Reduction of co₂ to chemicals and fuels: a solution to global warming and energy crisis

Abstract

We are living in an era of unprecedented technological innovation, progress, and prosperity driven by energy. The industrial revolution, since the 1860s, and the exponential urbanization during last 2 decades caused a dramatic increase in carbonaceous emissions into the atmosphere, which contributed to most of the unprecedented global warming over the past decade. Smog hanging over cities is the most familiar and apparent form of air pollution that has become a regular phenomenon. However, a more serious and harmful form of air pollution occurs through enormous anthropogenic (or industrial) emission of carbon dioxide (CO₂), a nonvisible greenhouse gas. Over millions of years, plants used to assimilate CO₂ into energy-rich compounds (carbohydrates) by a process called photosynthesis, through which nature used to maintain its own carbon cycle to present us a sustainable environment. Unfortunately, the industrial revolution and modern civilization during the last few centuries necessitated the use of excess fossilized sunlight (fossil fuels) accumulated over millions of years. Consequently, the CO₂ that was stored as carbohydrates by photosynthesis over millions of years is being returned back to the atmosphere at an incredibly alarming rate. These activities have substantially impacted the natural carbon cycle, which is no longer sufficient to maintain the carbon balance over the various sectors of the environment. The CO₂ concentration in Earth’s atmosphere is rising drastically more than ever in the Earth’s history, and this phenomenon is expected to have major impacts on the Earth’s climate and human civilization as well. Thus, it is correctly envisioned that the oil age will end much before the Earth actually runs out of oil, being restricted by emission regulations of fossil fuel usage. There are various sources of CO₂ emissions that can generally be classified as stationary, mobile, and natural sources, as listed in Table 1. (1−3) Among them, power generation and manufacturing sectors contribute the majority of the CO₂ emissions to the environment. The flue gas stream from coal and natural gas power generation basically consists of various gases including nitrogen, CO₂, water vapor, oxygen, soot, CO, nitrogen oxides, and sulfur oxide. In the past 150 years, such activities have pumped enough CO₂ into the atmosphere to push the atmospheric CO₂ level beyond the deadly 400 ppm mark. There are no standard technologies developed to efficiently convert CO₂ from these streams due to the presence of water vapor and all pollutants, which is likely to decompose/poison most of the catalysts and decrease the efficiency of the conversion of CO₂.