LCA of biodiesel production from micro-algae coupled to Anaerobic Digestion of oilcakes. Lardon, L., Hélias, A., Sialve, B., Bernard, O., & Steyer, J. In Life Cycle Management Conference LCM, pages poster, 2009.
LCA of biodiesel production from micro-algae coupled to Anaerobic Digestion of oilcakes [pdf]Paper  abstract   bibtex   
Fossil fuel depletion and climate change have lead many research groups and private companies to focus on use of biomass to produce renewable energy and fuel. Production and use of bioethanol and biodiesel have usually a lower global warming potential than petrodiesel but they create other environmental impacts and compete with feed crop for the land use. Micro-algae have been pointed as an interesting alternative: their very high photosynthetic yield allows one to obtain high biomass production spread over the whole year and their ability to accumulate lipid lead to potential productivities (in terms of oil production per year and per hectare) far higher than rape seed or sunflower. The lipid fraction can be converted to biodiesel by trans-esterification after proper harvesting and extraction. Moreover thanks to the semi-controlled culture systems, micro-algae culture can be used to use an industrial source of CO2 like cement factory or power plant fumes. A virtual facility has been designed from reasonable assumptions in agreement with bibliographic data and observations of comparable processes. It was then used to carry out a Life Cycle Assessment of the whole process chain, from the biomass production to the biodiesel combustion, including infrastructure building and recycling. Potential environmental impacts have been assessed with the CML method, and energetic balance determined with the Cumulative Energy Demand method. Potential impacts have been compared to the ones obtained in former studies for first generation biodiesel and petro-diesel. First analysis highlights the imperative necessity to decrease the energy consumption during cultivation and drying of micro-algae. It stresses the importance of extracting energy and nutrients from oilcakes and finally it shows the relevance of applying nitrogen-stress during algae culture. Anaerobic digestion has often been proposed as a relevant coupled process to recycle part of the nutrients stored in the oilcakes; in addition produced biogas can be used to produce heat and electricity on the facility. The former system has been modified and coupled to anaerobic digestion of oilcakes in order to evaluate potential of anaerobic digestion of oilcakes to reduce environmental impacts and improve energetic balance. Oilcakes are processed with another biomass to facilitate its anaerobic digestion by increasing the C/N ratio. This second assessment shows a far better environmental footprint of bioenergy production from micro-algae cultivation when coupled to anaerobic digestion. It should reduce most of the most impacting steps of the production chain, reducing the use of energy and fertilizers. However drying remains a critical step for which alternative options should be experimentally evaluated.

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