CO2 utilization: Turning greenhouse gas into fuels and valuable products

This study critically reviews the recent developments and future opportunities pertinent to the conversion of CO₂ as a potent greenhouse gas (GHG) to fuels and valuable products. CO₂ emissions have reached an alarming level of around 410 ppm and have become the primary driver of global warming and climate change leading to devastating events such as droughts, hurricanes, torrential rains, floods, tornados and wildfires across the world. These events are responsible for thousands of deaths and have adversely affected the economic development of many countries, loss of billions of dollars, across the globe. One of the promising choices to tackle this issue is carbon sequestration by pre- and post-combustion processes and oxyfuel combustion. The captured CO₂ can be converted into fuels and valuable products, including methanol, dimethyl ether (DME), and methane (CH₄). The efficient use of the sequestered CO₂ for the desalinization might be critical in overcoming water scarcity and energy issues in developing countries. Using the sequestered CO₂ to produce algae in combination with wastewater, and producing biofuels is among the promising strategies. Many methods, like direct combustion, fermentation, transesterification, pyrolysis, anaerobic digestion (AD), and gasification, can be used for the conversion of algae into biofuel. Direct air capturing (DAC) is another productive technique for absorbing CO₂ from the atmosphere and converting it into various useful energy resources like CH₄. These methods can effectively tackle the issues of climate change, water security, and energy crises. However, future research is required to make these conversion methods cost-effective and commercially applicable.

CO2 capture and storage: A way forward for sustainable environment

The quest for a sustainable environment and combating global warming, carbon capture, and storage (CCS) has become the primary resort. A complete shift from non-renewable resources to renewable resources is currently impossible due to its major share in energy generation; making CCS an imperative need of the time. This study, therefore, aims to examine the reckoning of carbon dioxide (CO₂), measurement methods, and its efficient capture and storage technologies with an ambition to combat global warming and achieve environmental sustainability. Conventionally, physical, geological and biological proxies are used to measure CO₂. The recent methods for CO₂ analyses are spectrometry, electrochemical gas sensors, and gas chromatography. Various procedures such as pre, post, and oxyfuel combustion, and use of algae, biochar, and charcoal are the promising ways for CO₂ sequestration. However, the efficient implementation of CCS lies in the application of nanotechnology that, in the future, could provide a better condition for the environment and economic outlooks. The captured carbon can be stored in the earth crust for trillions of years, but its leakage during storage can raise many issues including its emissions in the atmosphere and soil acidification. Therefore, global and collective efforts are required to explore, optimize and implement new techniques for CCS to achieve high environmental sustainability and combat the issues of global warming.