U.S. carbon dioxide emissions are being significantly reduced by a combination of strong proposed limits on emissions from power plants and the shale gas boom. Coal-fired electricity generation has fallen from a 52% market share in 2000 to a projected 37% for 2012. Two thirds of that decline is being replaced by natural gas-fired generation that emits 50 percent less CO2, and the rest, happily, by increased renewable energy use.
Conventional wisdom has been that, even with these trends, we’ll have to capture the carbon emissions from any continued combustion of coal and store them safely underground to slow a runaway climate. But with temperature records being shattered and global water cycles intensifying at frightening rates, it’s clear that we must apply carbon capture and storage (CCS) to gas-fired generation as well.
I’m going to oversimplify a lot of technical issues and suggest six basic reasons why the time to do this is now.
First, CCS technology is here. It’s already being used successfully to inject captured CO2 into depleted oil wells to increase production. It allows for the capture of 90 percent of the CO2 emitted from natural gas combined cycle (NGCC) power plants.
Second, natural gas-fired power’s carbon advantage over coal serves to reduce not only the cost of capture, but also the costs and the amount of underground storage space needed. While the US appears to have centuries of CO2 storage capacity, this is also important because shale gas exploration may present potential conflicts with CCS that need to be better understood.
Third, the price of natural gas is low. The cost of retrofitting a natural gas plant with CCS has been estimated at $80 to $100 per ton of CO2 captured. Similarly, in 2007, the National Energy Technology Laboratory (NETL) calculated the cost for a new NGCC plant with CCS at $83/ton. This estimate was based on natural gas priced at $6.75/MMBtu. The price of gas today is 60% less than that, though it’s bound to rise as the current market glut balances itself. Still, lower gas prices argue in favor of applying CCS to gas-fired power now.
Fourth, CCS and gas-fired generation technologies are constantly improving. An NGCC plant that’s equipped with CCS has reduced energy output because the CCS system needs power to operate. Five years ago, NETL studies said that NGCC plants would run at 51% efficiency without adding CCS equipment and 44% with it. Today, gas plants efficiencies without CCS are at 60% and climbing, based on what I heard at CERAWeek 2012. So, the relative costs of CCS in gas plants is coming down.
Fifth, states are moving on CCS. CCS has always been assumed to need a Federal regulatory driver - a tax on carbon emissions, for example. But California law now mandates greenhouse gas emission reductions of 25 percent by 2020. Since gas plants provide about half of California’s electric power, WESTCARB has begun a study of retrofitting California natural gas plants for CCS.
Finally, it’s possible to improve the economics of CCS even further, thanks to the work of another state - Pennsylvania. During my tenure at the Pennsylvania Department of Conservation and Natural Resources, I led some of the nation’s most advanced planning work on CCS, a key component of which was completed with the invaluable help of the Clinton Climate Initiative.
The Pennsylvania approach relied on economies of scale to drive down CCS costs. Individual CCS projects are inherently expensive per unit of carbon captured. Pilot projects often lack the potential for scale up that would ensure commercial deployment. A network approach to CCS - a cluster of emitters (in our case, coal-fired power plants) sharing a common transportation and storage infrastructure – could overcome those problems. A CCS network could leverage investment in plant retrofit, share pipeline and storage infrastructure, and design for scale-up at inception, all lowering costs. Indeed, the initial assessment of a Pennsylvania CCS network indicated that it would be competitive compared to both proposed and existing international CCS projects. Preliminary estimates for network capture and transmission costs came in at $47 - $73/ton. These are well below NETL’s cost estimates for an individual NGCC plant. So, a network approach to CCS has promise.
It’s time to get serious about applying CCS to all fossil-fuel based electricity production.