Implications of removing straw from soil for bioenergy: An LCA of ethanol production using total sugarcane biomass
Implications of removing straw from soil for bioenergy: An LCA of ethanol production using total sugarcane biomass
复制标题
DOI：
10.1016/j.jclepro.2018.01.119
复制
发表时间：
2018-04-20
影响因子：
11.1
通讯作者：
Machado, Frederico S.
中科院分区：
文献类型：
--
作者：
Caldeira-Pires, Armando;Benoist, Anthony;Machado, Frederico S.
生物参数的变化，主要是与土地利用有关的参数的变化，是评估生物能源生产的温室气体(GHG)平衡的一个基本问题。从2002年到2017年，巴西从手工甘蔗收获向机械化甘蔗收获的过渡带来了10-20毫克公顷(-1)年(-1)的生物量，通过生物电力增加了150%的收入。本研究是利用秸秆和蔗渣生产生物乙醇的生命周期评估(LCA)。评估的重点是全球变暖潜力(GWP)，描述了生物和化石碳流的特征，该功能单元为1 MJ，96%的水合生物乙醇生产，如在Gabi建模。该模型基于一个具体的从摇篮到大门的巴西国家石油公司农用工业部门的原始数据。生物流包括对二氧化碳的吸收和农业和工业排放。参数方程描述了秸秆还田对甘蔗产量和土壤碳排放的影响。然后评估其余的CML影响类别。研究了两种秸秆利用方案：秸秆留在地里的参考系(RS)和秸秆转锅炉系统(SS)，在SS中，秸秆的部分或全部输出用于能量转换。通过考虑秸秆对蔗汁含糖量的影响和在蔗渣和秸秆均被水解的基础上使用第二代乙醇装置(2G)，进行了两种敏感性分析。在RS中，55%的碳被甘蔗(甘蔗渣+果汁)捕获，45%的碳被秸秆捕获。农业温室气体产量分布在酒糟(9.2%)和秸秆还田(7.6%)之间。工业温室气体排放包括焚烧甘蔗渣(46%)、发酵排放(11%)和嵌入乙醇的预排放96%(26%)。在SS 100%的情况下，GWP增加了161%，生物GWP从土壤转移到锅炉。此外，由于只使用了初始种植面积的86%，化石燃料全球变暖潜能值减少了39%。这些结果突显了这样一个事实，即当使用捕获的碳生产相同的功能单元或乙醇和电力相结合的技术产品时，去除秸秆作为额外的生物质发电与随之而来的更高的甘蔗产量和整体更高的环境性能和效率相关。在SA方案中，GWP与转化为乙醇的糖的+/-10%的变化直接相关。在2G场景下，GWP结果显示，第二代生物质能源必须优化秸秆用量。其他类别在情景之间显示出类似的质量变化，这些情景与化石和矿物储备加工或与额外的锅炉排放有关。(C)2018爱思唯尔有限公司。保留所有权利。
Changes in biotic parameters, primarily in those associated with land use, are a fundamental issue for assessing the greenhouse gas (GHG) balance of bioenergy production. From 2002 to 2017, the transition from manual to mechanized sugarcane harvesting in Brazil resulted in 10-20 Mg ha(-1) y(-1) of biomass, increasing incomes by 150% via bioelectricity. This study is a life cycle assessment (LCA) of using straw along with bagasse for bioethanol production. The assessment focused on the global warming potential (GWP), characterizing the biotic and fossil carbon flows for a functional unit of 1 MJ of 96% hydrated bioethanol production as modeled in GaBi. The model is based on the primary data for a specific cradle to-gate Petrobras agro-industrial unit. The biotic flow includes the CO2 uptake and the agricultural and industrial emissions. The parametric equations depict the influence of leaving straw in the field on the sugarcane yield and the soil carbon emissions. The remaining CML impact categories are then assessed. Two straw utilization scenarios were studied as follows: the reference system (RS), in which straw is left in the field, and the straw-to-boiler system (SS), in which part or all of the straw is exported for energy conversion. Two sensitivity analyses were performed by considering the effect of the straw on the amount of sugar in the sugarcane juice (SA) and considering the use of a second-generation ethanol unit (2G) on the basis of the hydrolysis of both bagasse and straw. In the RS, 55% of the carbon is captured in the sugarcane (bagasse + juice), and 45% is captured in the straw. The agricultural GHG output is distributed between vinasse fertigation (9.2%) and the straw left on the soil (7.6%). The industrial GHG emissions include the burning of bagasse (46%), fermentation emissions (11%) and the pre-emissions embedded in EtOH 96% (26%). In the SS 100% scenario, the GWP increases by 161%, with the biotic GWP shifting from soil to boiler. In addition, the fossil fuel GWP decreases by 39% due to the use of only 86% of the initial planting area. These results highlight the fact that removing straw to use as extra biomass for electricity is associated with a consequent higher sugarcane yield with an overall higher environmental performance and efficiency when using the captured carbon to produce the same functional unit or the combined ethanol and electricity technological products. In the SA scenario, the GWP is directly correlated with the imposed +/- 10% variation in the sugar that is transformed into ethanol. In the 2G scenario, the GWP results show that second-generation bioenergy must optimize the amount of straw. The other categories show similar qualitative variations among the scenarios, which are related to fossil and mineral reserve processing or to additional boiler emissions. (C) 2018 Elsevier Ltd. All rights reserved.