Friday, February 5, 2010

Carbon Capture Could Be Key

If you've paid any attention to the green movement, you'll know that global carbon emissions have far outpaced natural levels, and that numerous efforts are underway to reduce emissions and the climate change they will cause.

But in spite of these efforts, “we are not on track to reduce global climate emissions,” Thomas Halsey of ExxonMobil Upstream Research said during a public lecture Wednesday. Renewable energy, improved transportation and energy efficiency have the potential to greatly reduce global emissions, but not to the degree that is necessary. If this is true, how do we fill the gap? One major factor will be carbon capture and storage - preventing carbon emissions from entering the atmosphere and causing warming.

“A lot of the carbon dioxide in the atmosphere comes from relatively concentrated sources,” e.g. power plants rather than car tailpipes, Halsey said.

A few technologies exist for capturing carbon at power plants, with varying costs and efficiency. Post-combustion CO2 filtration is commercially available already. Pre-combustion carbon capture separates CO2 and injects only hydrogen as fuel for the turbine. Demonstration plants exist, but are plagued by problems due to the complexity of the technology. Oxy-Fuel combusts pure oxygen, but requires very high temperatures and thus large amounts of energy (somewhat negating the positive benefits).

The one thing all three technologies seem to have in common is their high cost. In countries that have a carbon tax, like Norway, carbon capture is more feasible. But in the United States, adoption of the technology is slow-going.

And carbon capture is just one part of the equation. Once extracted, where could the CO2 be put to prevent it from entering the atmosphere? Enhanced Oilfield Recovery (EOR) is one possibility for use; when CO2 is injected into oil or gas reservoirs, it increases rates of recovery. EOR has been practiced for many years and is already in use at more than 100 oil fields, although many more could potentially benefit.

Carbon sequestration, the traditional option, involves injecting captured CO2 into the earth, into either unmine-able coal beds, deep saline aquifers or depleted oil/gas reserves. Geological barriers prevent the gas from returning to the surface.

Oil/Gas ReservoirsIncreased recoveryScale and capacity
Other people have drilled wells; might not know where they all are
Saline AquifersLarge scale, distribution and capacityLack of research
Unmine-able Coal BedsIncrease coal bed methane productionInjectivity problems (coal swells with CO2 injection and blocks pathways);
Pilot programs didn't work

Pros and cons must be carefully considered because “we don’t want to put the CO2 down and have it come back up,” Halsey said.

The Sleipner oil field in the North Sea, in use since 1998, has successfully injected 10 million tons of CO2 into an underground reservoir. Constant monitoring has shown some upward CO2 migration, but there is no evidence for leakage through the overlying shale barrier. The potential for earthquake activity is troublesome, but it is “a standard oil industry technical problem,” according to Halsey.

The monitoring required for such projects bring up an interesting issue-- who will be responsible for long-term storage stewardship? Companies would not be willing to invest if saddled with liability for hundreds of years. At some point, liability would need to be transferred to the public sector. Many issues exist, but if they are overcome, CCS could be a crucial tool for reducing catastrophic climate change.

Tuesday, February 2, 2010

How Do Rodents Make Decisions? A Nobel Laureate Speaks

Ion channels, the small tunnels that allow charged particles to flow through the cell membrane, play a significant role in various physiological functions. For neurobiologists, measuring the electric current associated with these ion channels proved to be a hard task, as a vast amount of information was lost due to noise.

The technique that was developed to overcome the loss of electric signals is called the patch clamp, and is one of the most widely used tools to study physiological processes on a molecular level today. One of the co-developers of this technique and a Nobel laureate, Dr. Bert Sakmann, was here on Friday to talk about his research at a seminar organized by the Duke Institute for Brain Sciences.

'We studied the neural connections in rodents using the Whisker model", Sakmann said to a packed auditorium.

The Whisker model was a whisker-dependent learning task in which the rodents had to make the decision whether to cross a small gap or not. "We wanted to know how many (neuronal) columns (of the brain were) involved in the decision-making process."

Through these experiments, Dr. Sakmann and fellow Nobel Laureate Dr. Erwin Neher identified certain cortical circuits that were activated during this decision-making process. "We measured the latency between stimulus and activation, and found there is a very precise and small latency."

They further discovered that decision-making is possible using a single column in the cortex. To measure the electric current associated within such single cells, they developed the patch clamp technique.

The patch clamp enabled the study of single ion channels and helped gain insight into the role of these channels in hormone regulation, heart diseases, epilepsy, and diabetes among others. A small video demonstrating the technique can be found below.

Sakmann and Neher received the Nobel Prize for Medicine in 1991 for their work.