A team of researchers at George Washington University led by Prof. Stuart Licht reports that the addition of carbon nanotubes (CNTs) produced from CO2 by low-energy C2CNT (CO2 to CNT) molten electrolysis (earlier post) to materials such as concrete or steel not only forms composites with significantly better properties, but amplifies the reduction of CO2. Their paper is published in the journal Materials Today Sustainability.
Massive carbon dioxide avoidance by the addition of carbon nanotubes synthesized from CO2 to CNT-composites. (A) Carbon mitigation with CNT-cement. (B) Carbon mitigation with CNT-Al. The latter (B) includes a cascade effect due to virgin Al’s large carbon footprint, triggering larger CNT-composite induced CO2 emission elimination. In the figure "ton" refers to metric tonne and CNT, carbon nanotube. Licht et al.
The focus of their study was the theoretical calculations of greenhouse gas CO2 reductions using CNT composite structural materials when formed with CNTs made from CO2, rather than conventional high-CO2-emissive production techniques such as CVD.
The C2CNT production is achieved at a fraction of the current cost of manufacturing nanotubes and results in a cost of carbon savings in the materials production significantly below the current cost of carbon mitigation. Furthermore, the removed CO2 is permanently stored, unlike, other methods like the production of fuels or seltzer water that re-release CO2 when the product is used.
In this discovery of the C2CNT-composite process, carbon nanotubes are produced by electrolysis at low cost consuming, rather than releasing, CO2, and then mixed with the structural material. Approximately 4 tonnes of CO2 is absorbed in this process for every tonne of carbon nanotubes produced.
This then avoids several hundred tonnes of CO2 by replacing structural materials with CNT composites. For example, a 2-tonne cement block with 0.001 tonne of CNTs has the same strength as a 3-tonne block without CNTs.
The 1-tonne cement avoided eliminates its CO2 production emission. Specifically, a 0.048 wt% CNT-cement composite eliminates 840 tonne of CO2/tonne CNT. CO2 is thus eliminated from the anthropogenic carbon cycle at less than $1 per tonne.
High carbon footprint materials such as aluminum trigger larger CO2 composite elimination effects. One ton of CNT can avoid:
- 4400 tons of CO2 in aluminum production,
- 2750 tons of CO2 in titanium production,
- 1800 tons of CO2 in magnesium production, or
- 300 tons of CO2 steel production.
The new C2CNT-composite process would allow, for example, the entire greenhouse gas emission of a fossil fuel power plant to be offset with a small, onsite C2CNT plant producing carbon nanotubes.
S. Licht, X. Liu, G. Licht, X. Wang, A. Swesi, D. Chan (2019) “Amplified CO2 reduction of greenhouse gas emissions with C2CNT carbon nanotube composites,” Materials Today Sustainability, doi: 10.1016/j.mtsust.2019.100023.