The ins and outs of carbon dioxide.

In many ways, carbon dioxide has been mischaracterized because of its association with greenhouses and global warming. But in fact, carbon dioxide is a naturally occurring gas with many useful functions. From carbonated drinks, to fire extinguishers, to inflatable life jackets, carbon dioxide has a number of useful rolls in our modern world. But more importantly, carbon dioxide is essential for life on our planet, because it is required for the photosynthesis that plants utilize to convert energy into the food we eat.

While carbon dioxide is not a poison, it can be dangerous in high concentrations or enclosed environments where it displaces oxygen. But in the open air, carbon dioxide dissipates quickly, making it an unlikely risk to public health.

One main concern with carbon dioxide is its role in global warming and the rate at which it is increasing in the atmosphere. From arctic ice core samples, it is estimated that carbon dioxide levels have remained largely stable for thousands of years, ranging from 260 to 280 parts per million. Since the dawn of the industrial revolution, however, carbon dioxide levels have increased by 36%, with half of that increase occurring since 1973. Carbon dioxide concentrations have increased from 280 parts per million (ppm) prior to mid-1700s to around 370 ppm today. It is this rapid acceleration that has the primary source of concern for researchers studying global climate change and its related effects.

Where on Earth does CO2 come from?
Carbon dioxide emissions can be produced through natural and human activities. The rapid increase in atmospheric carbon dioxide has led many to focus on industrial sources of CO2 — that is the carbon released into the air when fossil fuels are burned. However, natural sources of carbon dioxide such as animal and plant respiration, volcanic eruptions, and thawing permafrost also contribute to CO2 concentrations in the atmosphere.

Of sinks and sources.
During the natural carbon cycle, carbon is released into the atmosphere from various sources and absorbed through "sinks." For example humans and plants give off carbon dioxide through respiration, making them a source of carbon dioxide, while plants absorb carbon dioxide during photosynthesis, making them a sink. The ocean acts both as a source and a sink, releasing carbon dioxide and absorbing it through natural processes. Volcanic eruptions act as a natural source of CO2. However, the amount of carbon released through volcanic eruptions is relatively small.

Human contributions.
While a certain amount of the carbon dioxide in our atmosphere is created through natural processes like respiration, wildfires, and volcanic activity, human activity is a the largest source of global CO2 emissions. This is primarily because so much of our modern life requires power generated by burning fossil fuels, such as coal used for electricity and oil used for transportation. Fossil fuels are created when ancient plant and animal material is buried, transformed, and preserved in sediments over a long period of time (millions of years). As these fuels are recovered and burned, the carbon within them is released, combining with the oxygen in the air to create carbon dioxide. Below are some of the main sources of human-generated carbon dioxide.

Power generation
From lights and air conditioning to the power for our computers and TVs, power generation consumes much of the world's energy resources. Much of the electricity we use is produced through the use of fossil fuels like coal, making power generation one of the largest sources of manmade carbon emissions.

After power generation, transportation is the second largest contributor to global carbon emissions. Petroleum is the main fossil fuel consumed in this activity, providing the fuel that drives our personal vehicles, trains, planes, and most shipping around the world.

Industrial production
Pretty much everything we eat, use or consume involves factory production at some point. This requires the extensive use of fossil fuels in plants around the globe. At one point, much of this activity was focused in the United States. But as China and other countries increase their industrial output, much of the carbon dioxide released through industrial production has shifted to Asia.

Residential use
In addition to the power demand for lights and appliances, many homes and commercial properties use fossil fuels like natural gas for much of their space and water heating needs.

In addition to traditional manufacturing, there are a number or specialized industrial production processes and product uses that result in the release of CO2. Mineral production, metal refining and the development of petroleum-based products like plastic all result in carbon dioxide emissions. Carbon dioxide is also released in the production of the cement used in concrete and mortar incorporated heavily in most construction projects.

Mankind's role in increasing carbon dioxide levels is not only measured in the things that we make but also the things we destroy. Because the plant life in forests provide a natural sink that offsets large amounts of carbon dioxide production, increasing deforestation is also considered a factor in global climate change.

Midwest Geological Sequestration Consortium
Midwest Geological Sequestration Consortium
Advanced Energy
Technology Initiative

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