Converting Oil Shale to Gasoline via Alberta Taciuk Processor Results in Full Fuel Cycle GHG Emissions 1.5-1.75 Larger Than From Conventionally Produced Gasoline
25 August 2009
| GHG emissions for ATP shale (low and high cases) and conventional gasoline in grams of CO2e per MJ of final fuel delivered. Credit: ACS. Click to enlarge. |
Converting oil shale to gasoline via the Alberta Taciuk Processor (ATP)—an above-ground shale retort—results in fuel-cycle greenhouse gas emissions of ~130-150 g CO2 equivalent/MJ of gasoline produced, according to a new analysis by Dr. Adam Brandt at Stanford University. These emissions are 1.5 to 1.75 times larger than emissions from conventionally produced gasoline.
The results depend most sensitively on the grade of shale used, and the rate of carbonate mineral decomposition which causes inorganic CO2 release, reports Brandt in a paper published online 25 August in the ACS journal Energy & Fuels.
Oil shale is a fine-grained sedimentary rock containing kerogen—a solid organic precursor to oil and gas—from which hydrocarbon gases and liquids (HCs) can be obtained through the application of heat. There are two basic approaches to processing oil shale: mining the rock and heating it in a surface retort, and heating the rock in the ground, to then pump up the resulting oil. The largest global oil shale deposits—estimated to be equivalent to 1,500 Gbbl oil equivalent—are found in the Green River formation of Colorado, Utah, and Wyoming.
Recent oil shale efforts have been spurred by US federal support for oil shale research and development, for example, the White River Mine research and development project, proposed by the Oil Shale Exploration Company (OSEC) in response to a Bureau of Land Management call for research proposals. The largest stage of the project was proposed to produce 1.8 Mbbl of shale oil from 2.7 Mton of raw shale, using a 250 ton/h Alberta Taciuk Processor (ATP) retort. More recently, OSEC has proposed using the Petrosix process, another oil shale retorting technology.
Also of importance is a recent project in Queensland, operated by Southern Pacific Petroleum(SPP), which also used the ATP. This project was terminated in 2004 due to cost overruns and opposition on environmental grounds. Current ATP development activities include the construction of an ATP retort for use in the Fushun shale of China.
—Brandt, 2009
In the new paper, Brandt models two large-scale deployments of the ATP which have low and high energy and GHG intensities—each of larger scale than existing operations. In each case, the ATP is applied to oil shales of the Green River formation.
The ATP fuel cycle comprises six stages:
- Mining and preprocessing of shale
- Retorting
- Disposal of spent shale
- Onsite upgrading of raw shale oil
- Refining of upgraded shale oil
- Combustion of refined liquid fuels
| Schematic of mass and energy flows in the ATP retort. Credit: ACS. Click to enlarge. |
The ATP retort has lower water requirements than previous surface retort designs, and can also utilize fine particles, thus reducing shale waste. Most or all of the retorting energy is provided by the combustion of char (a carbon-rich shale coke resulting from the heating of the kerogen that remains adhered to shale particles) and produced gas, making the process potentially energy self-sufficient from the point of view of the operator.
Incoming shale is heated to above 500 °C. The temperature of retorting is a design characteristic, Brandt notes, with higher temperatures resulting in shorter retort residence times and somewhat higher oil output. However, at temperatures above 600 °C, there is a tendency to reduce oil yield, likely by cracking of oil. Oil and noncondensable gases (HCs, H2, CO2, CO, and H2S) are removed from the retort as vapors, carrying energy with them. The retorted shale is then moved to the combustion chamber.
The high temperatures can cause carbonate minerals within the shale to decompose. When contained in oil shale, carbonates begin decomposing at ~565 °C (MgCa(CO3)2) or 620-675 °C (CaCO3), depending on the partial pressure of CO2 in the retorting atmosphere. In addition to the release of inorganic CO2, carbonate decomposition is endothermic, increasing the heat demand of retorting.
Brandt performed full life cycle assessments (LCA) for high and low energy cases. Among his findings were:
Producing 1 MJ of reformulated gasoline from shale via the ATP requires the consumption of 0.56 to 0.87 MJ upstream. For comparison, upstream consumption for reformulated gasoline produced from conventional oil is ~0.2-0.25 MJ/MJ fuel.
Much of the energy input comes from the fuel feedstock itself. Nearly all of the energy consumed by the retort is provided by the shale itself and much of the refinery energy input comes from the shale oil refinery feedstock.
Full-fuel-cycle GHG emissions are estimated to be 129 g CO2 equiv/MJ in the low case and 153 g CO2equiv/MJ in the high case. Emissions from carbonate decomposition are important in both cases. These are ~1.5-1.75 times those of gasoline from conventional crude oil on a full-fuel-cycle basis.
