Evaluation of strategies for the subsequent use of CO2

If substantial amounts of CO2, which according to actual scenarios may in the future be captured from industrial processes and power generation, shall be utilized effectively, scalable energy efficient technologies will be required. Thus, a survey was performed to assess a large variety of applications utilizing CO2 chemically (e.g., production of synthesis-gas, methanol synthesis), biologically (e.g., CO2 as fertilizer in green houses, production of algae), or physically (enhancement of fossil fuel recovery, use as refrigerant). For each of the processes, material and energy balances were set up. Starting with pure CO2 at standard conditions, expenditure for transport and further process specific treatment were included. Based on these calculations, the avoidance of greenhouse gas emissions by applying the discussed technologies was evaluated. Based on the currently available technologies, applications for enhanced fossil fuel recovery turn out to be most attractive regarding the potential of utilizing large quantities of CO2 (total capacity > 1000 Gt CO2) and producing significant amounts of marketable products on one hand and having good energy and material balances on the other hand \( \left( {{{t_{CO_2 - emitted} } \mathord{\left/ {\vphantom {{t_{CO_2 - emitted} } {t_{CO_2 - utilized} 0.34}}} \right. \kern-\nulldelimiterspace} {t_{CO_2 - utilized} > 0.34}} \)). Biological processes such as CO2 fixation using micro-algae look attractive as long as energy and CO2 balance are considered. However, the development of effective photo-bioreactors for growing algae with low requirements for footprint area is a challenge.