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NETL Report Concludes CTL Plus Carbon Capture Results in Fuel with 5-12% Less Lifecycle GHG Than Petroleum Diesel; Modest Biomass Additions Lower GHG Further

Lifecycle GHG emissions of CTL/CBTL/BTL compared to 2005 petroleum diesel baseline. Background colors of the cells represent the crude oil price required for economic feasibility. Tarka et al. (2009) Click to enlarge.

A new report from the US Department of Energy (DOE) National Energy Technology Laboratory (NETL) concludes that coupling a Coal to Liquids (CTL) process with carbon capture and sequestration (CCS) yields a fuel with 5-12% less lifecycle greenhouse gas (GHG) emissions compared to the average emissions profile of petroleum-derived diesel, based on the US national average in 2005. These synthetic fuels are economically competitive with petro-diesel when the crude oil price (COP) is at or above $86 per barrel (based on a 20% rate of return, in January 2008 dollars, with a carbon price of zero).

Adding biomass to the coal in the CTL process (Coal and Biomass to Liquids, CBTL) can reduce the GHG emissions further, according to the study. A mixture of 8% (by weight) biomass and 92% coal can produce fuels which have 20% lower life cycle GHG emissions than petroleum-derived diesel and which are economically competitive when crude prices are equal to or above $93/bbl.

According to the NETL report, the addition of CCS to CTL is relatively inexpensive, adding only 7 cents per gallon to the Required Selling Price (RSP) of the diesel product. Increasing the percentage of biomass in the feed further reduces the life cycle GHG emissions of the fuel, but also increases capital and operating costs due to the higher cost of biomass feedstock and reduced economies of scale, the NETL report notes.

Diesel produced in a biomass only—i.e. Biomass to Liquids (BTL)—process only becomes economically competitive when the GHG emission value exceeds $130/mt CO2 equivalents (CO2e) and does not result in greater reductions in net GHG emissions than if the biomass were used in a CBTL plant, according to the report.

Based on these findings, it is anticipated that CTL and CBTL with modest biomass percentages (less than thirty percent by weight) would, as a part of the United States’ energy portfolio, provide a balanced solution to the nation’s transportation fuel dilemma, providing affordable fuels from domestic feedstocks, and enabling significant reductions in GHG emissions.

—Tarka et al. (2009)

The study evaluated the performance and cost of three types of plants (CTL, CBTL and BTL) in 11 different configurations at capacities up to 50,000 bpd. Feeds of 8, 15 and 30 wt% biomass were evaluated for the CBTL cases.

The study used two types of CCS configurations: a default, or “simple CCS” configuration, and a second “aggressive CCS” configuration in which equipment is added (at additional cost and performance penalty) in order to further reduce CO2 emissions from the CBTL process.

The “simple CCS” is a low incremental cost option for CCS, as it is functionally identical to the “without CCS” cases— CO2 is already captured within the CTL/CBTL/BTL plant as part of the process. Adding a CCS function requires the addition of CO2 compression, transport and storage capital and operating costs. The default option results in the capture of 91% or more of the CO2 produced by the plant.

The aggressive CCS configurations also utilize ATR (auto-thermal reformer) and WGS (water gas shift) reactors to attain increased levels of CO2 capture. The ATR unit partially oxidizes the light hydrocarbons (C2-C4) in the tail gas to CO, producing H2 as a by-product and making it possible to capture carbon which would otherwise be combusted and emitted as CO2. The aggressive CCS configuration can capture more than 95% of the CO2 produced by the plant, although this additional level of capture incurs both an efficiency and cost penalty which in many cases makes this plant configuration not preferred economically, the study found.

GHG Emissions of CTL/CBTL Plants Compared to Petro-Diesel
Case 1 2 3 4 5 6 7 8 9 10 11
Capacity (bpd) 50,000 50,000 50,000 50,000 50,000 50,000 30,000* 30,000* 5,000* 5,000* 5,000*
Biomass% 0 0 0 8 15 15 30 30 100 100 100
CCS None Simple ATR Simple Simple Simple ATR ATR None Simple ATR
WTW GHG Emissions
(kg CO2e/mmBtu)
235 90.2 83.7 76.0 63.4 35.1 55.3 23.8 -8.8 -210.0 -245.0
Change from petroleum +147% -5% -12% -20% -33% -63% -42% -75% -9.2% -321% -358%
* Plant capacity reduced from 50,000 bpd due to a scenario in which there is limited availability of biomass (4,000 dry tons per day.)