By varying key parameters in the model, Brandt found that the results are most sensitive to the richness of the shale: the lower the shale quality, the more inert mineral matter must be heated per megajoule of oil produced. Results are also sensitive to the level of carbonate decomposition.
In his discussion of the results, Brandt notes that the two cases analyzed are conservative and could underestimate the actual operating impacts of oil shale production using the ATP. Upstream energy inputs in the mining of the shale could be higher, and higher rates of carbonate decomposition could also be higher. In addition, the analysis does not account for fugitive methane emissions which could occur during shale and shale oil handling and processing.
It is instructive to consider the implications of a very large oil shale industry that does not practice CO2 mitigation. If we produce, refine, and combust fuel equal to 10% of 2005 US gasoline consumption (3.3 x 108 bbl/y, or 1.8 x 1018 J) from oil shale using the ATP instead of conventional oil, full-fuel cycle emissions could increase from about 42.5 million t of carbon (C as CO2) to 65-74 million t of carbon. This is a rough increase of 20 to 30 million t. To put these figures in perspective, emissions from all sectors in the state of Colorado equaled 24 million t of carbon in 2001. Thus, replacing 10% of US gasoline with shale-derived fuels produced using large-scale ATP projects would result in additional emissions commensurate with the total emissions from the state of Colorado.
Given the uncertainties involved and the potential for large GHG impacts from oil shale production with the ATP, more research attention should be focused on understanding this technology and mitigating its impacts. It is especially crucial that this occur before the development of an oil shale industry in the United States.
—Brandt, 2009
Resources
Adam R. Brandt (2009) Converting Oil Shale to Liquid Fuels with the Alberta Taciuk Processor: Energy Inputs and Greenhouse Gas Emissions. Energy Fuels, Article ASAP doi: 10.1021/ef900678d
No mention of water wasted.
Posted by: danm | 25 August 2009 at 11:08 AM
Why am I not surprised?
Posted by: Mick the Economist | 25 August 2009 at 11:18 AM
I can understand it from a technical point of view but this would be a desperate way to get gasoline. But then again look at the oil sands.
Posted by: aym | 25 August 2009 at 11:34 AM
Perhaps we could all decide to drive a little less and not do this to our planet.
Posted by: Nick Lyons | 25 August 2009 at 01:58 PM
If nuclear energy was used for retorting and to operate most of the various processus, the difference with conventional crude could be almost nil.
With regards to tar sands extraction and treatment, using the in-situ method and energy from a few very large nuclear plants, could reduce the environment impact below imported conventional crude and preserve NG for other uses.
Oil and Gas extracted from shales and treated with nuclear energy (heat and/or electricity) could also compete with imported crude from an environment point of view.
Somebody could redo this study using alternative ways and methods and arrive at very different results.
Owever, many other sources of chemical pollution are associated with tar sands and shales oil extraction. Those should also be addressed.
Posted by: HarveyD | 25 August 2009 at 03:07 PM
"If nuclear energy was used for..."
Orrrr we could use the nuclear energy to charge up BEVs through the grid and leave the fossil carbon in the ground.
Posted by: ai_vin | 25 August 2009 at 07:01 PM
"If nuclear energy was used for..."
The mining of oil shale had to be suspended for a decade or two until those nukes were finally built and they would put themselves out of business because the process would become to costly
Posted by: Arne | 25 August 2009 at 10:42 PM
The world cannot change to EVs in less than 25 to 30 years and a lot of liquid fuel will still be required for at least the next 50 years.
Using the 'in situ' method with heat/electricity supplied by nuclear energy instead of valuable NG could be very positive for the environment for the next 50+ years. The nuclear plants required would be worn out before tar sands and/or shales run out.
Of course, total extraction + processing cost may be more but everybody know that liquid fuel price will go up as it gets rare. Something like $200 a barrel by 2025/2030 is not impossible. Biofuels and other alternative liquid fuels will not be very cheap either. We will get use to $6/gal instead of $2/gal like EU countries did.
Posted by: HarveyD | 26 August 2009 at 09:03 AM
Two Candu reactors were built for China a few years ago in less than five years. It would only take seven in Canada. If they were smart enough to build a Candu reactor for boiling water only, it would be much faster and cheaper to build. Candu reactors get about 200,000 kilowatt hours thermal from a kilogram of natural uranium. This is roughly equivalent to 30,000 kilograms of coal.
Sasol gets about two barrels of liquid fuel from a tonne of coal. At the mine, a tonne can be had for $20 or less, and there is plenty of room for profit. At one time in the last three years crude oil was selling for 10 times the price of coal or more for the same amount of energy.
China is not going to continue to buy oil at $100, they will convert coal to liquid fuels. ..HG..
