可能会降低秸秆衍生生物能源的温室气体净收益，其排放强度根据土壤类型而变化。总的来说,与不考虑SOC变化的情况相比，完全清除秸秆引起的SOC消耗使秸秆衍生生物能源的生命周期温室气体排放量增加了26％（3.9gCO2eqMJ-1）。秸秆去除纤维素乙醇可以有效减少温室气体相对于汽油的排放，但是这对生物发电来说并不有利，这取决于被取代的能源。因此,秸秆引起的SOC存量变化是模拟秸秆衍生生物能源生命周期温室气体排放的关键因素。
