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Introduction to the Special Section on Carbon Dioxide

Carbon dioxide is widely known as one of the primary greenhouse gases leading toward global climate change. The National Oceanic and Atmospheric Administration reports that global average CO2 concentration was 405 ppm in 2017, the highest concentration recorded in over 800,000 years. As chemical engineers, we are actively engaged in understanding the relationship between energy generation and atmospheric CO2 and seeking new ways to generate energy that do not produce CO2. In addition to developing these new alternative energy technologies, we are also engaged in removing CO2 from the effluent stream, thereby reducing the impact of burning fossil fuels or “capturing” carbon when biofuels are consumed. Likewise, engineers are actively working on technologies that can remove CO2 from the atmosphere. Once the CO2 is obtained, it is important that it be utilized or stored so that it is not returned to the atmosphere or not added to the growing carbon stock already present. Sequestration techniques require the capture and storage of CO2, which means better understanding of the adsorption processes and the development of new sorbents that can achieve higher capture rates. Beyond that, CO2 can be used as a raw material from which chemicals can be produced, reducing the consumption of new fossil resources while simultaneously taking this greenhouse gas from the atmosphere. This issue was developed in part to expand on the current global conversation around climate change and the impact of emissions from fossil fuel combustion. The recent actions taken during COP 24 in Poland, although not as substantial as most would have liked, demonstrate the global objective to place limits on our carbon emissions, and scientists across the world are seeking new technical solutions that can guide policymakers on viable choices. Several of the manuscripts included in this special section can speak directly to those needs and opportunities. The current issue includes a compilation of recent submissions to Environmental Progress & Sustainable Energy that investigates many facets of the CO2 challenge. In addition to the concerns expressed through the classical discussion of carbon capture, utilization, and storage (CCUS), we evaluate both the relationship between carbon emissions and climate change and the use of policy to modify industrial behavior, as well as the impacts of bioenergy and other sources from a life cycle approach. The special section begins with a review article describing the driving forces for climate change, and in particular looks at opportunities for mitigation. The following five contributions provide further description of the use of policy to modify behavior and the relationship between carbon emissions and economic growth. These papers provide an excellent discussion on the relationship, or more precisely, the lack of correlation between economic benefit and carbon emissions, leading to recognition that the development of smart restriction on emissions will not necessarily impact the economic success of either a business or the nation, and by extension, provides a roadmap for environmentally friendly economic prosperity. In the next six contributions, authors address the issues of CCUS. In the first of these papers, the development of new sorbent materials and the analysis of their performance for CO2 capture are described. Following is a series of papers that consider new ways in which CO2 can be converted to chemicals or fuels through catalytic means. Thermodynamic analysis describes the preferred conditions under which CO2 can potentially be converted to desired products, taking this resource from the atmosphere and making it a viable feedstock. Finally, one contribution discusses CO2 storage in biological systems, which has the added advantage of providing a viable pathway for the production of useful products. The last section comprises five contributions that describe alternatives to traditional fossil fuel combustion and explores life cycle issues associated with these energy resources. Ranging from a discussion of energy diversification to a detailed analysis of two alternative energy strategies, this section considers a variety of options that can be explored as we transition to a low carbon future. Overall, this special section encompasses much of the current thinking related to the reduction of carbon emissions, the utilization of CO2 that can ameliorate its presence and provide useful products, and storage options. The discussions around the relationship between CO2 emissions, alternate energy choices, and economic growth suggest a path forward that should be of interest to all readers, but should be especially useful in working to develop long-term strategies in keeping with the suggestions of the COP 24 outcomes. Although not a comprehensive review, this special section provides a valuable starting point for those needing to better understand the current state of the art. Thank you for reading.