The study took no credit for soil root carbon, i.e. the accumulation of carbon in the soil and roots of energy crops, as there is some question as to the appropriate accounting method which should be used for this carbon. The authors note that the report therefore may understate the potential GHG benefits of biomass usage. While that has little effect on the overall economic findings, it could result in CBTL fuels which produce net zero GHG emissions with as little as 35-40 wt% biomass, according to the authors.

The study used one feedstock of each type—bituminous coal and switchgrass—to evaluate the CTL/CBTL/BTL processes. These were chosen as representative feedstocks for a Midwest plant location. Other coal and biomass feedstocks will be evaluated in a later study.

EPA and EISA 2007. The NETL findings are in contrast to an earlier analysis by the Environmental Protection Agency (EPA) which found that fuel produced by a CTL plant equipped with CCS had GHG emissions which were 3.7% greater than petroleum-derived diesel fuel, using fuel produced in the year 2017 as a basis of comparison. NETL, however, concluded that diesel fuel from CTL with CCS has life cycle GHG emissions which are 9% to 15% below that of petroleum-derived diesel, when a petroleum base year of 2017 is assumed (as in the EPA study).

The difference is critical for the development of CTL/CBTL fuels.

These preliminary findings from the EPA led lawmakers to insert language into the Energy and Independence & Security Act (EISA) of 2007 to preclude the use of fuels with a higher GHG footprint than those produced from petroleum, effectively discouraging domestic CTL development. This study clearly demonstrates that the use of the EPA feasibility study resulted in a misguided characterization of the life cycle GHG benefits of CTL with CCS.

...In CTL plants, a fuel can be produced which has 5% and 12% less life cycle GHG emissions than petroleum-derived diesel, using carbon sequestration, and sequestration coupled with aggressive capture, respectively. Therefore, CTL with CCS clearly meets the EISA 2007 criteria of producing a fuel with less life cycle GHG emissions than petroleum-derived diesel and federal agencies will be able to procure this fuel.

Furthermore, by co-gasifying a modest amount of biomass—8% by weight—the GHG emissions profile of the fuel is reduced to 20% below that of petroleum-derived diesel. Co-gasification of 15% and 30% (by weight) biomass results in emissions reductions of 33% to 63%, respectively. Additional reductions in GHG emissions can also be achieved through the use of aggressive CCS.

—Tarka et al. (2009)

Rentech study. Separately, Rentech, Inc. released summary findings from a third-party lifecycle assessment of the carbon footprint of synthetic fuels to be produced at its proposed CTL Natchez plant. (Earlier post.)

The WTW greenhouse gas analysis of the proposed Natchez facility, which includes CCS, concluded that the fuels from the facility would produce 11% to 23% fewer carbon dioxide emissions than would result from fuels produced from conventional crude refining.

Rentech proposes using petroleum coke as feedstock with the Rentech Fischer-Tropsch process to produce approximately 30,000 barrels per day of synthetic fuels, specialty waxes and chemicals. The facility is designed to capture approximately 80% of the carbon dioxide generated in the production process, which will be sold under a long-term agreement with Denbury Resources for enhanced oil recovery in the region.

Rentech says that it will publish the full study when it is available.




So the conclusion is that CTL with carbon capture (a best case scenario) can never be made sustainable since it cannot be made 100% CO2 neutral.

Bio ethanol can also be made with carbon capture and the current use of natural gas in the production of it can be replaced with electricity from CO2 free sources. Fertilizer to grow the needed corn or biomass can be synthesized with electricity from CO2 free sources instead of using natural gas and the diesel to harvest, transport and distribute can be replaced with ethanol or sustainable biodiesel. If all these efforts were combined the production of bio ethanol would surely be CO2 negative and could be used as a mechanism to decrease the CO2 level in the atmosphere instead of increasing it.

To quote James Hansen, Nasa's Goddard Institute for Space Studies "Coal is 80% of the planet's problem . . . You have to keep your eye on the ball and not waste your efforts. The number one enemy is coal and we should never forget that."

The proponents of CTL are among the poorest of human beings either in terms of their ignorance for the damage caused by the CO2 (which is forgivable) or in terms of their moral standings (which is unforgivable).

Nick Lyons

Coal=carbon sequestered by Mother Nature. We should leave it in the ground, because once dug out and burned, we will never get that carbon sequestered so securely again.

Liquid fuels are great--energy dense and convenient. Let's make them in a sustainable way.


