Impact of Algal Harvesting Technology on Ecosystem Function

点击翻译按钮获取中文摘要

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