Impact of Algal Harvesting Technology on Ecosystem Function

我们越来越依赖化石燃料作为能源，这给人类带来了多重问题。全球政治稳定受到化石燃料生产国的强烈影响，价格也随之变化。化石燃料的可获得性也是有限的，因此不可避免地需要替代能源。然而，对环境的有害影响可能是最严重的。不断上升的二氧化碳水平是气候变化的一个主要因素。生物燃料是一种来自可再生生物材料的替代能源。这种燃料来源的主要优势是碳中性，因为二氧化碳排放通过用于制造生物材料的二氧化碳固定来平衡。然而，最初对生产生物燃料的热情随之而来的是一种意想不到的但实质性的副作用。农业用地被用来种植生物燃料作物，而不是粮食作物，这加剧了粮食短缺问题。随着世界人口到2050年达到预计的92亿，粮食短缺情况预计将恶化[1]。因此，必须谨慎对待生物燃料生产对社会、经济和环境的影响。尽管这些问题高度相关，但可以说，转向可再生能源的主要驱动力仍然是经济的。利用藻类生产生物燃料的效率在过去几年里有了显著的提高，例如，通过基因工程增加了脂肪燃料的含量(2)，然而，仍然存在一些瓶颈，使其在经济上可行。一个主要问题是与捕捞藻类相关的能源成本，其中高达30%的成本可能来自(3)。在谢菲尔德大学，一种多次获奖的设备可以用最少的能量投入来收获细胞，因此有能力使生物燃料生产在经济上比化石燃料更具竞争力(4)。现有技术已被证明是侵入性的，并存在规模扩大的问题。该设备使用层流来产生气泡通量，并已被证明在收获方面有99.2%的效率(3)。这项技术可以用于单一养殖的藻类池塘和天然湖泊生态系统，尽管这一过程对环境的影响尚未得到测试。随着粮食需求的增加，饮用水需求也随之增加，特别是在中国和印度这样的快速发展国家(5)。饮用水湖泊的富营养化已使人们对严重缺水的担忧成为现实(6)，这一环境问题在世界范围内普遍存在(7)。该微浮选装置具有修复藻类湖泊并恢复用于后续饮用水处理的能力。中国提出了将收获的藻类用于生物燃料生产的目标，以抵消所需的能源投入。在这个项目中，将使用人工湖生态系统在微观层面评估这项技术的环境影响。从湖泊中清除藻类和细菌有可能改变生态系统的结构和功能，并对食物网产生影响。微生物在化学和营养循环中扮演着重要的角色，因此它很可能会被收获过程改变。在这个项目中，收获强度将是不同的，变化将被量化，监测和建模，使用定量的代谢蛋白质组学方法。这种方法特别着眼于蛋白质的产生，这是至关重要的，因为蛋白质是细胞中的功能实体。使用这些数据的新陈代谢模型将与食物网结构的生态模型相结合。总体目标是能够控制用于生物燃料的连续藻类养殖或使用后续一代生物燃料的水修复的生态系统稳定性。1.Levy，M.等人。2005.2。拉达科维茨等人，20103。哈诺图，J.等人，20114。齐默尔曼，WB.20115。吴超，20116。Gao，C.等人。20107。道兹，W.K.，等人，2009

Our ever increasing reliance on fossil fuels as an energy source is causing mankind multiple problems. Global political stability is strongly influenced by fossil fuel producing countries and prices vary accordingly. Fossil fuel availability is also finite and therefore alternatives will inevitably be required. However, the detrimental impact on the environment is perhaps the most significant. Rising CO2 levels are a major contributor to climate change. Biofuels are an alternative source of energy derived from renewable biological material. The major advantage of this fuel source is the carbon neutrality because CO2 emission is balanced by the CO2 fixation used to make the biological material. However, the initial wave of enthusiasm for producing biofuels was met by an unpredicted but substantial side effect. Agricultural land was being used for biofuel crops instead of food crops and compounding the food shortage problem. Food deficiency is expected to worsen as the world's population reaches the predicted 9.2 billion by 2050 (1). Therefore, caution in terms of the social, economic and environmental impacts of biofuel production must be taken. Although these issues are highly relevant, it can be argued that the main driver for moving towards renewable energy sources remains economical. The efficiency of biofuel production from algae has improved dramatically in the last few years, for example, increased lipid fuel content through genetic engineering (2), however, several bottlenecks remain to make it economically viable. One major issue is the energy cost associated with harvesting algae, where up to 30% of costs can originate (3). At the University of Sheffield, a multi-award winning device can be used to harvest cells using minimum energy input and therefore has the ability to make biofuel production more economically competitive with fossil fuels (4). Existing techniques have been shown to be intrusive and have scale-up issues. The device uses laminar flow to create a bubble flux and has been shown to be 99.2% efficient in harvesting (3). The technology can be used in monoculture algal ponds and natural lake ecosystems, although the environmental impact of process has not been tested. With increasing food demand comes the increase in drinking water demand, especially in rapidly developing countries like China and India (5). Eutrophication of drinking water lakes has caused fears of major water shortages to become a reality (6), and this environmental problem is prevalent worldwide (7). The microflotation device has the ability to remediate the lake of algae and restore for subsequent drinking water treatment. The aim of using the harvested algae for biofuel production has been proposed in China to offset the energy input required. In this project, environmental impact of this technology will be assessed at the microcosm level using an artificial lake ecosystem. The removal of algae and bacteria from the lake has the potential to alter ecosystem structure and function and impact on food webs. Microbes play an essential role in chemical and nutrient cycling and therefore it is likely to be altered by the harvesting process. In this project, the harvesting intensity will be varied and the changes will be quantified, monitored and modelled, using a quantitative metaproteomic approach. This method specifically looks at protein production which is crucial as proteins are the functional entities in cells. Metabolic modelling using this data will be combined with ecological modelling of food web structure. The overall objective is to be able to control ecosystem stability for either continuous algal farming for biofuel, or water remediation with subsequent generation of biofuels. 1. Levy, M., et al. 2005.2. Radakovits, R., et al., 20103. Hanotu, J., et al., 20114. Zimmerman, WB. 20115. Wu, C., 20116. Gao, C., et al. 20107. Dodds, W. K., et al., 2009