Rapid urbanization and dramatic increase in industrialisation leads to heavy carbon dioxide (CO₂) emissions in atmosphere. These emissions generally arise from two broad sources: natural processes namely, decomposition, ocean release and respiration; and human sources like burning fossil fuels, solid waste, wood products, deforestation and cement production, etc. Increase in carbon dioxide level in environment contributes to rise in temperature leading to global warming, which in turn causes severe climate change. So, it is highly essential to reduce the amount of CO₂in atmosphere.

Naturally, carbon dioxide is removed from the atmosphere by plants as a part of the biological carbon cycle. Another aspect to reduce CO₂emissions is largely by adopting renewable resources instead of fossil fuels. Recently, some technically innovative ideas have been implemented to devise a technology to shift CO₂, the most abundant anthropogenic gas, from a climate change problem to a valuable commodity. Among various approaches, “Diamond from sky” is a novel method developed by Stuart Licht and group from Washington University which claims to convert atmospheric CO₂ directly into highly valued carbon nanofibers for industrial and consumer products. Carbon fibre is a demanding material used to make strong carbon composites for high-end sports equipment, wind turbine blades and other products.

The term diamond is used here in the context of precious material like carbon nanofibers that can be made economically from atmospheric carbon and oxygen.  It is a low energy process that requires only few volts of electricity, sunlight and CO₂. The method briefly includes breaking down of carbon dioxide molecules in an electrolytic bath of molten carbonates kept at high temperature (750^oC). In the presence of heat and electricity, CO₂ gets dissolved and carbon nanofibers are formed at steel/nickel electrode.This process is known as electrolytic syntheses method.The required heat and electricity for process is produced by using hybrid concentrating solar energy systems (solar cells and solar thermal). The estimated cost for solar thermal system is around $1000 per ton of carbon nanofiber produced, which is 100 times less than value of product. With a physical area of less than 10 % the size of Sahara Desert, the amount of CO₂ removal can take the atmosphere to pre-industrializationera within 10 years of span.

In another similar approach, Dutch artist Daan Roosegaarde came up with a tower that sucks up the smog and turns into clean air. The filtered-out smog particles are turned into diamonds (gem stones). The tower has been used in Rotterdam, Beijing, Tianjin and Dalian that sucks upto 30,000 cubic meters of polluted air, cleans it at nano level (PM 2.5, PM 10 particles) and then releases it back into the city. The tower is powered by solar energy and gives around 50-75 % cleaner air than rest of city. The smog particles are filtered by tower are compressed for 30 minutes and turned into dark gemstones. Such technologies unveil promising ways of handling the CO₂ emissions while purifying the polluted air; however, extensive efforts are required to establish such facilities all over the world.

Author: Dr Alka Pareek, National Post Doc, Bioengineering and Environmental Science Lab, EEFF Department, CSIR-Indian Institute of Chemical Technology.