Policy Analysis

Policy Analysis(政策分析) Life-Cycle Assessment of BiodieselProduction from Microalgae

生命周期评估的生物柴油生产藻类 L A U R E N T L A R D O N , * , † A R N A U D H ´E L I A S , † , ‡BRUNO S I A L V E , • J E A N - P H I L I P P E S T E Y E R , †AND O L I V I E R BERNARD• INRA, UR50 Laboratoire de Biotechnologie del’Environnement, Avenue des Etangs,11100 Narbonne, France, Montpellier SupAgro, 2 Place PierreViala, 34060 Montpellier Cedex 1, France, and Comore, INRIA,BP93, Sophia-Antipolis Cedex 06902, France Received March 10, 2009. Revised manuscript receivedJune 8, 2009. Accepted June 18, 2009. LAURENTLARDON，* ELIAS†ARNAUDH'，†，‡BRUNO SIALVE§JEAN - PHILIPPESTEYER，†和Olivier陈智思§ INRA，UR50实验室Biotechnologie DE L'环境，AVENUE DES Etangs酒店，11100纳博讷，法国，蒙彼利埃SupAgro，2地点皮埃尔维亚拉，34060 Cedex的蒙彼利埃，法国，科摩罗，INRIA，BP93，索菲亚 - 安提波利斯06902 Cedex的法国 收稿日期：2009年3月10日，修改稿接受日期：2009年6月8日，认证日期：2009年六月18日

This paper provides an analysis of the potential environmentalimpacts of biodiesel production from microalgae. Highproduction yields of microalgae have called forth interest ofeconomic and scientific actors but it is still unclear whether theproduction of biodiesel is environmentally interesting andwhich transformation steps need further adjustment andoptimization. A comparative LCA study of a virtual facility hasbeenundertaken to assess the energetic balanceandthe potentialenvironmental impacts of the whole process chain, from thebiomass production to the biodiesel combustion. Two differentculture conditions, nominal fertilizing or nitrogen starvation,as well as two different extraction options, dry or wet extraction,have been tested. The best scenario has been compared tofirst generation biodiesel and oil diesel. The outcome confirmsthe potential of microalgae as an energy source but highlightsthe imperative necessity of decreasing the energy and fertilizerconsumption. Therefore control of nitrogen stress during theculture and optimization of wet extraction seem to be valuableoptions. This study also emphasizes the potential of anaerobicdigestion of oilcakes as a way to reduce external energydemand and to recycle a part of the mineral fertilizers 本文提供从微藻生产生物柴油的潜在环境影响的分析。微藻产量高，提出了所谓的经济界和科学界的兴趣，但目前还不清楚是否环保有趣的生物柴油的生产和转换步骤需要进一步调整和优化。虚拟设施比较LCA研究已开展评估的整个过程链的能量平衡和对环境的潜在影响，从生物质生产生物柴油燃烧。两种不同的培养条件下，名义施肥或氮饥饿，以及两种不同的提取选项，干法或湿法提取，已通过测试。最好的情况已经比第一代生物柴油和石油柴油。该结果证实微藻的电势作为能量来源，但突出的需要，降低能源和肥料消费。因此，文化和优化湿法提取过程中控制氮胁迫似乎是有价值的选择。这项研究还强调，作为一种方式，以减少外部能量的潜力厌氧消化油饼需求和回收的矿物肥料的一部分. 1. Introduction(介绍) During the past ten years, fossil fuel depletion and globalwarming issues have strongly motivated research on fuelproduction from biomass. Biofuels based on vegetal oil orbioethanol have the key advantage of relying on existingdistribution networks and current engine technology. Incomparison to oil fuel, biofuel can represent an improvementin terms of emissions of fossil CO2; however, such atechnology can also induce negative environmental impacts,caused for instance by pesticides and fertilizers, and canalso create a competition for land use with food crops. Therefore the use of first generation biofuel as a sustainablealternative to fossil fuels is questionable and has been thesubject of controversy (1). On the other hand, microalgaeseem to be an attractive way to produce biofuel due to theirability to accumulate lipids and their very high actual photosynthetic yields; about 3-8% of solar energy can beconverted to biomass whereas observed yields for terrestrialplants are about 0.5% (2, 3). These interesting propertieslead to potential productivities (in terms of oil productionper ha and per year) which are far higher than those ofrapeseed or sunflower (4). This high productivity combinedwith both the moderate competition with feed crop and thepossibility to uptake industrial sources ofCO2 has motivatedstudies depicting microalgae as an alternative source ofvegetal oil for biodiesel (2, 4). Despite strong interest from economic and scientificactors, up to now, there is to our knowledge no industrialfacility producing biodiesel from microalgae. The studiesundertaken on the subject have been restricted to lab andpilot scales. Hence, no thorough Life Cycle Assessment ofthe production chain from microalgae culture to biodieselis currently available, with the exception of LCA studies aboutthe cofiring of microalgae with coal (5). The aim of this studyis therefore to assess the environmental impacts of thistechnologically immature process. To do so, we extrapolatedlaboratory observations combined with known processesdeveloped for first generation biofuel to design a realisticindustrial facility. The potential pollution transfers arecomputed for various scenarios and guide the choice ofselected steps in the process chain. In addition to the overallenergetic balance of the production chain, the impacts ofthe combustion of algal biodiesel are compared to thoseproduced by first generation biofuel and diesel fuel. Theconsidered functional unit of the LCA is the combustion of1 MJ of fuel in a diesel engine; the boundaries includeextraction and production of raw materials, facility constructionand dismantling, biofuel elaboration, and use inthe engine. It is a “from cradle to combustion” analysis forthe fuel and a “from cradle to grave” analysis for the facility.The key objective of this study is not to offer a LCA of thecurrent microalgal biodiesel technology, but to identify theobstacles and limitations which should receive specificresearch efforts to make this process environmentallysustainable. 在过去的十年中，化石燃料枯竭和全球变暖问题有强烈动机的推动研究从生物质生产燃料。生物燃料的植物油或生物乙醇的基础上依托现有的分销网络和当前的引擎技术的关键优势。石油燃料相比，生物燃料可以代表化石二氧化碳的排放量方面的改进，然而，这样的技术也可以引起对环境的负面影响，例如引起农药和肥料，还可以创建一个与食物的土地使用竞争农作物的环境。 因此，作为一个可持续发展的第一代生物燃料替代化石燃料的使用是值得商榷的，并一直受到争议（1）。另一方面，微藻似乎是一个有吸引力的方式来生产生物燃料，由于积累脂质和非常高的实际光合产量的能力;太阳能的3-8％左右，可以转换为生物量，而观察到的陆