One hears a great deal these days about the possibility of sequestering carbon dioxide produced by burning fossil fuels. As is typical of the conversation about energy and the environment these days - in particular the preeminent environmental issue of climate change - most of these schemes do not involve a discussion of capacity that currently operates on a scale that begins to approximate the scale of the problem.
The scale is clear enough: As of 2004, the world was adding carbon dioxide to the atmosphere at a rate of 27 billion tons per year. This is a rate that is 26% higher than 1990, which was supposed to be the Kyoto reference year, although Kyoto – for most countries at least – is more notable for being breeched than being effective.
Let’s be clear about something else: The impact of this carbon dioxide release is not something we are going to see someday if we don’t straighten out our act. I want to emphasize that time is short in the following discussion, because my impression is, that even after all of this, people seem not to recognize that it is not particularly useful to discuss something that could theoretically be available in 50 years or 20 years or even 10 years.
On the contrary, as Al Gore demonstrated in his now famous film, “An Inconvenient Truth,” the effects are with us right now. It follows that we have zero days left to prevent climate change and anything we do will merely slow or at best, I think, arrest it’s further development. Reversal of the implications of climate change is very unlikely, forests and species, agricultural land, and habitats dependent on the great glaciers have already disappeared. Further we have no way of assessing whether we have already entered a positive feedback loop that will entail even greater damage than we’ve already seen. Al Gore is my political hero, but I am jaded enough to recognize that appeals to heroism are at best dubious. If Mr. Gore runs for President, I will vote for him enthusiastically but to my way of thinking, Mr. Gore’s film was far too optimistic as well as a bit too facile about how one might confront this international crisis – possibly the worst crisis since the dawn of civilization, the one that makes other issues, like say, the war in Iraq, pale by comparison.
As we review out options therefore, it is important that we distinguish what we would like to have and what is available, what technologies might be available and what is industrially planned or industrially available "off the shelf." Some people want to say that sequestration is "off the shelf," because there are some sequestration facilities that exist, just as some people want to say that solar energy is "off the shelf" because one can buy solar cells at Home Depot. It is true that these things exist, but it is extremely important that we recognize that these things are not available on scale.
Solar energy, for instance, 50 years after the invention of the solar cell produces 0.01% of the world’s electricity. People love to wax romantic about solar energy and sing loudly about the growth potential of the industry. That’s fine, but it’s not even close to being enough. Although demand for solar cells is way up, as is manufacturing capacity, the solar industry has recently been characterized by shortages and supply problems – despite its tiny contribution. People don’t like to hear this but there is no evidence whatsoever that the industry could scale in most of our lifetimes to meet 20% of the world’s electricity demand – still leaving us 80% of the problem. Similar “Inconvenient Truths” could be asserted about other options.
I want to focus for now on just one of those options: Carbon dioxide sequestration in geographical formations.
Recently I encountered a publication that represents a comprehensive review of the available technology for sequestration and the costs involved. The report is here.
The study was part of a German evaluation of this technology. Germany, in case you don’t know, is a country that a few years ago announced a “phase out” of nuclear energy. More recently it announced that its new coal capacity that it is building in lieu of nuclear plants will be exempt from carbon accounting on the grounds that they are new. Although Germany has announced 8 new massive coal plants, it has committed to a much smaller plant that will “demonstrate” sequestration.
Similarly, we have in Norway – a country that after years of relying on hydroelectric power for almost all of its electricity has just built its first fossil fueled plant, a gas plant – a plan by Statoil to sequester about 1 million tons of carbon dioxide in its North Sea oil fields. We are not supposed to notice of course, that the purpose of this “sequestration” is actually to drive out more oil from the depleting fields, oil that will be burned most likely in automobiles and released into the atmosphere of carbon dioxide.
BP has announced that it intends to sequester 4 million tons of carbon dioxide per year in Carson California, carbon dioxide that will be created to produce hydrogen for local oil refineries. Of course the real purpose of this sequestration is to – you guessed it – to push more oil out of the ground to be burned in cars.
