University of Calgary climate change scientist David Keith and his team are working to efficiently capture the greenhouse gas carbon dioxide directly from the air, using near-commercial technology.
In research conducted at the U of C, Keith and a team of researchers showed it is possible to reduce carbon dioxide (CO2) – the main greenhouse gas that contributes to global warming – using a relatively simple machine that can capture the trace amount of CO2 present in the air at any place on the planet.
...Keith and his team showed they could capture CO2 directly from the air with less than 100 kilowatt-hours of electricity per tonne of carbon dioxide. Their custom-built tower was able to capture the equivalent of about 20 tonnes per year of CO2 on a single square metre of scrubbing material – the average amount of emissions that one person produces each year in the North American-wide economy.
That 100 kwh per removed tonne of CO2 would be pretty good in terms of energy cost. If the electricity cost only 10 cents per kwh then the cost per tonne would be only $10. Some proposed carbon tax regimes are at $30 per tonne and up. This could be done with photovoltaics once PV becomes cheap enough. The fact that the sun doesn't shine all the time won't matter. Just run the process when the power is available. No need for transmission lines or even expensive circuitry to convert the electricity into AC power. Though materials costs and piping the CO2 somewhere might add substantial costs.
"This means that if you used electricity from a coal-fired power plant, for every unit of electricity you used to operate the capture machine, you'd be capturing 10 times as much CO2 as the power plant emitted making that much electricity," Keith says.
The U of C team has devised a new way to apply a chemical process derived from the pulp and paper industry cut the energy cost of air capture in half, and has filed two provisional patents on their end-to-end air capture system.
The technology is still in its early stage, Keith stresses. "It now looks like we could capture CO2 from the air with an energy demand comparable to that needed for CO2 capture from conventional power plants, although costs will certainly be higher and there are many pitfalls along the path to commercialization."
What I'd like to see: Use sunlight to drive an artificial photosynthesis process that will fix hydrogen from water to CO2 from the atmosphere. The output would be hydrocarbons usable to power cars and for other purposes. All this will come with time.
Update: See the comment by Bruce Dunn. Looks like the energy for the initial CO2 capture is a small fraction of the total amount of energy needed for this method. So this looks like a bad idea.
By Randall Parker at 2008 September 29 10:36 PM Energy Solar | TrackBackUm, it seems to me we're just reinventing the wheel here to some extent. Don't plants already capture CO2 and output O2? Sure they also output some CO2 but the there is net capturing of CO2 overall, and no man made electrical energy is required - there ends my memory of school level science/biology. So could the answer be lets grow more plants & protect our forests?
I do however like the idea of fixing hydrogen to CO2 to form hydrocarbons whether we use technology or biology or a combination to do this may open a different debate.
Ideas from a novice....
Hyperion makes a reactor that produces electricity for 5 cents kwh.It has been recently report th that water hydrolysis can be be done at 100% efficiency by use of copper nano particles.There has also been progress in catalytic reactors to convert gases into liquids.So there you have it.Now if only we could find a way to make chocolate for $5 a ton.
I couldn't get the PDF to load at any reasonable speed. But it looks as if their capture of the CO2 is much more complex than the article hints. And once you have it you have to get rid of it. Hence use it or bury it.
Even so, if you really want CO2 then this will get it at less, supposedly, cost than present methods.
I would much rather see nuclear grow to dominate electrical generation. The CO2 problem, whatever its scope, will take care of itself as we reduce fossil fuel use.
What happened to all that recent excitement about the capture of CO2 in cement?
The research group has investigated capturing CO2 using a solution of sodium hydroxide and a reaction tower. The sodium hydroxide is either sprayed into the air, or trickled over a packing, while air is moved through the column with fans. The quoted 100 KWhr of electricity to capture 1 ton of CO2 is only the electricity needed to power the fans and pumps to run the tower. The resulting sodium carbonate solution must then be regenerated to NaOH with the release of CO2. This is the real energy intensive phase. They have examined reactions involving either CaOH or a sodium tri-titanate. Either reaction sequence involves heating solid chemicals to about 850 C and then adding large amounts of energy at that temperature to release the CO2. Their estimate of energy requirements for the sodium tri-titanate procedure is 3 GJ per ton of CO2, which translates into an additional 833 KWhr (note however that this is thermal energy, not electricity). Finally, energy is required to compress CO2 and move it to wherever it is to be stored underground.
