by Richard T. Stuebi
At a recent symposium on climate change solutions at Oberlin College, I heard a presentation by David Ball, who leads the Midwest Regional Carbon Sequestration Partnership (MRCSP) at Battelle Memorial Institute in Columbus.
His presentation was a fascinating collage of facts and observations about the status and prospects for in-situ sequestration of carbon emissions from coal powerplants and other large point sources. To wit:
CO2 must be sequestered deep underground to avoid cross-contamination with water aquifers, and also to find the low-density “spongy” strata underneath the impermeable “caprock” strata. This tends to be on the order of several thousand feet below the surface. In order to keep the CO2 underground at these depths, given the high hydrostatic pressures that pertain so far below the surface, the CO2 must be compressed to approximately 100 atmospheres before injection. No wonder the energy/capacity penalty associated with carbon capture/sequestration is so significant!
The average coal powerplant emits about 24,000 tons per day of CO2. Meanwhile, the largest pilot project attempted to date in the U.S. for carbon sequestration has only dealt with a volume of 10,000 tons per day. In the North Sea off of Norway, the carbon sequestration effort led by StatoilHydro (NYSE: STO) at Sleipner has been sequestering about 2800 tonnes per day since 1996. In other words, carbon sequestration has not yet been performed in anywhere near the volumes associated with powerplant emissions.
Notwithstanding the significant volumes of CO2 emitted in the upper Midwest from our fleet of coal generation and large industrial facilities, there is enough regional underground sequestration capacity to hold “hundreds of years’” worth of CO2 emissions. This was news to me: I had heard concerns that the carrying capacity of the deep underground reservoirs suitable for sequestration would be small relative to our current emissions.
As with many of the cleantech challenges, carbon sequestration is not a question of if something can be technically done. Rather, it’s a question if it can be done at an out-of-pocket cost that will be acceptable to politicians and their constituents.
Recent conversations I’ve had with a Norwegian company named Sargas, which is developing a 95% carbon capture technology applicable to pressurized fluidized bed boiler combined cycle power generation facilities, indicates all-in costs (including capital recovery and returns) of under 10 cents/kwh, perhaps to as low as 7-8 cents/kwh. This isn’t too bad, but I suspect that the costs will have to proven at lower levels (or energy prices are otherwise going to have to rise much further) before many in the U.S. are assured that the potential economic impact of climate legislation won’t be severe.
And, of course, sequestration doesn’t address any of the concerns associated with mining the coal to begin with. For some ardent environmentalists, that makes coal unacceptable, even with cost-effective carbon sequestration. That said, practically speaking for voters and officials alike, it’s hard to overlook such an inexpensive and domestically abundant fuel.