Seth Jyoti R, Wangikar Pramod P
Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, India.
DBT-Pan IIT Center for Bioenergy, Indian Institute of Technology Bombay, Powai, Mumbai, India.
Biotechnol Bioeng. 2015 Jul;112(7):1281-96. doi: 10.1002/bit.25619. Epub 2015 May 15.
Aquacultures of microalgae are frontrunners for photosynthetic capture of CO2 from flue gases. Expedient implementation mandates coupling of microalgal CO2 capture with synthesis of fuels and organic products, so as to derive value from biomass. An integrated biorefinery complex houses a biomass growth and harvesting area and a refining zone for conversion to product(s) and separation to desired purity levels. As growth and downstream options require energy and incur loss of carbon, put together, the loop must be energy positive, carbon negative, or add substantial value. Feasibility studies can, thus, aid the choice from among the rapidly evolving technological options, many of which are still in the early phases of development. We summarize basic engineering calculations for the key steps of a biorefining loop where flue gases from a thermal power station are captured using microalgal biomass along with subsequent options for conversion to fuel or value added products. An assimilation of findings from recent laboratory and pilot-scale experiments and life cycle analysis (LCA) studies is presented as carbon and energy yields for growth and harvesting of microalgal biomass and downstream options. Of the biorefining options, conversion to the widely studied biofuel, ethanol, and manufacture of the platform chemical, succinic acid are presented. Both processes yield specific products and do not demand high-energy input but entail 60-70% carbon loss through fermentative respiration. Thermochemical conversions, on the other hand, have smaller carbon and energy losses but yield a mixture of products.
微藻养殖是从烟道气中光合捕获二氧化碳的领跑者。便捷的实施要求将微藻二氧化碳捕获与燃料和有机产品的合成相结合，以便从生物质中获取价值。一个综合生物精炼厂包括一个生物质生长和收获区以及一个用于转化为产品并分离至所需纯度水平的精炼区。由于生长和下游操作需要能量并导致碳损失，总体而言，该循环必须是能源正向、碳负向的，或者能带来可观的附加值。因此，可行性研究有助于从快速发展的技术选项中做出选择，其中许多仍处于开发的早期阶段。我们总结了生物精炼循环关键步骤的基本工程计算，在该循环中，利用微藻生物质捕获来自火力发电站的烟道气，以及随后转化为燃料或增值产品的选项。本文展示了近期实验室和中试规模实验以及生命周期分析（LCA）研究结果的综合，即微藻生物质生长和收获以及下游选项的碳和能量产量。在生物精炼选项中，介绍了转化为广泛研究的生物燃料乙醇以及制造平台化学品琥珀酸的过程。这两个过程都能产生特定产品，且不需要高能量输入，但通过发酵呼吸会导致60 - 70%的碳损失。另一方面，热化学转化的碳和能量损失较小，但会产生混合产品。