Everybody should just breathe *in* for one day and not exhale. Problem solved! Along with over-population and several other BS ecotastrophes.
Bruce Dunn,
Sounds like this technology could be sited to work in combination with nuclear and other large power plants that generate large amounts of waste heat. No?
I wonder if this could be used to capture methane gas using less energy than the captured methane could generate in an efficient natural gas power plant? If so, you get a nice twofer. Greenhouse gas reduction and unlimited gas supplies.
If you could scale it way down and speed it up, maybe you could power your car off atmospheric methane. Fun to speculate.
Food for Thought:
Carbon Sequestration in Agriculture and Forestry (http://www.epa.gov/sequestration/faq.html)
4. How much carbon can agricultural and forestry practices sequester?
Carbon sequestration rates vary by tree species, soil type, regional climate, topography and management practice. In the U.S., fairly well-established values for carbon sequestration rates are available for most tree species. Soil carbon sequestration rates vary by soil type and cropping practice and are less well documented but information and research in this area is growing rapidly.
Pine plantations in the Southeast can accumulate almost 100 metric tons of carbon per acre after 90 years, or roughly one metric ton of carbon per acre per year (Birdsey 1996). Changes in forest management (e.g., lengthening the harvest-regeneration cycle) generally result in less carbon sequestration on a per acre basis. Changes in cropping practices, such as from conventional to conservation tillage, have been shown to sequester about 0.1 – 0.3 metric tons of carbon per acre per year (Lal et al. 1999; West and Post 2002). However, a more comprehensive picture of the climate effects of these practices needs to also consider possible nitrous oxide (N2O) and methane (CH4) emissions. (See also FAQ #8)
Carbon accumulation in forests and soils eventually reaches a saturation point, beyond which additional sequestration is no longer possible. This happens, for example, when trees reach maturity, or when the organic matter in soils builds back up to original levels before losses occurred. Even after saturation, the trees or agricultural practices would need to be sustained to maintain the accumulated carbon and prevent subsequent losses of carbon back to the atmosphere.
I know what we need to do:
Plant trees, let them grow for 15 to 60 years, depending upon species, and then harvest the trees.
You then need to store the wood produced to keep it from decomposing and re-emitting CO2 into the air.
One good storage technique is to take the wood and build houses.
Then make sure the houses are left standing for more than twice the harvest timeline to produce a net CO2 air reduction.
Brilliant, eh?
It gets even better. How about producing fuel from the CO2 in the atmosphere? Check out "Green Freedom": http://www.lanl.gov/news/index.php/fuseaction/home.story/story_id/12554
Ed Holston has it exactly right. You can take the waste heat from any power generation process, reconstitute and capture the CO2, then use the excess generating capacity at the nuke plant through night hours to react with water and create syngas, which then turns into methanol to run any flex fuel car (see Bob Zubrin's writings). Eventually we will be able operate virtually all medium range (less than 200 miles a day) and local transportation on methanol created out of water and the air.
This is discussed in Nobel laureate George Olah's excellent book "The Methanol Economy". Prof. Olah runs the hydrocarbons institute at USC.
You can also use the CO2 to fertilize oil algae growth adjacent to power plants. There is no reason whatever to look for places to inject CO2 into the ground- it can all be recycled into liquid fuels pretty easily.
Sodium hydroxide is probably a bad absorbant for atmospheric CO2, since the binding energy is too high (making regeneration more expensive).
There is some work on making ionic liquids that are selective for CO2 absorption. Since there are something like 10^18 different ionic liquids that can be synthesized, there's a lot of room in the search space to find ones with binding energy tuned to an optimal value. These liquids are known for having negligible vapor pressures, which would minimize loss to evaporation.