Williams Pamela R D, Inman Daniel, Aden Andy, Heath Garvin A
E Risk Sciences, LLP, 4647 Carter Trail, Boulder, Colorado 80301, USA.
Environ Sci Technol. 2009 Jul 1;43(13):4763-75. doi: 10.1021/es900250d.
In this paper, we assess what is known or anticipated about environmental and sustainability factors associated with next-generation biofuels relative to the primary conventional biofuels (i.e., corn grain-based ethanol and soybean-based diesel) in the United States during feedstock production and conversion processes. Factors considered include greenhouse (GHG) emissions, air pollutant emissions, soil health and quality, water use and water quality, wastewater and solid waste streams, and biodiversity and land-use changes. Based on our review of the available literature, we find that the production of next-generation feedstocks in the U.S. (e.g., municipal solid waste, forest residues, dedicated energy crops, microalgae) are expected to fare better than corn-grain or soybean production on most of these factors, although the magnitude of these differences may vary significantly among feedstocks. Ethanol produced using a biochemical or thermochemical conversion platform is expected to result in fewer GHG and air pollutant emissions, but to have similar or potentially greater water demands and solid waste streams than conventional ethanol biorefineries in the U.S. However, these conversion-related differences are likely to be small, particularly relative to those associated with feedstock production. Modeling performed for illustrative purposes and to allow for standardized quantitative comparisons across feedstocks and conversion technologies generally confirms the findings from the literature. Despite current expectations, significant uncertainty remains regarding how well next-generation biofuels will fare on different environmental and sustainability factors when produced on a commercial scale in the U.S. Additional research is needed in several broad areas including quantifying impacts, designing standardized metrics and approaches, and developing decision-support tools to identify and quantify environmental trade-offs and ensure sustainable biofuels production.
在本文中，我们评估了与美国下一代生物燃料相关的环境和可持续性因素，这些因素相对于主要的传统生物燃料（即以玉米谷物为原料的乙醇和以大豆为原料的柴油）在原料生产和转化过程中的情况。所考虑的因素包括温室气体（GHG）排放、空气污染物排放、土壤健康和质量、用水和水质、废水和固体废物流，以及生物多样性和土地利用变化。基于我们对现有文献的综述，我们发现美国下一代原料（如城市固体废物、森林残留物、专用能源作物、微藻）的生产在这些因素中的大多数方面预计会比玉米谷物或大豆生产表现更好，尽管这些差异的程度在不同原料之间可能有很大差异。使用生化或热化学转化平台生产的乙醇预计会产生较少的温室气体和空气污染物排放，但与美国传统乙醇生物精炼厂相比，其用水需求和固体废物流可能相似或更大。然而，这些与转化相关的差异可能很小，特别是相对于与原料生产相关的差异而言。为说明目的而进行的建模以及为了能够对不同原料和转化技术进行标准化定量比较的建模，总体上证实了文献中的研究结果。尽管有当前的预期，但在美国大规模生产下一代生物燃料时，其在不同环境和可持续性因素方面的表现究竟如何仍存在重大不确定性。在几个广泛领域还需要进一步研究，包括量化影响、设计标准化指标和方法，以及开发决策支持工具，以识别和量化环境权衡并确保可持续的生物燃料生产。
