Simpson Thomas W, Sharpley Andrew N, Howarth Robert W, Paerl Hans W, Mankin Kyle R
Dep. of Environmental Science and Technology, Univ. of Maryland, College Park, MD 20742, USA.
J Environ Qual. 2008 Feb 11;37(2):318-24. doi: 10.2134/jeq2007.0599. Print 2008 Mar-Apr.
Renewable fuel production, particularly grain-based ethanol, is expanding rapidly in the USA. Although subsidized grain-based ethanol may provide a competitively priced transportation fuel, concerns exist about potential environmental impacts. This contribution focuses on potential water quality implications of expanded grain-based ethanol production and potential impacts of perennial-grass-based cellulosic ethanol. Expanded grain-based ethanol will increase and intensify corn production. Even with recommended fertilizer and land conservation measures, corn acreage can be a major source of N loss to water (20-40 kg ha(-1) yr(-1)). A greater acreage of corn is estimated to increase N and P loss to water by 37% (117 million kg) and 25% (9 million kg), respectively, and measures to encourage adoption of conservation practices are essential to mitigate water quality impairments. Dried distiller's grains remaining after ethanol production from corn grain are used as animal feed and can increase manure P content and may increase N content. Cellulosic fuel-stocks from perennials such as switchgrass and woody materials have the potential to produce ethanol. Although production, storage, and handling of cellulosic materials and conversion technology are limitations, accelerating development of cellulosic ethanol has the potential to reduce dependence on grain fuel-stocks and provide water quality and other environmental benefits. All alternative fuel production technologies could have environmental impacts. There is a need to understand these impacts to help guide policy and help make programmatic and scientific decisions that avoid or mitigate unintended environmental consequences of biofuel production.
可再生燃料生产，尤其是以谷物为原料的乙醇生产，在美国正迅速扩张。尽管补贴后的以谷物为原料的乙醇可能提供价格具有竞争力的运输燃料，但人们对其潜在的环境影响仍存在担忧。本文着重探讨扩大以谷物为原料的乙醇生产对水质的潜在影响以及多年生草本植物纤维素乙醇的潜在影响。扩大以谷物为原料的乙醇生产将增加并强化玉米种植。即便采取了推荐的肥料和土地保护措施，玉米种植面积仍可能是氮素流失到水体中的主要来源（每年每公顷20 - 40千克）。预计更大的玉米种植面积将分别使氮和磷流失到水体中的量增加37%（1.17亿千克）和25%（900万千克），因此鼓励采用保护措施对于减轻水质损害至关重要。玉米谷物生产乙醇后剩余的干酒糟用作动物饲料，会增加粪便中的磷含量，也可能增加氮含量。来自柳枝稷和木质材料等多年生植物的纤维素燃料原料有生产乙醇的潜力。尽管纤维素材料的生产、储存和处理以及转化技术存在局限性，但加速纤维素乙醇的开发有可能减少对谷物燃料原料的依赖，并带来水质和其他环境效益。所有替代燃料生产技术都可能产生环境影响。有必要了解这些影响，以帮助指导政策制定，并有助于做出规划和科学决策，避免或减轻生物燃料生产带来的意外环境后果。
