It may sound like science fiction, but what if we could “scrub” all the carbon dioxide emitted from coal-fired power plants and inject it deep into the Earth, permanently locking it up in rocks? Well, this is fact, not fiction, and it’s called carbon capture and sequestration (CCS). And it turns out that the petroleum industry has already been successfully injecting carbon dioxide deep into the Earth for decades. In the sequestration part of the story, CO2 is injected into a porous rock, and locked deep in the Earth under an impermeable bedrock seal the same way fossil fuels have been for tens to hundreds of millions of years. In other words, we’re essentially putting the carbon back where it came from.
Sequestering CO2 underground on a grand scale is a critical piece in the fight to reduce CO2 emissions from thousands of coal-fired power plants around the world. A staggering 7 billion or more tons of coal are burned in the world each year and recoverable reserves are a hundred or more times that; so for the foreseeable future we acknowledge that coal is here to stay.
In a Feburary 3, 2010 memorandum, President Barack Obama said: “Rapid commercial development and deployment of clean coal technologies, particularly carbon capture and storage, will help position the United States as a leader in the global clean energy race.” Indeed, today’s technology can already capture carbon dioxide from the flue gas of a coal plant, compress it into a fluid and inject it into the earth where it remains permanently. What’s still needed is the regulatory pathway to allow this technology to be brought to commercial scale.
So today, the U.S. Environmental Protection Agency released two long-awaited rules that ensure that carbon dioxide (CO2) can be safely injected and permanently locked into deep rock formations. Geologic carbon sequestration (GS) technology promises to be a significant control option for the approximate 2 billion tons of CO2 that electric power stations release into the atmosphere every year in this country. This amount is estimated at one-third of this country’s total output of the primary climate-altering greenhouse gas.
Underground injection is a common practice in the U.S. Several billion tons of water fluids are injected into rock formations each year. But one of the petroleum energy industry’s best-kept secrets is called EOR, or enhanced oil recovery, injecting CO2deep underground in order to force out hard-to-reach oil. The good news is, however, that in the process of EOR, much of the CO2 remains behind, locked deep underground, permanently.
Underground injection of CO2 dates back over three decades by the oil and gas industry to improve the effectiveness of oil production in depleted reservoirs. Here’s how it works: sandstone reservoir rock is composed of small sand grains cemented together. But like a sponge, sandstone has 20-30 percent ‘pore space’ that can accommodate and trap oil and gas. In situations where no oil or gas is found in the sandstone, the rock pores typically hold fresh or saline water or “brine”. These are the subsurface regions geologists are targeting for CO2 injections. But how do we know it will stay there?
When CO2 is injected deep into rock and dissolved in formation water, it becomes more dense, fills the rock pores and tends to sink. EOR operators have found that when a ton of CO2 is injected, only half of it returns to the surface with the produced oil or gas, the other half is locked in the rock where the hydrocarbons once were. Because CO2 is a very expensive commodity, CO2 that surfaces with the oil or gas is easily and cost-effectively be captured and reused. Industry scientists have investigated the loss of CO2 and found that the “missing” CO2 is either irretrievably locked into the pores of the rock, or dissolved into the water in the rock.
So are there any risks to GS? For public health, most critical is the protection of ground water because without an adequate cap rock, movement of CO2 or brine displaced from the rock formation could conceivably leach into drinking water aquifers. Thus, one of today’s new rules is designed specifically to amend EPA’s Underground Injection Control Program (UIC) to protect groundwater from such risks. The rule will require careful siting of GS locations and the use of sophisticated surface and subsurface monitoring technologies to track the progress of CO2 as it is injected–to be sure it remains under the impermeable cap rock. In the second rule released today, the Greenhouse Gas Reporting Rule, EPA requires that GS site operators have a sound plan for monitoring potential leakage to the air and account for the volumes CO2 sequestered to confirm its permanent removal from the atmosphere.
Enhanced oil and gas recovery (EOR) is another important piece of the carbon dioxide sequestration puzzle. EOR fields are ready to be used to sequester CO2 from utilities upstream that may not have nearby geologic sequestration sites but do have access to a CO2 pipeline. EOR is critical for early-mover carbon capture projects, those undertaken during the period when saline regional GS sites are still being explored. With support from the National Energy Technology Laboratory (NETL) the Regional Carbon Sequestration Partnerships are investigating saline aquifers suitable for large-scale CO2 injections in all areas of the U.S. And because they are ready now to accept CO2, EOR sites are a key component of most of the Department of Energy’s ten or so pilot carbon dioxide capture projects under its Clean Coal Power Initiative (CCPI) funding.
So today, we commend EPA for its enormous step forward to ultimately control the CO2 emissions from new and existing coal- and natural gas-fired electric utility plants and other industries. However, we charge the agency to work quickly to develop cost-effective monitoring and accounting best practices that will encourage rather than discourage commercial development of saline and EOR GS. To do this, EPA should learn all it can from EOR and, at the same time, develop CO2 storage capacity in well-known EOR fields where CO2 infrastructure already exists and can be readily taken advantage of. And given the multidisciplinary character of this industry, EPA and the involved agencies such as NETL and U.S. Geological Survey should consider consolidating their expertise into a single interagency GS office.
Power plants that don’t emit greenhouse gases are not science fiction and will be an enormous step to a future without global warming.