Civil and Environmental Engineering and ‡McIntire School of Commerce, University of Virginia, Charlottesville, Virginia 22904, United States.
Environ Sci Technol. 2011 Sep 1;45(17):7554-60. doi: 10.1021/es200760n. Epub 2011 Aug 3.
Algae are a widely touted source of bioenergy with high yields, appreciable lipid contents, and an ability to be cultivated on marginal land without directly competing with food crops. Nevertheless, recent work has suggested that large-scale deployment of algae bioenergy systems could have unexpectedly high environmental burdens. In this study, a "well-to-wheel" life cycle assessment was undertaken to evaluate algae's potential use as a transportation energy source for passenger vehicles. Four algae conversion pathways resulting in combinations of bioelectricity and biodiesel were assessed for several relevant nutrient procurement scenarios. Results suggest that algae-to-energy systems can be either net energy positive or negative depending on the specific combination of cultivation and conversion processes used. Conversion pathways involving direct combustion for bioelectricity production generally outperformed systems involving anaerobic digestion and biodiesel production, and they were found to generate four and fifteen times as many vehicle kilometers traveled (VKT) per hectare as switchgrass or canola, respectively. Despite this, algae systems exhibited mixed performance for environmental impacts (energy use, water use, and greenhouse gas emissions) on a "per km" basis relative to the benchmark crops. This suggests that both cultivation and conversion processes must be carefully considered to ensure the environmental viability of algae-to-energy processes.
藻类是一种广受推崇的生物能源来源，具有高产量、可观的脂质含量，并且能够在边际土地上种植，而不会与粮食作物直接竞争。然而，最近的研究表明，大规模部署藻类生物能源系统可能会带来意想不到的高环境负担。在这项研究中，进行了“从摇篮到车轮”的生命周期评估，以评估藻类作为乘用车运输能源的潜力。针对几种相关的营养物采购方案，评估了导致生物电能和生物柴油组合的四种藻类转化途径。结果表明，藻类能源系统的净能量产出可能为正，也可能为负，具体取决于所使用的具体培养和转化过程的组合。涉及直接燃烧生产生物电能的转化途径通常优于涉及厌氧消化和生物柴油生产的系统，并且发现它们每公顷产生的车辆行驶里程（VKT）分别是柳枝稷或油菜籽的四倍和十五倍。尽管如此，藻类系统在“每公里”的基础上相对于基准作物在环境影响（能源使用、水使用和温室气体排放）方面的表现参差不齐。这表明，必须仔细考虑培养和转化过程，以确保藻类到能源过程的环境可行性。