I disagree Henrik. I'm thinking coal-to-ethanol, then ethanol-to-hydrogen (for fuel celled vehicles/trains/planes), with waste CO2 from ethanol-to-hydrogen process (using a catalyst sent to algae biorefinery to make more ethanol or biodiesel. I don't know all the specifics and may be naive, but I still think it can be done someway somehow.


Nick & Henrik - you guys might be right...but don't you think CO2 generated from coal-to-ethanol and ethanol-to-hydrogen could all be sent to an algae biorefinery for more biofuel? I'm not an engineer by training but it seems possible to get rid of CO2 entirely.


Bottom Line: CTL is a joke.



First; the carbon capture can never be 100%, CTL will always leave some behind.

Second; plants [like algae] can easily take all the CO2 they need from the air. You can speed up their grow somewhat by adding more CO2 but the real limit to their grow is the shortage of other things- like water, fixed nitrogen, trace elements, etc.

Third; sure we COULD do something like that but 'could' doesn't equal 'should.' Not when other ways may be better.


In the end when oil goes back up in cost we will see alot of ctl plants open up. It just depends on when they expect oil to STAY above 100 bucks a barrel.


Fourth; this report "concludes that coupling a Coal to Liquids (CTL) process with carbon capture and sequestration (CCS) yields a fuel with 5-12% less lifecycle greenhouse gas (GHG) emissions compared to the average emissions profile of petroleum-derived diesel" but that "average emissions profile" is for petroleum-derived diesel without CCS. CCS can be coupled to any stationary emission source, including the oil refineries that produce diesel so is the comparison fair?


Fifth; CCS has its own costs. One such cost is the energy you need to run it, basicly you'd be burning 40% more coal to take 80% of the CO2 out of the smokestack and keep it out of the air for 100 or so years.


We need to utilize everything in out power to reduce our dependence on foreign oil including using our own natural resources.OPEC will continue to cut production until they achieve their desired 80-100. per barrel. The high cost of fuel this past year seriously damaged our economy and society. Oil is finite. We are using oil globally at the rate of 2X faster than new oil is being discovered. We need to take some of these billions in bail out bucks and bail ourselves out of our dependence on foreign oil. Jeff Wilson has an eye opening new book out called The Manhattan Project of 2009 Energy Independence Now. He explores our uses of oil besides gasoline, our depletion, out reserves and stores as well as viable options to replace oil and the pros and cons of each. Oil is finite, it will run out in the not too distant future. WE need to take some of these billions in bail out bucks and bail America out of it's dependence on foreign oil. The historic high price of gas this past year did serious damage to our economy and society. WE should never allow others to have that much power over our economy again. I wish every member of congress would read this book too. There could be no better investment in America than to invest in America becoming energy independent. Create cheap clean energy, millions of badly needed new green collar jobs, and reduce our dependence on foreign oil all in one fell swoop! America needs to wake up and smell the coffee.


So, at an equivalent price of around $200/bbl we could have 100% biomass to liquids with CCS !

They calculated 20% return of investment.
So macro-economically it would cost only $160/bbl. (assuming the return is to american shareholders/governement instead of Saoudi kings).

Secondly, since most of that money would go to farmers and workers collecting the biomass and to workers in the factory, after they paid their taxes, it's only around $100/bbl.
Since many of them will not be on wellfare anymore, it will be even less.
Once these people spend this extra money in the own economy, even more returns to the own economy.

I am still calculating only for the first year, because once the initial investments are done, the economy will keep on running and making it cheaper. The return of investment will keep on coming, year after year.

In the long run, the stimulus of the own economy will keep on returning, while investment in oil-dictatorships will force us to invest more in the military.

So even this utopian fuel is cheaper than the oil of last/next year !

In addition, it is very, very clean fuel, since every gallon you consume drives CO2 OUT of the atmosphere !


ai-vin's comment about the Algaes ability to use extra co2 is spot on the whole article uses some very clever language and assumptions.
There is likely a requirement for C02 in the Bio- reacter model, along with every other "life support requirement"
These models are totally flawed IMO and even then the requirement is very much smaller than the volumes that would be generated.
Some readers will be thinking that the methods described will give 0 emission or better fuel and the report does nothing to discourage this assumption.
Nick is correct to say that the coal is CCS. It may be obvious to some that the sequesed CO2 value for coal to the climate model is higher than any other value for this material.

There is no proposal for tailpipe capture effectively there is no such thing as CCS from coal derived fuels any more than there is from petroleum fuels.

