Carbon Budget and Cost Analysis of C2CNT: A Carbon Dioxide to Solid Carbon Conversion Process
Open AccessThe industrial sector accounts for approximately 30% of global CO2 emissions as of 2015 and lacks mature technologies to substantially reduce emissions. Many industrial processes, such as cement production, emit carbon dioxide (CO2) without a viable low carbon alternative. Carbon Dioxide Removal (CDR) technologies offer a means of mitigating industrial emissions.This dissertation considers the feasibility of a new electrochemically-based CDR technology currently under development called “Carbon dioxide to Carbon Nanotubes” (C2CNT), which is capable of converting CO2 emissions from industrial smokestacks into a range of high-value solid carbon materials (e.g., graphite, carbon fibers, and carbon nanotubes) which could be sold as manufacturing materials for a variety of applications. This feasibility assessment is comprised of two elements.Under the first research element the lifecycle carbon budget of a full scale model is assessed based on best available lab information. The research findings show electricity consumption is a key driver in the C2CNT carbon conversion process. By using a renewable or low-carbon source of electricity, the process can result in a 77-98% reduction in net CO2 emissions. It is estimated that C2CNT requires 2,436 kWh of electricity to convert one tonne of CO2 into CNT. A sensitivity analysis indicates that source and amount of electricity consumption are critical elements in net carbon emissions from the C2CNT process. The C2CNT process could substantially lower the price of carbon nanotubes making it a valuable substitute for construction materials. C2CNT Carbon would therefore result in avoided CO2 emissions from other construction materials such as steel, aluminum or titanium. The C2CNT process also produces pure O2, which could be injected into the combustion chamber of an industrial process allowing it to operate more efficiently and eliminate oxides of nitrogen which are potent greenhouse gases and contribute to ground level ozone.The carbon budget study demonstrates the C2CNT technology can substantially reduce greenhouse gas (GHG) emissions from industrial processes and could offer a revenue generating alternative compared to other Carbon Capture and Sequestration (CCS) technologies. Further research is needed to scale up the C2CNT technology to a large continuous-flow process.Under the second research element, an economic feasibility analysis is presented for C2CNT. The results estimate C2CNT operating costs are primarily driven by the 8.93 MWh of electricity/tonne of carbon, which at $80/MWh will cost $714/tonne of solid carbon. The calculations also assume a 5% loss of lithium carbonate molten salt during the process, which at $8,000/tonne will cost $400/tonne to replenish the lithium carbonate. Together, these result in a primary operating cost of $1,114/tonne. In comparison, a modern aluminum smelter which uses a similar electrochemical process has operating costs of $1,300-$2,000/tonne of aluminum. C2CNT uses 36-40% less electricity compared to an aluminum smelter. Assuming the capital costs of building a C2CNT facility is similar to an aluminum smelter ($3,500-$5,000/tonne of installed capacity), a C2CNT facility capable of processing 2 million tonnes of CO2/year (typical CO2 emissions from an average cement plant) would cost $1.9-$2.7 billion. The C2CNT facility processing 2 million tonnes of CO2 annually has the potential to generate $1.08 billion (at $2,000/tonne of CNT) to $5.4 billion (at $10,000/tonne of CNT) in revenue. This technology contrasts with other CDR technologies that often do not create a large revenue stream and create potential liabilities. Lastly, a sensitivity analysis indicates that a carbon nanotube price in the region of $3,000 is very likely to yield a positive Net Present Value (NPV) for a C2CNT plant and even prices below this have a high likelihood of a positive NPV. Thus C2CNT potentially represents an economically viable CDR technology that could play a major role in reducing greenhouse gas emissions from industrial processes.
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