Why these strategies almost always involve oil is made clear from the study I just referenced. Sequestering carbon dioxide costs money big money. For this reason there is still no real economic reasons for anyone to really sequester significant amounts of carbon dioxide. It is far cheaper to talk about sequestration or to represent oil field practices as environmental practices, although they are no such thing.
Note that none of these projects even remotely approximates an ability to sequester a significant portion of the 27 billion tons we released in 2004.
Now some excerpts from the report.
Reducing CO2 emissions associated with power production by measures such as efficiency improvements or switching to low carbon fuels are limited by the residual carbon content of the fuel and the availability of the primary energy sources, respectively. Also, the utilization of renewable energy sources is restricted by capacities, as well as by the high cost of the present state of this technology...
...Apart from nuclear energy, CO2 capture and storage by far offers the largest potential for reducing CO2 emissions at lower costs than utilization of renewable energy sources . Although CO2 avoidance by efficiency improvement at a certain point will start to get very expensive compared to CO2 capture (Figure 1), the development of a low emission, i.e., highly efficient, power plant is advantageous for the application of CO2 capture. The capture requirements would be reduced in proportion to the lower CO2 emissions. Regarding CO2 storage, there are potential options; however, there are possible ecological problems in CO2 storage in the ocean, safety problems in underground storage, and impact problems of possible increases in primary energy consumption that must be considered and understood before this technology is feasible on a large scale. .
The bold and italics are mine. With respect to safety problems I would like to note something that may not disturb everyone else, but certainly disturbs me. In 1986, at a place called Lake Nyos in Cameroon, 1800 people and 3500 animals were killed in a matter of minutes when the lake suddenly, for reasons still not entirely understood, released 1.6 million tons of stored carbon dioxide. The death toll wasn’t greater because the area was sparsely populated. BP plans to sequester 4 million tons a year, meaning that in just 4 years of operations they will put 10 times as much carbon dioxide beneath Carson, California as was released at Nyos. In contrast to the rural communities around Nyos, Carson, California – where I lived for about 6 months back in the 1970’s – has 90,000 people. The adjacent community of Torrance has 120,000 and Lomita has 20,000. Moreover the area is crisscrossed by important earthquake faults, including the Crenshaw fault that runs almost directly down the center Crenshaw Blvd where there are lots of refineries. Further, the entire area, including many parking lots of commercial facilities is chock full of oil wells, many of which I would imagine stopped functioning long ago, and many of which are probably forgotten.
Draw your own inferences.
Table 2.1 contains a summary of the various power plants, which have either already been introduced, as of today, or are currently under development, together with improvement measures and efficiency potentials. The most important measures for improving efficiency involve increasing steam temperatures and gas turbine inlet temperatures, and improving waste heat utilization and component efficiency . Of all the power plants currently capable of being built, natural gas-fired gas turbine combined cycle (GTCC) power plants (Table 2.2) achieve the highest efficiency, lowest CO2 emissions and lowest costs (Table 2.2).
The most common coal-fired power plant is the steam power plant with pulverized coal combustion at atmospheric pressure. Coal-fired combined cycle power plant cycles with pressurized fluidized bed combustion (PFBC) are commercially viable, but display limited efficiency (43%); integrated gasification
combined cycle (IGCC) power plants (Figure 2.1) are in the demonstration phase, and pressurized pulverized coal-fired combined cycle power plants are at an early stage of development. Among the coal-fired power plants, the greatest level of efficiency, at current levels of technology for coal-fired plants, is attained by the IGCC power plants. This is why a large proportion of studies on CO2 capture in coal-fired power plants suggest the IGCC power plant . Another advantage of the IGCC power plant, in terms of CO2 capture, is that this is the only type of coal power plant, which allows CO2 to be separated, prior to combustion, from a gas flow, which is not diluted with air. According to recent studies, there is now virtually no difference between the electricity generating costs of coal-fired steam power plants and IGCC power plants of the next generation, in cases where the annual utilization factor is high...