Fuel cells would offer such oportunity.
Fuels built utilising C02 upgrading and renewable electricity sources as well as Alcohol fuels will go a long way towards reduced emission, but any conventional application is likely (according to common perception) likely to increase the total CO2 emission.
In fact the tailpipe emissions will only be improved by the degree that the fuel may have a better emission profile if correctly formulated.
Any refining, mining, pumping or transporting or handling of biomass or coal will have a CO2 factor no matter how cleverly it is spruked.


I agree mostly with you, but if biomass is used with CCS, part of its original carbon will end up in the fuel and thus in the atmosphere, but part of the carbon will be sequestered. So, since in conventional BTL-FT only 1 out of 3 carbon atoms endus up as fuel, 2/3 of the carbon could be sequestered, making it a real CO2-negative fuel.

Roger K. Brown

This statement is incorrect. If you read the NREL final report on their experimental program to produce bio-oil from algae you will see than continuous injection of CO2 into the algal ponds was a key factor in achieving high yields.


No, the statement IS correct. I said plants can easily take all the CO2 they NEED from the air - keyword is need. And in that same post I allowed for increased yield if you add CO2.


@Alain "but part of the carbon will be sequestered"

But for how long? Its easy enough to keep carbon underground if it's in the form of a heavy liquid or solid but CO2 is a gas. Most of ideas for sequestering I've seen have a dwell time of less than 100 years. Turning CO2 back into a solid or liquid would keep it there longer but it also takes back the energy you got from turning it into a gas in the first place.

Roger K. Brown

If you want to act like a lawyer two can play that game. Here is your complete quote with the part you are ignoring in bold letters:


The clear implication of this statement is that extra CO2 is a minor element of achieving high yields from algae. This statement is incorrect.


No not a minor element but rather one, that because it can be supply in bulk, isn't the limiting factor. The real limit to plant growth is the shortage of other things- like water[for land plants], fixed nitrogen, trace elements, etc. because these are often harder to come by than CO2.


But if the yield is uneconomic without the added CO2, you're making false claims.

Even 30% less emissions from the cycle is nowhere near the 80% reduction that we need at a minimum to stabilize the atmosphere.  On top of this, the $100k/bbl/day cost is far higher than other options, including tar sands.  CTL is a loser no matter how you cut it.


Yes E.P there is a downgrade to carbon cycle efficiency if 'some ' C is supplied from fossil fuel.
The ideal situation being removal from the atmosphere.

There is a requirement for all nutrients to be supplied in a closed reactor system The atmosphere can supply gaseous elements via agitators or in open or closed systems, with more diverse extended flowing systems, IE a river or race, turbulence could be enhanced for regulation Many inputs are 'normally' existent from various pathways.
The flow might be intercepted periodically at high analysis points.
Highly artificial flows abound in our modified environment. These could be pre -treated ingested and post treated without recourse to fossil fuel inputs.

Might I suggest that if a water course is intercept then the amount of sunlight harvested is effectively that area preceding the harvest point at the growth rate for that part of the system. The analogy is harvesting an unfarmed resource at an intercept.
Ensuring that only target species are gathered would need innovative solution. Bypass, screening, settling ponds or extraction process may offer good separation.

There are hundreds of algal strains including many examples of high productivity without intentional cultivation.
If existing urban and agricultural discharge that ultimately finds natural water flows were 'farmed', a comprehensive monitoring an evaluation could be the main activity.
Although any commercialising of waterways is inherently problematic, such a program would offer the monitoring and solution to a current circumstance where neither now exist.
It is simplistic to suggest that one 'undescribed' example can be a representative model.


@ai vin,
at high pressure (50 bar), CO2 becomes a liquid, which is heavier than water, so you could inject it into underground lakes.
Anyway, CO2 is much less volatile than natural gas, and reacts much easier with all kinds of minerals than natural gas. so, any place where natural gas remains underground (for milions of years), you could inject the CO2.
secondly, in the underground, if the CO2 is in contact with water, it will form H2CO3 which reacts with many minerals to solid carbonates. (in the stones on the earth surface, most rocks are carbonised already, but a large part of the earth mantle is compesed of oxides of Mg and Ca, which easily react with H2CO3 in it is humid.


I guess this has potential relevance for long haul transport and aviation which will be burning liquid fuels for a while until we figure out how to change their engines, but for conventional passenger transportation that you and I do, I have to wonder if it`s all really worth the effort. Won`t electric cars be out if force before this ever comes to fruition?

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