Friday, July 25, 2008

Geologic vs Biological Sequestration of GHG

The article below is talking about geologic sequestration, not to be confused with soil carbon sequestration. The difference? Geologic seq (often referred to as Carbon Capture and Storage or CCS) refers to capturing CO2 and pumping it underground into geologic formations (underground caves, caverns, mines, etc) and permanently trapping it there. Soil carbon seq, or biological seq - refers to using plants and roots to convert CO2 into carbon, and storing the carbon in the soil as part of the soil.

A key point to note: If geologic sequestration is found too have too many complicating factors -- or is too expensive to become commercialized, than there may be even more demand for biological sequestration and agriculture offsets in the carbon market.

Environment & Energy Daily

Long-term effects of carbon [geologic] sequestration concern lawmakers
(07/25/2008)Katherine Boyle, E&E Daily reporter

Capturing large amounts of carbon dioxide emissions from power plants in order to fight global warming may be feasible in the future, but members of the House Energy and Commerce Committee are nervous about unintended consequences.

At an Environment and Hazardous Materials Subcommittee hearing yesterday, Democrats and Republicans alike said they were concerned burying carbon dioxide (CO2) beneath the ground could be risky and cause new environmental problems.

Rep. Hilda Solis (D-Calif.), for instance, is worried about the effects earthquakes could have on buried carbon stores, particularly in California along the San Andreas Fault. "We're preparing for a big California earthquake," Solis said. She questioned the corrosive properties of CO2 as well and asked what might happen when it is combined with lead or arsenic.

Subcommittee ranking member John Shadegg (R-Ariz.) reminded the panel of the gasoline additive methyl tert-butyl ether (MTBE), which was used to reduce tailpipe emissions but later found to contaminate large quantities of groundwater. "It would be a grave error to move forward with technology that would replace one environmental problem with another environmental problem," Shadegg said.

"That is the framework in which the American people will view whatever we do at this point," he added.

Shadegg also questioned how well the United States has examined environmental damage from carbon injection used to force oil and natural gas out of the ground.

Rep. Joe Barton (R-Texas) suggested EPA should focus more attention on CO2 conversion. "It yields more baking soda than we'll probably need, but it's dramatically easier to store" than gas or liquid, he said.

'Ace in the hole'

Newly appointed subcommittee Chairman Gene Green (D-Texas) questioned how carbon sequestration could affect groundwater reclamation from saline aquifers, if the water in those aquifers could be purified.

This week, U.S. EPA released its proposal to regulate the underground injection of carbon dioxide by power plants and other industrial pollution sources.

EPA's proposed rule is aimed at protecting drinking water sources during and after the geologic sequestration process. In carbon capture and sequestration, CO2 is captured from fossil-fuel power plants, industrial facilities or other sources and then compressed. At the sequestration site, CO2 is injected into deep subsurface rock formations via one or more wells.

Proposed EPA permitting requirements address well location, construction, testing, monitoring and closure. The goal is to prevent CO2 from migrating into underground water supplies. If the gas infiltrates drinking water, it could push other substances that occur underground naturally, like salt, into the drinking water source. It could also create a corrosive carbonic acid that could lead to CO2 leaks (E&E Daily, July 21).

Benjamin Grumbles, EPA's assistant administrator for water, emphasized that the EPA proposal is only meant to address drinking water concerns.

He predicted carbon capture and sequestration could reduce greenhouse gases by 15 percent to 55 percent over the next century. "Geologic sequestration may not be a silver bullet, but it may be our ace in the hole," he said.

Scott Klara, director of the Energy Department's Strategic Center for Coal, said DOE is working with universities, private partners, regions and states to ensure geologic sequestration will be a safe and viable way to reduce greenhouse gas emissions. DOE is working with regional partners on pilot projects to learn more about the technology needed.

"The ultimate success of sequestration will hinge, in part, on our ability to measure the amount of carbon dioxide stored on a site, prevent environmental impacts and mitigate" any harmful effects, Klara said. Another essential aspect is determining whether adequate storage space exists throughout the United States and Canada, he added.

No comments: