Fossil Fuels and Carbon Dioxide Management: Scientific and Social Challenges

Andy Wolfsberg
 

In 2006, there were 250 million registered passenger vehicles in the United States. They traveled 3 trillion miles and burned almost 200 billion gallons of gasoline. That’s a lot of zeros on some very large numbers and we can’t really fathom what it means. But, it surely means our appetite for transportation fuel is large. Our oil companies and law makers talk about how many millions of barrels of fuel PER DAY we need to produce… and how many millions more we need to import. We currently import about two-thirds of the crude oil necessary to satisfy our daily consumption, and most of that comes from geopolitically unstable regions -- parts of the world where it’s not so easy to assess who our friends really are.
 
Burning fossil fuels – oil, gas, and coal - creates carbon dioxide (CO2) emissions to the atmosphere. CO2 is a greenhouse gas, meaning it absorbs and emits radiation within the thermal infrared range. Greenhouse gases are essential to maintaining the current temperature of the Earth; without them this planet would be so cold as to be uninhabitable. But, by changing the concentration of greenhouse gasses in our atmosphere, do we impact a natural balance and cause climate change and global warming?
 
About half of the man-made CO2 emissions to the atmosphere in the United States come from burning oil products like gasoline. Another third comes from burning coal and the remainder comes from natural gas. So, we can basically say that half the CO2 we emit comes from driving cars and half from turning on our lights. And boy do we like to do both of those. The United States tops the list of CO2 emissions per person and accounts for one fifth of the entire world’s CO2 emissions. Per person, we emit more than twice as much CO2 as our European friends and almost five times as much as the Chinese. With their huge population, China accounts for a fifth of the entire world’s CO2 emissions and their fraction is growing. They want all of the comforts and luxuries that we have become accustomed to.
 
So, here’s the picture. In the US, we are producing a lot of CO2. It comes from burning fossil fuels to light our houses, power our economy, move us around – often in vehicles with a lot of empty seats, and most of our transportation fuel is imported. To top it off, we have huge resources of fossil energy here in the United States in the form of coal and oil-shales and we know how to turn them into transportation fuel. The only downside is that the process to do so is currently expensive and produces even more CO2. So, until our economy makes a huge change and we start driving electric cars charged by wind, solar, and nuclear energy, we have the fossil energy resources to keep doing just what we are doing. But, many believe we need to figure out what to do with the CO2. In fact, new laws regulate the emissions of CO2 from new fuel sources and proposed laws may regulate the emission of CO2 from power plants or place a limit on the CO2 footprint associated with industrial processes. Thus, figuring out what to do with CO2 instead of pumping it into the atmosphere has become a hot topic.
 
This is where the fun science comes in.
 
Several options for managing CO2 involve capturing it and storing it. By reacting it with other minerals, we could store it as bricks. By pumping it to a certain depth in the ocean where the temperature and pressure are just right, we might be able to store it in a wild form called clathrates, which are crystalline solids that look like ice, and which occur when water molecules form a cage-like structure around “guest” CO2 molecules. Although plenty of questions exist about how to actually store the CO2, the most prominent idea is to store it in deep geologic formations. The idea is to capture CO2 at the smoke stack of coal burning power plant, purify it, compress it and then pump it deep into the subsurface – at no small cost. This doesn’t help with the transportation fuel (yet), but gets at an accessible concentrated stream from a pretty important process that accounts for nearly half of our CO2 emissions.
 
Many of you have already been exposed to the idea of geologic disposal of nuclear waste. How do you feel about subsurface storage of carbon dioxide? Keep in mind, the oil we pump out of the deep subsurface has been there for millions of years, trapped below impermeable rocks. In fact, we could (and do) pump CO2 into depleted oil reservoirs; the only problem is that the oil reservoirs we have depleted are now perforated with wells, so the CO2 might leak back up. Therefore, many scientists are looking at other formations that are less well characterized (but less perforated). Pumping CO2 into deep saline aquifers is an option, but then the brackish brine that the CO2 displaced would be pumped out and need managing. Do you think super salty water would be a waste product or a possible resource?
 
Here are a few more questions about engineering to meet our lifestyle demands vs. re-engineering our life styles. Do you think we should manage the CO2 we produce by storage, or manage how much CO2 we produce? How much of a lifestyle change are you willing to consider to reduce your CO2 footprint? Would you rather pay a little more at the pump and on your electric bill so scientists and engineers can figure out how to dispose of CO2 waste from the fossil fuels we burn or would you consider never driving in a car if it didn’t have at least one other person in it? Could driving alone in cars eventually have the same social stigma as smoking cigarettes? Speaking of powering our cars, what if imported oil became less available? Do you think we should consider harder-to-get-to fuels such as oil shale in Colorado? It would mean building more roads and increasing the negative impact on the landscape – but we’d be more energy independent and developing the resource would create jobs. How important is energy independence for the US? If you were a policy maker, how would you determine the relative importance of energy development, economic growth, landscape degradation, and CO2 emissions to the atmosphere from any fossil fuel burning process?
 
Answering these questions isn’t easy for anyone, but a scientific basis for analysis and assessment helps us quantify and compare the various options. We’ll talk about some of these methods at the Café.