Posted by: Henry Gibson | 27 August 2009 at 03:05 AM
It must be clearly written:
Nothing that the US will do will result in the decrease of CO2 in the air. The advancing industries of China and India and other countries will far surpass any proposed efforts to reduce CO2 in the US. All of the mandates for biofuels and reduced use are simply taxes on the US economy that are directly routed to off shore industry just as all the jobs, salaries, FICA taxes, income taxes, sales taxes, industrial taxes, property taxes and money have been.
In the face of high oil prices, almost all gasoline consumers would buy gasoline at 2 dollars a gallon from oil shale rather than four dollars a gallon from foreign countries. If the US does not force people to not smoke it should not force them to buy imported oil when oil shale is cheaper. Gasoline can be made from coal to compete with gasoline made from oil at $35 dollars a barrel. Oil was selling for more than 20 time the price of coal for the same amount of energy recently.
The anti oil shale and anti coal-to-liquids publicity and actions are largely promoted by oil interests as are the anti-nuclear actions. They succeed by not telling the truth: "Low cost energy is required for a functioning industry and economy." The very high oil prices killed or sparked the killing of the world economy. The high oil prices were due to speculators who had to put their fake banking profits somewhere to take more money out of the wage earners pockets. Another victory over the oil producers like that of France would be intolerable.
The US had an opportunity to reduce the CO2 that the world produced 30 years ago. More workers were killed by the recent hydro electric pipe failure than have ever been killed by a reactor failure. At Chernobyl less than 50 were killed, and most of those were not killed by the accident but by the USSR's failure to safegard emergency workers who were forced into dangerous positions. Very few others have died since with causes even possibly proveably related to radiation from Chernobyl.
All plants and animals and most soils have always been radioactive from the beginning of the earth. The billions of rays that the body puts out every day and the many more that come from the earth and sky have less effect than the billions of organisms that inhabit the body.
The US could have instigated and caused the building of nuclear reactors to replace all coalfired generators and it would have not doubled the price of electricity to the average consumer at any time. It would have reduced it with many standard, quickly built reactors. and other countries could have built the same reactors.
CANDU reactors can be built in less than five years, and do not need enriched uranium.
There was always the example of France who started building more reactors at the first oil price increase. They alway had the option of buying Coal in the US. They also reprocessed fuel, so that they did not waste more than 98 percent of the uranium mined like the US does and did in a failed attempt to appease the world into doing what the US thought was best for them.
Anybody could have found out in 1970 the general principles of building a plutonium production reactor like those at Hanford and built much better ones using heavy water. It had been 30 years since the first plutonium was made. Methods of separating heavy water had become so efficient that Canada allowed their separator to be torn down with vast stocks on hand.
Anybody who knew the basics of building a plutonium bomb knew that the plutonium in spent US fuel rods was worse than nothing because it did not have the correct mixture of the various highly radio-active isotopes of plutonium which could not be easily separated from each other. They would know that it would be easier to get uranium from granite, even, and separate the low radioactive uranium isotopes.
France devotes three quarters of the power of a nuclear reactor to separate uranium isotopes. It would be more cost effective to ship the power a few hundred miles and have URENCO do it. It is possible that replacing part of the light water in standard reactors would lengthen the life of the fuel substantially.
The fuel in used French fuel rods could be used with only slight repackaging in CANDU reactors. The same is true for most countries. China and Korea will actually never have to buy uranium fuel for their CANDU reactors, but it is easier to use new uranium. One kilogram of it produces 60,000 kilowatt hours, so uranium is not a big part of a Frenchman's electric bill even at $1000 a kg. China gets a lot of uranium from coal ashes.
By not generating electricity with oil at $100 France may have saved 100 billion Euros. Enough to buy ten or more nuclear power plants. ..HG..
Posted by: Henry Gibson | 27 August 2009 at 03:37 AM
H.G.
Interesting arguments.
The anti-nuclear lobbies, financed by ...., will continue to fight for decades to stop further use of a sustainable source of cleaner energy.
Lately, anti-wind energy lobbies have managed to stop development of many wind farms in our province.
Anti-hydro lobbies + natives lobbies have delayed further hydro development in Labrador and Quebec for decades in oreder to raise the compensations (give aways) to several 100s $M.
Will anti-garbage lobbies rise and force cities and towns to convert all their wastes to clean electricity? Why not?
Will anti-GHG lobbies force coal burning power plants to clean up their acts and vehicle manufacturers to produce clean units?
One way to force China and India (and other similar producers) to create less GHG to produce goods they export to us would be to apply heavy GHG import taxes (10x carbon tax equivaent) on all such goods. Of course, we would have to be very careful not to create the same level of GHG, or even more, when the same goods are produced locally. We have not been very good world examples. USA and Canada already have one of the highest per capita GHG. It could be much higher if we produce more goods locally.
When we transfer manufacturing to other nations, GHGs go with it.
Why bark at China and India when they produce more GHG to manufacture goods for us?
Posted by: HarveyD | 28 August 2009 at 08:49 AM