Again the bold is mine, intended to emphasize the “off the shelf” criterion I suggested earlier. Note that this paper dates from 1999. Note that the sequestration technology discussed does not address existing systems all that much. This seems to imply “all new stuff.”
Table 2.2 gives the generating cost of IGCC coal plants as 3.6 cents/kw-hr.
Storing global, anthropogenic CO2 emissions amounting to 6 Gt C, corresponding to 22 Gt CO2 per year, requires global storage capacity on a scale of up to several hundred Gt of carbon. There are a variety of sinks and storage options, e.g.:
depleted oil and gas fields, as well as enhanced oil and gas recovery through CO2 injection,
CH4 recovery from coal seams by injecting CO2,
aquifers in geological formations,
oceans (largest capacity),
fixation in biomasses (afforestation, biomass fuel) or
solid CO2 (dry ice) repository: storage in a thermally insulated sphere of dry ice, with a diameter of
approximately 200 m (dry ice repository with limited storage period) .
A summary of storage capacities, storage duration and costs involved in the sequestration process is given in Table 2.3.
The Strait of Gibraltar has been proposed as a suitable ocean location for CO2 sequestration, based on the fact that strong currents from the Mediterranean would thin out the CO2 and transport it to deeper 10 Power Plants with CO2 Capture
regions of the Atlantic...
In all cases where CO2 is to be transported, stored or further processed, it must be compressed at high pressure. As a result, it is nearly always necessary to take into consideration additional energy consumption or an additional efficiency penalty (Table 2.4). The pressure required (Table 2.5) is generally greater than the critical pressure of 73.858 (Table 2.6). The low critical temperature of 31.05 ºC means that this nearly always involves liquefaction of the CO2. Pipelines enable the transportation of large mass flows of CO2. The USA, Canada and Europe all have many years of experience in transporting CO2 through pipelines several hundred kilometers long, in the context of CO2 injection for the purpose of Enhanced Oil Recovery (EOR). Operation of these pipelines has been shown to make more economic sense at supercritical pressures that at lower pressures [63, 64, 65]. Depending on the pressure drop over the total distance, and the differences in elevation of the pipeline, the most suitable pipeline inlet pressure has been cited as high as 172 bar [66, 67, 70].
According to Riemer and Ormerod , specific transport costs lie in the range of 0.6 US$ per t CO2 and 100 km pipeline length for pipelines in the sea, and 0.8 US$ per t CO2 and 100 km pipeline length.
I can’t of course, excerpt the entire study although there is some interesting stuff in there, an I recommend leafing through it, if your interested. Of particular interest, to cut to the chase, is a description of costs. At the low end, they can be “only” about 30% higher for IGCC plants using membrane carbon dioxide separation coupled to CO shifts – wherein the carbon dioxide is actually used for industrial purposes. (I have written about the hydrogenation of carbon dioxide to make the ultra clean motor fuel DME here before, but strictly put this is not sequestration but reuse of the carbon dioxide – it would reduce but not eliminate carbon outputs by displacing oil and not coal.) On the high end, the costs can be 180% greater.
Note that none of this, involves the cost of the fuel itself – or the environmental problem of coal mining and coal ash disposal.
In sum, though, I think the case is well made that sequestration is not really more than a pipe dream. It cannot be made available in time, and if it does become available, it is dubious in any case.
For the record – just in case any suspicion of my agenda is hidden – I am a might be available and what is industrially planned or industrially available "off the shelf." Some people want to say that sequestration is "off the shelf," because there are some sequestration facilities that exist, just as some people want to say that solar energy is "off the shelf" because one can buy solar cells at Home Depot. It is true that these things exist, but it is extremely important that we recognize that these things are not available on scale