一项新的研究表明，生物燃料的生产可能会增加温室气体的排放。该研究的第一作者、诺贝尔奖获得者Paul Crutzen和来自欧美的同事认为，生产生物燃料作物所需的氮肥可能导致比人们此前所认为的更大数量的一氧化二氮排放到大气中。
根据这项研究，微生物把化肥中的3%到5%的氮转化成了一氧化二氮，而不是政府间气候变化委员会所估计的1%。
一氧化二氮是一种主要的温室气体，在100年的尺度上，它影响全球变暖的潜力是二氧化碳的296倍。
油菜籽产生的一氧化二氮导致的全球变暖，其数值是由于节省相应的化石燃料二氧化碳排放导致的“变冷”效应的1到1.7倍。对于玉米，这个数字是0.9到1.5，这表明或许应该继续使用石油而不是生产和燃烧生物燃料。
甘蔗是唯一一种表现出可以让温室气体排放净减少的作物，因为它需要的化肥少于其他生物燃料作物。
巴西是世界上最大的甘蔗生产国，它已经在乙醇制造和生物燃料使用上进行了大量投资。根据巴西地理与统计研究所的数据，在2006-2007年，巴西的甘蔗产量已经达到了4.25亿吨。
巴西农业气象与气候研究中心的农业工程师兼研究员Jurandir Zullo Jr说Crutzen等人的研究意义重大，但是在计算生物燃料的温室气体排放的时候，还需要考虑其他许多因素，包括从化学因素、社会因素到经济因素。
他还说如果这些结论得到了证实，那么它将会进一步鼓励巴西的甘蔗生产。然而，甘蔗种植面积的扩张可能进一步鼓励森林砍伐，而森林的减少也会造成全球变暖。
该研究发表在了《大气化学和物理学》杂志上。
原始出处：
Atmos. Chem. Phys. Discuss., 7, 11191–11205, 2007
N2O release from agro-biofuel production negates global warming reduction by replacing fossil fuels
P. J. Crutzen1,2,3, A. R. Mosier4, K. A. Smith5, and W. Winiwarter3,6
1Max Planck Institute for Chemistry, Department of Atmospheric Chemistry, Mainz, Germany
2Scripps Institution of Oceanography, University of California, La Jolla, USA
3International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria
4Mount Pleasant, SC, USA
5School of Geosciences, University of Edinburgh, Edinburgh, UK
6Austrian Research Centers – ARC, Vienna, Austria
Received: 28 June 2007 – Accepted: 19 July 2007 – Published: 1 August 2007
Correspondence to: P. J. Crutzen (crutzen@mpch-mainz.mpg.de)
Abstract
The relationship, on a global basis, between the amount of N fixed by chemical, biological or atmospheric processes entering the terrestrial biosphere, and the total emission of nitrous oxide (N2O), has been re-examined, using known global atmospheric removal rates and concentration 5 growth of N2O as a proxy for overall emissions. The relationship, in both the pre-industrial period and in recent times, after taking into account the large-scale changes in synthetic N fertiliser production and deforestation, is consistent, showing an overall conversion factor of 3–5%. This factor is covered only in part by the 1% of “direct” emissions from agricultural crop lands estimated by IPCC 10 (2006), or the “indirect” emissions cited therein. This means that the extra N2O entering the atmosphere as a result of using N to produce crops for biofuels will also be correspondingly greater than that estimated just on the basis of IPCC (2006). When the extra N2O emission from biofuel production is calculated in “CO2-equivalent” global warming terms, and compared with the quasi-cooling effect of “saving” emissions of 15 fossil fuel derived CO2, the outcome is that the production of commonly used biofuels, such as biodiesel from rapeseed and bioethanol from corn (maize), can contribute as much or more to global warming by N2O emissions than cooling by fossil fuel savings. Crops with less N demand, such as grasses and woody coppice species have more favourable climate impacts. This analysis only considers the conversion of biomass to 20 biofuel. It does not take into account the use of fossil fuel on the farms and for fertilizer and pesticide production, but it also neglects the production of useful co-products. Both factors partially compensate each other. This needs to be analyzed in a full life cycle assessment.
Pdf 全文链接：
http://www.atmos-chem-phys-discuss.net/7/11191/2007/acpd-7-11191-2007.pdf
