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You heard McCain talk about it, you heard Obama support it in the presidential campaign as well. The clean burning of coal by means of capturing and sequestering its carbon exhaust. Let’s be clear. There is no tested technology existing today to produce "clean coal". Scientists don’t even know if it will work. It’s just a concept brought to you by the coal industry.
Keep in mind that coal plants supply roughly one-half of all electricity in the US! And since it is a domestic source of energy, this dinosaur of energy production has been looking real attractive to our leaders.
The clean coal concept refers to an array of technologies that sharply reduce pollutant emissions from coal-burning power plants. In the 1980s and 1990s, efforts focused on reducing emissions of sulfur, nitrogen oxides and soot — which cause acid rain, damage forests and pollute watersheds.
The latest and larger concern about burning coal is the production of greenhouse gases, especially carbon dioxide. This has presented the coal industry with an engineering challenge it has not been able to pull off.
Traditional coal combustion emits far more carbon than other fossil fuels. Thus, maintaining coal as an option for power generation (electricity), will require dramatically reducing these emissions. A breakthrough is critical to the long-term energy needs of the US, which is considered the "Saudi Arabia of coal." Coal represents some 90 percent of the nation's recoverable fossil fuels, with reserves sufficient for 200 years, at current rates of use.
Clean coal depends on being able to ‘capture’ carbon dioxide emissions and then to safely dispose of them indefinitely underground, in a process known as sequestration, capabilities not expected to be commercially deployable until 2020.
There are two leading approaches to meeting the challenge. The first is an advanced steam cycle technology, known as ultrasupercritical (USC) cycles. The other is integrated gasification combined cycle (IGCC) technology.
USC promises significant efficiency gains, which could reduce carbon emissions by about a third. The US, long a leader in advanced coal combustion technology, has 170 supercritical units in operation.
IGCC, which is still a few years from commercial deployment, promises a potential quantum leap, approaching zero-emissions. Full-deployment, however, depends on overcoming another technological challenge — not just the ability to capture carbon but also to safely dispose of it indefinitely underground, in a process known as sequestration. This is not expected to be commercially deployable until 2020.
The choice of technology is hardly academic. In planning for new base-load (constant) power plants, utility companies must choose plants with carbon capture capabilities or face steep future costs under anticipated new laws establishing a cost to carbon.
There are just four commercial-sized coal-fired IGCC plants in operation. Two are in Europe and two in the US, one each in Florida and Indiana.
There have been significant capital and engineering investments made in IGGC technology in recent years by a small number of industry leaders, including Conoco Phillips, Shell and GE.
The federal government made a significant commitment to advancing this technology through its $2 billion FutureGen project, but support was withdrawn in January 2008 because of cost overruns and concerns the technology might quickly become obsolete. The next administration is expected to revive support.
Despite the compelling need, there are precious few IGCC projects still being pursued. Known plans include one by Duke Energy and a joint project undertaken by Hydrogen Energy and Edison Mission Energy, a subsidiary of Edison International.
Are there other potential solutions?
Anticipation of some form of carbon controls (most likely a market-based cap & trade system) has stimulated investment in other ways to capture carbon. Most are a variation on how other pollutants have been controlled.
For instance, liquids or solids (or static electricity) are injected into the plant’s flue gas exhaust to capture particles. Carbon is currently captured by exposing flue gas to an ammonium carbonate solution, which is then heated under pressure, reversing the absorption process so pure carbon is recovered. Georgia Tech University researchers recently reported using a solid adsorbent called "hyperbranched aminosilica" to capture seven-times more carbon. The substance can be recycled and reused.
Another capture method uses chilled ammonia, with which Alstom has demonstrated (in a lab) a capture rate of more than 90 percent and at a far less cost. The company is running a pilot project at Wisconsin Energy’s Pleasant Prairie Power Plant.
Technologically-based upstart companies — as well as infrastructure firms — offer investors limited entry into this sector, which is for the most part dominated by large firms.
